* [RFC PATCH v2 01/14] slub: Add isolate() and migrate() methods
2019-04-03 4:21 [RFC PATCH v2 00/14] Slab Movable Objects (SMO) Tobin C. Harding
@ 2019-04-03 4:21 ` Tobin C. Harding
2019-04-03 4:21 ` [RFC PATCH v2 02/14] tools/vm/slabinfo: Add support for -C and -M options Tobin C. Harding
` (12 subsequent siblings)
13 siblings, 0 replies; 28+ messages in thread
From: Tobin C. Harding @ 2019-04-03 4:21 UTC (permalink / raw)
To: Andrew Morton
Cc: Tobin C. Harding, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel
Add the two methods needed for moving objects and enable the display of
the callbacks via the /sys/kernel/slab interface.
Add documentation explaining the use of these methods and the prototypes
for slab.h. Add functions to setup the callbacks method for a slab
cache.
Add empty functions for SLAB/SLOB. The API is generic so it could be
theoretically implemented for these allocators as well.
Change sysfs 'ctor' field to be 'ops' to contain all the callback
operations defined for a slab cache. Display the existing 'ctor'
callback in the ops fields contents along with 'isolate' and 'migrate'
callbacks.
Co-developed-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
---
include/linux/slab.h | 70 ++++++++++++++++++++++++++++++++++++++++
include/linux/slub_def.h | 3 ++
mm/slub.c | 59 +++++++++++++++++++++++++++++----
3 files changed, 126 insertions(+), 6 deletions(-)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 9449b19c5f10..886fc130334d 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -154,6 +154,76 @@ void memcg_create_kmem_cache(struct mem_cgroup *, struct kmem_cache *);
void memcg_deactivate_kmem_caches(struct mem_cgroup *);
void memcg_destroy_kmem_caches(struct mem_cgroup *);
+/*
+ * Function prototypes passed to kmem_cache_setup_mobility() to enable
+ * mobile objects and targeted reclaim in slab caches.
+ */
+
+/**
+ * typedef kmem_cache_isolate_func - Object migration callback function.
+ * @s: The cache we are working on.
+ * @ptr: Pointer to an array of pointers to the objects to isolate.
+ * @nr: Number of objects in @ptr array.
+ *
+ * The purpose of kmem_cache_isolate_func() is to pin each object so that
+ * they cannot be freed until kmem_cache_migrate_func() has processed
+ * them. This may be accomplished by increasing the refcount or setting
+ * a flag.
+ *
+ * The object pointer array passed is also passed to
+ * kmem_cache_migrate_func(). The function may remove objects from the
+ * array by setting pointers to %NULL. This is useful if we can
+ * determine that an object is being freed because
+ * kmem_cache_isolate_func() was called when the subsystem was calling
+ * kmem_cache_free(). In that case it is not necessary to increase the
+ * refcount or specially mark the object because the release of the slab
+ * lock will lead to the immediate freeing of the object.
+ *
+ * Context: Called with locks held so that the slab objects cannot be
+ * freed. We are in an atomic context and no slab operations
+ * may be performed.
+ * Return: A pointer that is passed to the migrate function. If any
+ * objects cannot be touched at this point then the pointer may
+ * indicate a failure and then the migration function can simply
+ * remove the references that were already obtained. The private
+ * data could be used to track the objects that were already pinned.
+ */
+typedef void *kmem_cache_isolate_func(struct kmem_cache *s, void **ptr, int nr);
+
+/**
+ * typedef kmem_cache_migrate_func - Object migration callback function.
+ * @s: The cache we are working on.
+ * @ptr: Pointer to an array of pointers to the objects to migrate.
+ * @nr: Number of objects in @ptr array.
+ * @node: The NUMA node where the object should be allocated.
+ * @private: The pointer returned by kmem_cache_isolate_func().
+ *
+ * This function is responsible for migrating objects. Typically, for
+ * each object in the input array you will want to allocate an new
+ * object, copy the original object, update any pointers, and free the
+ * old object.
+ *
+ * After this function returns all pointers to the old object should now
+ * point to the new object.
+ *
+ * Context: Called with no locks held and interrupts enabled. Sleeping
+ * is possible. Any operation may be performed.
+ */
+typedef void kmem_cache_migrate_func(struct kmem_cache *s, void **ptr,
+ int nr, int node, void *private);
+
+/*
+ * kmem_cache_setup_mobility() is used to setup callbacks for a slab cache.
+ */
+#ifdef CONFIG_SLUB
+void kmem_cache_setup_mobility(struct kmem_cache *, kmem_cache_isolate_func,
+ kmem_cache_migrate_func);
+#else
+static inline void
+kmem_cache_setup_mobility(struct kmem_cache *s, kmem_cache_isolate_func isolate,
+ kmem_cache_migrate_func migrate) {}
+#endif
+
/*
* Please use this macro to create slab caches. Simply specify the
* name of the structure and maybe some flags that are listed above.
diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index d2153789bd9f..2879a2f5f8eb 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -99,6 +99,9 @@ struct kmem_cache {
gfp_t allocflags; /* gfp flags to use on each alloc */
int refcount; /* Refcount for slab cache destroy */
void (*ctor)(void *);
+ kmem_cache_isolate_func *isolate;
+ kmem_cache_migrate_func *migrate;
+
unsigned int inuse; /* Offset to metadata */
unsigned int align; /* Alignment */
unsigned int red_left_pad; /* Left redzone padding size */
diff --git a/mm/slub.c b/mm/slub.c
index d30ede89f4a6..ae44d640b8c1 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4326,6 +4326,33 @@ int __kmem_cache_create(struct kmem_cache *s, slab_flags_t flags)
return err;
}
+void kmem_cache_setup_mobility(struct kmem_cache *s,
+ kmem_cache_isolate_func isolate,
+ kmem_cache_migrate_func migrate)
+{
+ /*
+ * Mobile objects must have a ctor otherwise the object may be
+ * in an undefined state on allocation. Since the object may
+ * need to be inspected by the migration function at any time
+ * after allocation we must ensure that the object always has a
+ * defined state.
+ */
+ if (!s->ctor) {
+ pr_err("%s: require constructor to setup mobility\n", s->name);
+ return;
+ }
+
+ s->isolate = isolate;
+ s->migrate = migrate;
+
+ /*
+ * Sadly serialization requirements currently mean that we have
+ * to disable fast cmpxchg based processing.
+ */
+ s->flags &= ~__CMPXCHG_DOUBLE;
+}
+EXPORT_SYMBOL(kmem_cache_setup_mobility);
+
void *__kmalloc_track_caller(size_t size, gfp_t gfpflags, unsigned long caller)
{
struct kmem_cache *s;
@@ -5010,13 +5037,33 @@ static ssize_t cpu_partial_store(struct kmem_cache *s, const char *buf,
}
SLAB_ATTR(cpu_partial);
-static ssize_t ctor_show(struct kmem_cache *s, char *buf)
+static int op_show(char *buf, const char *txt, unsigned long addr)
{
- if (!s->ctor)
- return 0;
- return sprintf(buf, "%pS\n", s->ctor);
+ int x = 0;
+
+ x += sprintf(buf, "%s : ", txt);
+ x += sprint_symbol(buf + x, addr);
+ x += sprintf(buf + x, "\n");
+
+ return x;
+}
+
+static ssize_t ops_show(struct kmem_cache *s, char *buf)
+{
+ int x = 0;
+
+ if (s->ctor)
+ x += op_show(buf + x, "ctor", (unsigned long)s->ctor);
+
+ if (s->isolate)
+ x += op_show(buf + x, "isolate", (unsigned long)s->isolate);
+
+ if (s->migrate)
+ x += op_show(buf + x, "migrate", (unsigned long)s->migrate);
+
+ return x;
}
-SLAB_ATTR_RO(ctor);
+SLAB_ATTR_RO(ops);
static ssize_t aliases_show(struct kmem_cache *s, char *buf)
{
@@ -5429,7 +5476,7 @@ static struct attribute *slab_attrs[] = {
&objects_partial_attr.attr,
&partial_attr.attr,
&cpu_slabs_attr.attr,
- &ctor_attr.attr,
+ &ops_attr.attr,
&aliases_attr.attr,
&align_attr.attr,
&hwcache_align_attr.attr,
--
2.21.0
^ permalink raw reply related [flat|nested] 28+ messages in thread* [RFC PATCH v2 02/14] tools/vm/slabinfo: Add support for -C and -M options
2019-04-03 4:21 [RFC PATCH v2 00/14] Slab Movable Objects (SMO) Tobin C. Harding
2019-04-03 4:21 ` [RFC PATCH v2 01/14] slub: Add isolate() and migrate() methods Tobin C. Harding
@ 2019-04-03 4:21 ` Tobin C. Harding
2019-04-03 4:21 ` [RFC PATCH v2 03/14] slub: Sort slab cache list Tobin C. Harding
` (11 subsequent siblings)
13 siblings, 0 replies; 28+ messages in thread
From: Tobin C. Harding @ 2019-04-03 4:21 UTC (permalink / raw)
To: Andrew Morton
Cc: Tobin C. Harding, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel
-C lists caches that use a ctor.
-M lists caches that support object migration.
Add command line options to show caches with a constructor and caches
that are movable (i.e. have migrate function).
Co-developed-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
---
tools/vm/slabinfo.c | 40 ++++++++++++++++++++++++++++++++++++----
1 file changed, 36 insertions(+), 4 deletions(-)
diff --git a/tools/vm/slabinfo.c b/tools/vm/slabinfo.c
index 73818f1b2ef8..cbfc56c44c2f 100644
--- a/tools/vm/slabinfo.c
+++ b/tools/vm/slabinfo.c
@@ -33,6 +33,7 @@ struct slabinfo {
unsigned int hwcache_align, object_size, objs_per_slab;
unsigned int sanity_checks, slab_size, store_user, trace;
int order, poison, reclaim_account, red_zone;
+ int movable, ctor;
unsigned long partial, objects, slabs, objects_partial, objects_total;
unsigned long alloc_fastpath, alloc_slowpath;
unsigned long free_fastpath, free_slowpath;
@@ -67,6 +68,8 @@ int show_report;
int show_alias;
int show_slab;
int skip_zero = 1;
+int show_movable;
+int show_ctor;
int show_numa;
int show_track;
int show_first_alias;
@@ -109,11 +112,13 @@ static void fatal(const char *x, ...)
static void usage(void)
{
- printf("slabinfo 4/15/2011. (c) 2007 sgi/(c) 2011 Linux Foundation.\n\n"
- "slabinfo [-aADefhilnosrStTvz1LXBU] [N=K] [-dafzput] [slab-regexp]\n"
+ printf("slabinfo 4/15/2017. (c) 2007 sgi/(c) 2011 Linux Foundation/(c) 2017 Jump Trading LLC.\n\n"
+ "slabinfo [-aACDefhilMnosrStTvz1LXBU] [N=K] [-dafzput] [slab-regexp]\n"
+
"-a|--aliases Show aliases\n"
"-A|--activity Most active slabs first\n"
"-B|--Bytes Show size in bytes\n"
+ "-C|--ctor Show slabs with ctors\n"
"-D|--display-active Switch line format to activity\n"
"-e|--empty Show empty slabs\n"
"-f|--first-alias Show first alias\n"
@@ -121,6 +126,7 @@ static void usage(void)
"-i|--inverted Inverted list\n"
"-l|--slabs Show slabs\n"
"-L|--Loss Sort by loss\n"
+ "-M|--movable Show caches that support movable objects\n"
"-n|--numa Show NUMA information\n"
"-N|--lines=K Show the first K slabs\n"
"-o|--ops Show kmem_cache_ops\n"
@@ -588,6 +594,12 @@ static void slabcache(struct slabinfo *s)
if (show_empty && s->slabs)
return;
+ if (show_ctor && !s->ctor)
+ return;
+
+ if (show_movable && !s->movable)
+ return;
+
if (sort_loss == 0)
store_size(size_str, slab_size(s));
else
@@ -602,6 +614,10 @@ static void slabcache(struct slabinfo *s)
*p++ = '*';
if (s->cache_dma)
*p++ = 'd';
+ if (s->ctor)
+ *p++ = 'C';
+ if (s->movable)
+ *p++ = 'M';
if (s->hwcache_align)
*p++ = 'A';
if (s->poison)
@@ -636,7 +652,8 @@ static void slabcache(struct slabinfo *s)
printf("%-21s %8ld %7d %15s %14s %4d %1d %3ld %3ld %s\n",
s->name, s->objects, s->object_size, size_str, dist_str,
s->objs_per_slab, s->order,
- s->slabs ? (s->partial * 100) / s->slabs : 100,
+ s->slabs ? (s->partial * 100) /
+ (s->slabs * s->objs_per_slab) : 100,
s->slabs ? (s->objects * s->object_size * 100) /
(s->slabs * (page_size << s->order)) : 100,
flags);
@@ -1256,6 +1273,13 @@ static void read_slab_dir(void)
slab->alloc_node_mismatch = get_obj("alloc_node_mismatch");
slab->deactivate_bypass = get_obj("deactivate_bypass");
chdir("..");
+ if (read_slab_obj(slab, "ops")) {
+ if (strstr(buffer, "ctor :"))
+ slab->ctor = 1;
+ if (strstr(buffer, "migrate :"))
+ slab->movable = 1;
+ }
+
if (slab->name[0] == ':')
alias_targets++;
slab++;
@@ -1332,6 +1356,8 @@ static void xtotals(void)
}
struct option opts[] = {
+ { "ctor", no_argument, NULL, 'C' },
+ { "movable", no_argument, NULL, 'M' },
{ "aliases", no_argument, NULL, 'a' },
{ "activity", no_argument, NULL, 'A' },
{ "debug", optional_argument, NULL, 'd' },
@@ -1367,7 +1393,7 @@ int main(int argc, char *argv[])
page_size = getpagesize();
- while ((c = getopt_long(argc, argv, "aAd::Defhil1noprstvzTSN:LXBU",
+ while ((c = getopt_long(argc, argv, "aACd::Defhil1MnoprstvzTSN:LXBU",
opts, NULL)) != -1)
switch (c) {
case '1':
@@ -1376,6 +1402,9 @@ int main(int argc, char *argv[])
case 'a':
show_alias = 1;
break;
+ case 'C':
+ show_ctor = 1;
+ break;
case 'A':
sort_active = 1;
break;
@@ -1399,6 +1428,9 @@ int main(int argc, char *argv[])
case 'i':
show_inverted = 1;
break;
+ case 'M':
+ show_movable = 1;
+ break;
case 'n':
show_numa = 1;
break;
--
2.21.0
^ permalink raw reply related [flat|nested] 28+ messages in thread* [RFC PATCH v2 03/14] slub: Sort slab cache list
2019-04-03 4:21 [RFC PATCH v2 00/14] Slab Movable Objects (SMO) Tobin C. Harding
2019-04-03 4:21 ` [RFC PATCH v2 01/14] slub: Add isolate() and migrate() methods Tobin C. Harding
2019-04-03 4:21 ` [RFC PATCH v2 02/14] tools/vm/slabinfo: Add support for -C and -M options Tobin C. Harding
@ 2019-04-03 4:21 ` Tobin C. Harding
2019-04-03 4:21 ` [RFC PATCH v2 04/14] slub: Slab defrag core Tobin C. Harding
` (10 subsequent siblings)
13 siblings, 0 replies; 28+ messages in thread
From: Tobin C. Harding @ 2019-04-03 4:21 UTC (permalink / raw)
To: Andrew Morton
Cc: Tobin C. Harding, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel
It is advantageous to have all defragmentable slabs together at the
beginning of the list of slabs so that there is no need to scan the
complete list. Put defragmentable caches first when adding a slab cache
and others last.
Co-developed-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
---
mm/slab_common.c | 2 +-
mm/slub.c | 6 ++++++
2 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 58251ba63e4a..db5e9a0b1535 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -393,7 +393,7 @@ static struct kmem_cache *create_cache(const char *name,
goto out_free_cache;
s->refcount = 1;
- list_add(&s->list, &slab_caches);
+ list_add_tail(&s->list, &slab_caches);
memcg_link_cache(s);
out:
if (err)
diff --git a/mm/slub.c b/mm/slub.c
index ae44d640b8c1..f6b0e4a395ef 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4342,6 +4342,8 @@ void kmem_cache_setup_mobility(struct kmem_cache *s,
return;
}
+ mutex_lock(&slab_mutex);
+
s->isolate = isolate;
s->migrate = migrate;
@@ -4350,6 +4352,10 @@ void kmem_cache_setup_mobility(struct kmem_cache *s,
* to disable fast cmpxchg based processing.
*/
s->flags &= ~__CMPXCHG_DOUBLE;
+
+ list_move(&s->list, &slab_caches); /* Move to top */
+
+ mutex_unlock(&slab_mutex);
}
EXPORT_SYMBOL(kmem_cache_setup_mobility);
--
2.21.0
^ permalink raw reply related [flat|nested] 28+ messages in thread* [RFC PATCH v2 04/14] slub: Slab defrag core
2019-04-03 4:21 [RFC PATCH v2 00/14] Slab Movable Objects (SMO) Tobin C. Harding
` (2 preceding siblings ...)
2019-04-03 4:21 ` [RFC PATCH v2 03/14] slub: Sort slab cache list Tobin C. Harding
@ 2019-04-03 4:21 ` Tobin C. Harding
2019-04-03 4:21 ` [RFC PATCH v2 05/14] tools/vm/slabinfo: Add remote node defrag ratio output Tobin C. Harding
` (9 subsequent siblings)
13 siblings, 0 replies; 28+ messages in thread
From: Tobin C. Harding @ 2019-04-03 4:21 UTC (permalink / raw)
To: Andrew Morton
Cc: Tobin C. Harding, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel
Internal fragmentation can occur within pages used by the slub
allocator. Under some workloads large numbers of pages can be used by
partial slab pages. This under-utilisation is bad simply because it
wastes memory but also because if the system is under memory pressure
higher order allocations may become difficult to satisfy. If we can
defrag slab caches we can alleviate these problems.
Implement Slab Movable Objects in order to defragment slab caches.
Slab defragmentation may occur:
1. Unconditionally when __kmem_cache_shrink() is called on a slab cache
by the kernel calling kmem_cache_shrink().
2. Unconditionally through the use of the slabinfo command.
slabinfo <cache> -s
3. Conditionally via the use of kmem_cache_defrag()
- Use Slab Movable Objects when shrinking cache.
Currently when the kernel calls kmem_cache_shrink() we curate the
partial slabs list. If object migration is not enabled for the cache we
still do this, if however, SMO is enabled we attempt to move objects in
partially full slabs in order to defragment the cache. Shrink attempts
to move all objects in order to reduce the cache to a single partial
slab for each node.
- Add conditional per node defrag via new function:
kmem_defrag_slabs(int node).
kmem_defrag_slabs() attempts to defragment all slab caches for node.
Defragmentation is done conditionally dependent on MAX_PARTIAL _AND_
defrag_used_ratio.
Caches are only considered for defragmentation if the number of
partial slabs exceeds MAX_PARTIAL (per node).
Also, defragmentation only occurs if the usage ratio of the slab is
lower than the configured percentage (sysfs field added in this
patch). Fragmentation ratios are measured by calculating the
percentage of objects in use compared to the total number of objects
that the slab page can accommodate.
The scanning of slab caches is optimized because the defragmentable
slabs come first on the list. Thus we can terminate scans on the
first slab encountered that does not support defragmentation.
kmem_defrag_slabs() takes a node parameter. This can either be -1 if
defragmentation should be performed on all nodes, or a node number.
Defragmentation may be disabled by setting defrag ratio to 0
echo 0 > /sys/kernel/slab/<cache>/defrag_used_ratio
- Add a defrag ratio sysfs field and set it to 30% by default. A limit
of 30% specifies that more than 3 out of 10 available slots for objects
need to be in use otherwise slab defragmentation will be attempted on
the remaining objects.
In order for a cache to be defragmentable the cache must support object
migration (SMO). Enabling SMO for a cache is done via a call to the
recently added function:
void kmem_cache_setup_mobility(struct kmem_cache *,
kmem_cache_isolate_func,
kmem_cache_migrate_func);
Co-developed-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
---
Documentation/ABI/testing/sysfs-kernel-slab | 14 +
include/linux/slab.h | 1 +
include/linux/slub_def.h | 7 +
mm/slub.c | 385 ++++++++++++++++----
4 files changed, 334 insertions(+), 73 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-kernel-slab b/Documentation/ABI/testing/sysfs-kernel-slab
index 29601d93a1c2..7770c03be6b4 100644
--- a/Documentation/ABI/testing/sysfs-kernel-slab
+++ b/Documentation/ABI/testing/sysfs-kernel-slab
@@ -180,6 +180,20 @@ Description:
list. It can be written to clear the current count.
Available when CONFIG_SLUB_STATS is enabled.
+What: /sys/kernel/slab/cache/defrag_used_ratio
+Date: February 2019
+KernelVersion: 5.0
+Contact: Christoph Lameter <cl@linux-foundation.org>
+ Pekka Enberg <penberg@cs.helsinki.fi>,
+Description:
+ The defrag_used_ratio file allows the control of how aggressive
+ slab fragmentation reduction works at reclaiming objects from
+ sparsely populated slabs. This is a percentage. If a slab has
+ less than this percentage of objects allocated then reclaim will
+ attempt to reclaim objects so that the whole slab page can be
+ freed. 0% specifies no reclaim attempt (defrag disabled), 100%
+ specifies attempt to reclaim all pages. The default is 30%.
+
What: /sys/kernel/slab/cache/deactivate_to_tail
Date: February 2008
KernelVersion: 2.6.25
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 886fc130334d..4bf381b34829 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -149,6 +149,7 @@ struct kmem_cache *kmem_cache_create_usercopy(const char *name,
void (*ctor)(void *));
void kmem_cache_destroy(struct kmem_cache *);
int kmem_cache_shrink(struct kmem_cache *);
+unsigned long kmem_defrag_slabs(int node);
void memcg_create_kmem_cache(struct mem_cgroup *, struct kmem_cache *);
void memcg_deactivate_kmem_caches(struct mem_cgroup *);
diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index 2879a2f5f8eb..34c6f1250652 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -107,6 +107,13 @@ struct kmem_cache {
unsigned int red_left_pad; /* Left redzone padding size */
const char *name; /* Name (only for display!) */
struct list_head list; /* List of slab caches */
+ int defrag_used_ratio; /*
+ * Ratio used to check against the
+ * percentage of objects allocated in a
+ * slab page. If less than this ratio
+ * is allocated then reclaim attempts
+ * are made.
+ */
#ifdef CONFIG_SYSFS
struct kobject kobj; /* For sysfs */
struct work_struct kobj_remove_work;
diff --git a/mm/slub.c b/mm/slub.c
index f6b0e4a395ef..e601c804ed79 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -354,6 +354,12 @@ static __always_inline void slab_lock(struct page *page)
bit_spin_lock(PG_locked, &page->flags);
}
+static __always_inline int slab_trylock(struct page *page)
+{
+ VM_BUG_ON_PAGE(PageTail(page), page);
+ return bit_spin_trylock(PG_locked, &page->flags);
+}
+
static __always_inline void slab_unlock(struct page *page)
{
VM_BUG_ON_PAGE(PageTail(page), page);
@@ -3643,6 +3649,7 @@ static int kmem_cache_open(struct kmem_cache *s, slab_flags_t flags)
set_cpu_partial(s);
+ s->defrag_used_ratio = 30;
#ifdef CONFIG_NUMA
s->remote_node_defrag_ratio = 1000;
#endif
@@ -3959,79 +3966,6 @@ void kfree(const void *x)
}
EXPORT_SYMBOL(kfree);
-#define SHRINK_PROMOTE_MAX 32
-
-/*
- * kmem_cache_shrink discards empty slabs and promotes the slabs filled
- * up most to the head of the partial lists. New allocations will then
- * fill those up and thus they can be removed from the partial lists.
- *
- * The slabs with the least items are placed last. This results in them
- * being allocated from last increasing the chance that the last objects
- * are freed in them.
- */
-int __kmem_cache_shrink(struct kmem_cache *s)
-{
- int node;
- int i;
- struct kmem_cache_node *n;
- struct page *page;
- struct page *t;
- struct list_head discard;
- struct list_head promote[SHRINK_PROMOTE_MAX];
- unsigned long flags;
- int ret = 0;
-
- flush_all(s);
- for_each_kmem_cache_node(s, node, n) {
- INIT_LIST_HEAD(&discard);
- for (i = 0; i < SHRINK_PROMOTE_MAX; i++)
- INIT_LIST_HEAD(promote + i);
-
- spin_lock_irqsave(&n->list_lock, flags);
-
- /*
- * Build lists of slabs to discard or promote.
- *
- * Note that concurrent frees may occur while we hold the
- * list_lock. page->inuse here is the upper limit.
- */
- list_for_each_entry_safe(page, t, &n->partial, lru) {
- int free = page->objects - page->inuse;
-
- /* Do not reread page->inuse */
- barrier();
-
- /* We do not keep full slabs on the list */
- BUG_ON(free <= 0);
-
- if (free == page->objects) {
- list_move(&page->lru, &discard);
- n->nr_partial--;
- } else if (free <= SHRINK_PROMOTE_MAX)
- list_move(&page->lru, promote + free - 1);
- }
-
- /*
- * Promote the slabs filled up most to the head of the
- * partial list.
- */
- for (i = SHRINK_PROMOTE_MAX - 1; i >= 0; i--)
- list_splice(promote + i, &n->partial);
-
- spin_unlock_irqrestore(&n->list_lock, flags);
-
- /* Release empty slabs */
- list_for_each_entry_safe(page, t, &discard, lru)
- discard_slab(s, page);
-
- if (slabs_node(s, node))
- ret = 1;
- }
-
- return ret;
-}
-
#ifdef CONFIG_MEMCG
static void kmemcg_cache_deact_after_rcu(struct kmem_cache *s)
{
@@ -4326,6 +4260,287 @@ int __kmem_cache_create(struct kmem_cache *s, slab_flags_t flags)
return err;
}
+/*
+ * Allocate a slab scratch space that is sufficient to keep pointers to
+ * individual objects for all objects in cache and also a bitmap for the
+ * objects (used to mark which objects are active).
+ */
+static inline void *alloc_scratch(struct kmem_cache *s)
+{
+ unsigned int size = oo_objects(s->max);
+
+ return kmalloc(size * sizeof(void *) +
+ BITS_TO_LONGS(size) * sizeof(unsigned long),
+ GFP_KERNEL);
+}
+
+/*
+ * move_slab_page() - Move all objects in the given slab.
+ * @page: The slab we are working on.
+ * @scratch: Pointer to scratch space.
+ * @node: The target node to move objects to.
+ *
+ * If the target node is not the current node then the object is moved
+ * to the target node. If the target node is the current node then this
+ * is an effective way of defragmentation since the current slab page
+ * with its object is exempt from allocation.
+ */
+static void move_slab_page(struct page *page, void *scratch, int node)
+{
+ unsigned long objects;
+ struct kmem_cache *s;
+ unsigned long flags;
+ unsigned long *map;
+ void *private;
+ int count;
+ void *p;
+ void **vector = scratch;
+ void *addr = page_address(page);
+
+ local_irq_save(flags);
+ slab_lock(page);
+
+ BUG_ON(!PageSlab(page)); /* Must be a slab page */
+ BUG_ON(!page->frozen); /* Slab must have been frozen earlier */
+
+ s = page->slab_cache;
+ objects = page->objects;
+ map = scratch + objects * sizeof(void **);
+
+ /* Determine used objects */
+ bitmap_fill(map, objects);
+ for (p = page->freelist; p; p = get_freepointer(s, p))
+ __clear_bit(slab_index(p, s, addr), map);
+
+ /* Build vector of pointers to objects */
+ count = 0;
+ memset(vector, 0, objects * sizeof(void **));
+ for_each_object(p, s, addr, objects)
+ if (test_bit(slab_index(p, s, addr), map))
+ vector[count++] = p;
+
+ if (s->isolate)
+ private = s->isolate(s, vector, count);
+ else
+ /* Objects do not need to be isolated */
+ private = NULL;
+
+ /*
+ * Pinned the objects. Now we can drop the slab lock. The slab
+ * is frozen so it cannot vanish from under us nor will
+ * allocations be performed on the slab. However, unlocking the
+ * slab will allow concurrent slab_frees to proceed. So the
+ * subsystem must have a way to tell from the content of the
+ * object that it was freed.
+ *
+ * If neither RCU nor ctor is being used then the object may be
+ * modified by the allocator after being freed which may disrupt
+ * the ability of the migrate function to tell if the object is
+ * free or not.
+ */
+ slab_unlock(page);
+ local_irq_restore(flags);
+
+ /* Perform callback to move the objects */
+ s->migrate(s, vector, count, node, private);
+}
+
+/*
+ * kmem_cache_defrag() - Defragment node.
+ * @s: cache we are working on.
+ * @node: The node to move objects from.
+ * @target_node: The node to move objects to.
+ * @ratio: The defrag ratio (percentage, between 0 and 100).
+ *
+ * Release slabs with zero objects and try to call the migration function
+ * for slabs with less than the 'ratio' percentage of objects allocated.
+ *
+ * Moved objects are allocated on @target_node.
+ *
+ * Return: The number of partial slabs left on @node after the
+ * operation.
+ */
+static unsigned long kmem_cache_defrag(struct kmem_cache *s,
+ int node, int target_node, int ratio)
+{
+ struct kmem_cache_node *n = get_node(s, node);
+ struct page *page, *page2;
+ LIST_HEAD(move_list);
+ unsigned long flags;
+
+ if (node == target_node && n->nr_partial <= 1) {
+ /*
+ * Trying to reduce fragmentation on a node but there is
+ * only a single or no partial slab page. This is already
+ * the optimal object density that we can reach.
+ */
+ return n->nr_partial;
+ }
+
+ spin_lock_irqsave(&n->list_lock, flags);
+ list_for_each_entry_safe(page, page2, &n->partial, lru) {
+ if (!slab_trylock(page))
+ /* Busy slab. Get out of the way */
+ continue;
+
+ if (page->inuse) {
+ if (page->inuse > ratio * page->objects / 100) {
+ slab_unlock(page);
+ /*
+ * Skip slab because the object density
+ * in the slab page is high enough.
+ */
+ continue;
+ }
+
+ list_move(&page->lru, &move_list);
+ if (s->migrate) {
+ /* Stop page being considered for allocations */
+ n->nr_partial--;
+ page->frozen = 1;
+ }
+ slab_unlock(page);
+ } else { /* Empty slab page */
+ list_del(&page->lru);
+ n->nr_partial--;
+ slab_unlock(page);
+ discard_slab(s, page);
+ }
+ }
+
+ if (!s->migrate) {
+ /*
+ * No defrag method. By simply putting the zaplist at
+ * the end of the partial list we can let them simmer
+ * longer and thus increase the chance of all objects
+ * being reclaimed.
+ */
+ list_splice(&move_list, n->partial.prev);
+ }
+
+ spin_unlock_irqrestore(&n->list_lock, flags);
+
+ if (s->migrate && !list_empty(&move_list)) {
+ void **scratch = alloc_scratch(s);
+ if (scratch) {
+ /* Try to remove / move the objects left */
+ list_for_each_entry(page, &move_list, lru) {
+ if (page->inuse)
+ move_slab_page(page, scratch, target_node);
+ }
+ kfree(scratch);
+ }
+
+ /* Inspect results and dispose of pages */
+ spin_lock_irqsave(&n->list_lock, flags);
+ list_for_each_entry_safe(page, page2, &move_list, lru) {
+ list_del(&page->lru);
+ slab_lock(page);
+ page->frozen = 0;
+
+ if (page->inuse) {
+ /*
+ * Objects left in slab page, move it to the
+ * tail of the partial list to increase the
+ * chance that the freeing of the remaining
+ * objects will free the slab page.
+ */
+ n->nr_partial++;
+ list_add_tail(&page->lru, &n->partial);
+ slab_unlock(page);
+ } else {
+ slab_unlock(page);
+ discard_slab(s, page);
+ }
+ }
+ spin_unlock_irqrestore(&n->list_lock, flags);
+ }
+
+ return n->nr_partial;
+}
+
+/**
+ * kmem_defrag_slabs() - Defrag slab caches.
+ * @node: The node to defrag or -1 for all nodes.
+ *
+ * Defrag slabs conditional on the amount of fragmentation in a page.
+ *
+ * Return: The total number of partial slabs in migratable caches left
+ * on @node after the operation.
+ */
+unsigned long kmem_defrag_slabs(int node)
+{
+ struct kmem_cache *s;
+ unsigned long left = 0;
+ int nid;
+
+ if (node >= MAX_NUMNODES)
+ return -EINVAL;
+
+ /*
+ * kmem_defrag_slabs() may be called from the reclaim path which
+ * may be called for any page allocator alloc. So there is the
+ * danger that we get called in a situation where slub already
+ * acquired the slub_lock for other purposes.
+ */
+ if (!mutex_trylock(&slab_mutex))
+ return 0;
+
+ list_for_each_entry(s, &slab_caches, list) {
+ /*
+ * Defragmentable caches come first. If the slab cache is
+ * not defragmentable then we can stop traversing the list.
+ */
+ if (!s->migrate)
+ break;
+
+ if (node >= 0) {
+ if (s->node[node]->nr_partial > MAX_PARTIAL) {
+ left += kmem_cache_defrag(s, node, node,
+ s->defrag_used_ratio);
+ }
+ continue;
+ }
+
+ for_each_node_state(nid, N_NORMAL_MEMORY) {
+ if (s->node[nid]->nr_partial > MAX_PARTIAL) {
+ left += kmem_cache_defrag(s, nid, nid,
+ s->defrag_used_ratio);
+ }
+ }
+ }
+ mutex_unlock(&slab_mutex);
+ return left;
+}
+EXPORT_SYMBOL(kmem_defrag_slabs);
+
+/**
+ * __kmem_cache_shrink() - Shrink a cache.
+ * @s: The cache to shrink.
+ *
+ * Reduces the memory footprint of a slab cache by as much as possible.
+ *
+ * This works by:
+ * 1. Removing empty slabs from the partial list.
+ * 2. Migrating slab objects to denser slab pages if the slab cache
+ * supports migration. If not, reorganizing the partial list so that
+ * more densely allocated slab pages come first.
+ *
+ * Not called directly, called by kmem_cache_shrink().
+ */
+int __kmem_cache_shrink(struct kmem_cache *s)
+{
+ int node;
+ int left = 0;
+
+ flush_all(s);
+ for_each_node_state(node, N_NORMAL_MEMORY)
+ left += kmem_cache_defrag(s, node, node, 100);
+
+ return left;
+}
+EXPORT_SYMBOL(__kmem_cache_shrink);
+
void kmem_cache_setup_mobility(struct kmem_cache *s,
kmem_cache_isolate_func isolate,
kmem_cache_migrate_func migrate)
@@ -5177,6 +5392,29 @@ static ssize_t destroy_by_rcu_show(struct kmem_cache *s, char *buf)
}
SLAB_ATTR_RO(destroy_by_rcu);
+static ssize_t defrag_used_ratio_show(struct kmem_cache *s, char *buf)
+{
+ return sprintf(buf, "%d\n", s->defrag_used_ratio);
+}
+
+static ssize_t defrag_used_ratio_store(struct kmem_cache *s,
+ const char *buf, size_t length)
+{
+ unsigned long ratio;
+ int err;
+
+ err = kstrtoul(buf, 10, &ratio);
+ if (err)
+ return err;
+
+ if (ratio > 100)
+ return -EINVAL;
+
+ s->defrag_used_ratio = ratio;
+ return length;
+}
+SLAB_ATTR(defrag_used_ratio);
+
#ifdef CONFIG_SLUB_DEBUG
static ssize_t slabs_show(struct kmem_cache *s, char *buf)
{
@@ -5501,6 +5739,7 @@ static struct attribute *slab_attrs[] = {
&validate_attr.attr,
&alloc_calls_attr.attr,
&free_calls_attr.attr,
+ &defrag_used_ratio_attr.attr,
#endif
#ifdef CONFIG_ZONE_DMA
&cache_dma_attr.attr,
--
2.21.0
^ permalink raw reply related [flat|nested] 28+ messages in thread* [RFC PATCH v2 05/14] tools/vm/slabinfo: Add remote node defrag ratio output
2019-04-03 4:21 [RFC PATCH v2 00/14] Slab Movable Objects (SMO) Tobin C. Harding
` (3 preceding siblings ...)
2019-04-03 4:21 ` [RFC PATCH v2 04/14] slub: Slab defrag core Tobin C. Harding
@ 2019-04-03 4:21 ` Tobin C. Harding
2019-04-03 4:21 ` [RFC PATCH v2 06/14] tools/vm/slabinfo: Add defrag_used_ratio output Tobin C. Harding
` (8 subsequent siblings)
13 siblings, 0 replies; 28+ messages in thread
From: Tobin C. Harding @ 2019-04-03 4:21 UTC (permalink / raw)
To: Andrew Morton
Cc: Tobin C. Harding, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel
Add output line for NUMA remote node defrag ratio.
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
---
tools/vm/slabinfo.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/tools/vm/slabinfo.c b/tools/vm/slabinfo.c
index cbfc56c44c2f..d2c22f9ee2d8 100644
--- a/tools/vm/slabinfo.c
+++ b/tools/vm/slabinfo.c
@@ -34,6 +34,7 @@ struct slabinfo {
unsigned int sanity_checks, slab_size, store_user, trace;
int order, poison, reclaim_account, red_zone;
int movable, ctor;
+ int remote_node_defrag_ratio;
unsigned long partial, objects, slabs, objects_partial, objects_total;
unsigned long alloc_fastpath, alloc_slowpath;
unsigned long free_fastpath, free_slowpath;
@@ -377,6 +378,10 @@ static void slab_numa(struct slabinfo *s, int mode)
if (skip_zero && !s->slabs)
return;
+ if (mode) {
+ printf("\nNUMA remote node defrag ratio: %3d\n",
+ s->remote_node_defrag_ratio);
+ }
if (!line) {
printf("\n%-21s:", mode ? "NUMA nodes" : "Slab");
for(node = 0; node <= highest_node; node++)
@@ -1272,6 +1277,8 @@ static void read_slab_dir(void)
slab->cpu_partial_free = get_obj("cpu_partial_free");
slab->alloc_node_mismatch = get_obj("alloc_node_mismatch");
slab->deactivate_bypass = get_obj("deactivate_bypass");
+ slab->remote_node_defrag_ratio =
+ get_obj("remote_node_defrag_ratio");
chdir("..");
if (read_slab_obj(slab, "ops")) {
if (strstr(buffer, "ctor :"))
--
2.21.0
^ permalink raw reply related [flat|nested] 28+ messages in thread* [RFC PATCH v2 06/14] tools/vm/slabinfo: Add defrag_used_ratio output
2019-04-03 4:21 [RFC PATCH v2 00/14] Slab Movable Objects (SMO) Tobin C. Harding
` (4 preceding siblings ...)
2019-04-03 4:21 ` [RFC PATCH v2 05/14] tools/vm/slabinfo: Add remote node defrag ratio output Tobin C. Harding
@ 2019-04-03 4:21 ` Tobin C. Harding
2019-04-03 4:21 ` [RFC PATCH v2 07/14] tools/testing/slab: Add object migration test module Tobin C. Harding
` (7 subsequent siblings)
13 siblings, 0 replies; 28+ messages in thread
From: Tobin C. Harding @ 2019-04-03 4:21 UTC (permalink / raw)
To: Andrew Morton
Cc: Tobin C. Harding, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel
Add output for the newly added defrag_used_ratio sysfs knob.
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
---
tools/vm/slabinfo.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/tools/vm/slabinfo.c b/tools/vm/slabinfo.c
index d2c22f9ee2d8..ef4ff93df4cc 100644
--- a/tools/vm/slabinfo.c
+++ b/tools/vm/slabinfo.c
@@ -34,6 +34,7 @@ struct slabinfo {
unsigned int sanity_checks, slab_size, store_user, trace;
int order, poison, reclaim_account, red_zone;
int movable, ctor;
+ int defrag_used_ratio;
int remote_node_defrag_ratio;
unsigned long partial, objects, slabs, objects_partial, objects_total;
unsigned long alloc_fastpath, alloc_slowpath;
@@ -549,6 +550,8 @@ static void report(struct slabinfo *s)
printf("** Slabs are destroyed via RCU\n");
if (s->reclaim_account)
printf("** Reclaim accounting active\n");
+ if (s->movable)
+ printf("** Defragmentation at %d%%\n", s->defrag_used_ratio);
printf("\nSizes (bytes) Slabs Debug Memory\n");
printf("------------------------------------------------------------------------\n");
@@ -1279,6 +1282,7 @@ static void read_slab_dir(void)
slab->deactivate_bypass = get_obj("deactivate_bypass");
slab->remote_node_defrag_ratio =
get_obj("remote_node_defrag_ratio");
+ slab->defrag_used_ratio = get_obj("defrag_used_ratio");
chdir("..");
if (read_slab_obj(slab, "ops")) {
if (strstr(buffer, "ctor :"))
--
2.21.0
^ permalink raw reply related [flat|nested] 28+ messages in thread* [RFC PATCH v2 07/14] tools/testing/slab: Add object migration test module
2019-04-03 4:21 [RFC PATCH v2 00/14] Slab Movable Objects (SMO) Tobin C. Harding
` (5 preceding siblings ...)
2019-04-03 4:21 ` [RFC PATCH v2 06/14] tools/vm/slabinfo: Add defrag_used_ratio output Tobin C. Harding
@ 2019-04-03 4:21 ` Tobin C. Harding
2019-04-03 4:21 ` [RFC PATCH v2 08/14] tools/testing/slab: Add object migration test suite Tobin C. Harding
` (6 subsequent siblings)
13 siblings, 0 replies; 28+ messages in thread
From: Tobin C. Harding @ 2019-04-03 4:21 UTC (permalink / raw)
To: Andrew Morton
Cc: Tobin C. Harding, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel
We just implemented slab movable objects for the SLUB allocator. We
should test that code. In order to do so we need to be able to do a
number of things
- Create a cache
- Enable Slab Movable Objects for the cache
- Allocate objects to the cache
- Free objects from within specific slabs of the cache
We can do all this via a loadable module.
Add a module that defines functions that can be triggered from userspace
via a debugfs entry. From the source:
/*
* SLUB defragmentation a.k.a. Slab Movable Objects (SMO).
*
* This module is used for testing the SLUB allocator. Enables
* userspace to run kernel functions via a debugfs file.
*
* debugfs: /sys/kernel/debugfs/smo/callfn (write only)
*
* String written to `callfn` is parsed by the module and associated
* function is called. See fn_tab for mapping of strings to functions.
*/
References to allocated objects are kept by the module in a linked list
so that userspace can control which object to free.
We introduce the following four functions via the function table
"enable": Enables object migration for the test cache.
"alloc X": Allocates X objects
"free X [Y]": Frees X objects starting at list position Y (default Y==0)
"test": Runs [stress] tests from within the module (see below).
{"enable", smo_enable_cache_mobility},
{"alloc", smo_alloc_objects},
{"free", smo_free_object},
{"test", smo_run_module_tests},
Freeing from the start of the list creates a hole in the slab being
freed from (i.e. creates a partial slab). The results of running these
commands can be see using `slabinfo` (available in tools/vm/):
make -o slabinfo tools/vm/slabinfo.c
Stress tests can be run from within the module. These tests are
internal to the module because we verify that object references are
still good after object migration. These are called 'stress' tests
because it is intended that they create/free a lot of objects.
Userspace can control the number of objects to create, default is 1000.
Example test session
--------------------
Relevant /proc/slabinfo column headers:
name <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab>
# mount -t debugfs none /sys/kernel/debug/
$ cd path/to/linux/tools/testing/slab; make
...
# insmod slub_defrag.ko
# cat /proc/slabinfo | grep smo_test | sed 's/:.*//'
smo_test 0 0 392 20 2
From this we can see that the module created cache 'smo_test' with 20
objects per slab and 2 pages per slab (and cache is currently empty).
We can play with the slab allocator manually:
# insmod slub_defrag.ko
# echo 'alloc 21' > callfn
# cat /proc/slabinfo | grep smo_test | sed 's/:.*//'
smo_test 21 40 392 20 2
We see here that 21 active objects have been allocated creating 2
slabs (40 total objects).
# slabinfo smo_test --report
Slabcache: smo_test Aliases: 0 Order : 1 Objects: 21
Sizes (bytes) Slabs Debug Memory
------------------------------------------------------------------------
Object : 56 Total : 2 Sanity Checks : On Total: 16384
SlabObj: 392 Full : 1 Redzoning : On Used : 1176
SlabSiz: 8192 Partial: 1 Poisoning : On Loss : 15208
Loss : 336 CpuSlab: 0 Tracking : On Lalig: 7056
Align : 8 Objects: 20 Tracing : Off Lpadd: 704
Now free an object from the first slot of the first slab
# echo 'free 1' > callfn
# cat /proc/slabinfo | grep smo_test | sed 's/:.*//'
smo_test 20 40 392 20 2
# slabinfo smo_test --report
Slabcache: smo_test Aliases: 0 Order : 1 Objects: 20
Sizes (bytes) Slabs Debug Memory
------------------------------------------------------------------------
Object : 56 Total : 2 Sanity Checks : On Total: 16384
SlabObj: 392 Full : 0 Redzoning : On Used : 1120
SlabSiz: 8192 Partial: 2 Poisoning : On Loss : 15264
Loss : 336 CpuSlab: 0 Tracking : On Lalig: 6720
Align : 8 Objects: 20 Tracing : Off Lpadd: 704
Calling shrink now on the cache does nothing because object migration is
not enabled (output omitted). If we enable object migration then shrink
the cache we expect the object from the second slab to me moved to the
first slot in the first slab and the second slab to be removed from the
partial list.
# echo 'enable' > callfn
# slabinfo smo_test --shrink
# slabinfo smo_test --report
Slabcache: smo_test Aliases: 0 Order : 1 Objects: 20
** Defragmentation at 30%
Sizes (bytes) Slabs Debug Memory
------------------------------------------------------------------------
Object : 56 Total : 1 Sanity Checks : On Total: 8192
SlabObj: 392 Full : 1 Redzoning : On Used : 1120
SlabSiz: 8192 Partial: 0 Poisoning : On Loss : 7072
Loss : 336 CpuSlab: 0 Tracking : On Lalig: 6720
Align : 8 Objects: 20 Tracing : Off Lpadd: 352
We can run the stress tests (with the default number of objects):
# cd /sys/kernel/debug/smo
# echo 'test' > callfn
[ 3.576617] smo: test using nr_objs: 1000 keep: 10
[ 3.580169] smo: Module tests completed successfully
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
---
tools/testing/slab/Makefile | 10 +
tools/testing/slab/slub_defrag.c | 566 +++++++++++++++++++++++++++++++
2 files changed, 576 insertions(+)
create mode 100644 tools/testing/slab/Makefile
create mode 100644 tools/testing/slab/slub_defrag.c
diff --git a/tools/testing/slab/Makefile b/tools/testing/slab/Makefile
new file mode 100644
index 000000000000..440c2e3e356f
--- /dev/null
+++ b/tools/testing/slab/Makefile
@@ -0,0 +1,10 @@
+obj-m += slub_defrag.o
+
+KTREE=../../..
+
+all:
+ make -C ${KTREE} M=$(PWD) modules
+
+clean:
+ make -C ${KTREE} M=$(PWD) clean
+
diff --git a/tools/testing/slab/slub_defrag.c b/tools/testing/slab/slub_defrag.c
new file mode 100644
index 000000000000..4a5c24394b96
--- /dev/null
+++ b/tools/testing/slab/slub_defrag.c
@@ -0,0 +1,566 @@
+// SPDX-License-Identifier: GPL-2.0+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/uaccess.h>
+#include <linux/list.h>
+#include <linux/gfp.h>
+#include <linux/debugfs.h>
+#include <linux/numa.h>
+
+/*
+ * SLUB defragmentation a.k.a. Slab Movable Objects (SMO).
+ *
+ * This module is used for testing the SLUB allocator. Enables
+ * userspace to run kernel functions via a debugfs file.
+ *
+ * debugfs: /sys/kernel/debugfs/smo/callfn (write only)
+ *
+ * String written to `callfn` is parsed by the module and associated
+ * function is called. See fn_tab for mapping of strings to functions.
+ */
+
+/* debugfs commands accept two optional arguments */
+#define SMO_CMD_DEFAUT_ARG -1
+
+#define SMO_DEBUGFS_DIR "smo"
+struct dentry *smo_debugfs_root;
+
+#define SMO_CACHE_NAME "smo_test"
+static struct kmem_cache *cachep;
+
+struct smo_slub_object {
+ struct list_head list;
+ char buf[32]; /* Unused except to control size of object */
+ long id;
+};
+
+/* Our list of allocated objects */
+LIST_HEAD(objects);
+
+static void list_add_to_objects(struct smo_slub_object *so)
+{
+ /*
+ * We free from the front of the list so store at the
+ * tail in order to put holes in the cache when we free.
+ */
+ list_add_tail(&so->list, &objects);
+}
+
+/**
+ * smo_object_ctor() - SMO object constructor function.
+ * @ptr: Pointer to memory where the object should be constructed.
+ */
+void smo_object_ctor(void *ptr)
+{
+ struct smo_slub_object *so = ptr;
+
+ INIT_LIST_HEAD(&so->list);
+ memset(so->buf, 0, sizeof(so->buf));
+ so->id = -1;
+}
+
+/**
+ * smo_cache_migrate() - kmem_cache migrate function.
+ * @cp: kmem_cache pointer.
+ * @objs: Array of pointers to objects to migrate.
+ * @size: Number of objects in @objs.
+ * @node: NUMA node where the object should be allocated.
+ * @private: Pointer returned by kmem_cache_isolate_func().
+ */
+void smo_cache_migrate(struct kmem_cache *cp, void **objs, int size,
+ int node, void *private)
+{
+ struct smo_slub_object **so_objs = (struct smo_slub_object **)objs;
+ struct smo_slub_object *so_old, *so_new;
+ int i;
+
+ for (i = 0; i < size; i++) {
+ so_old = so_objs[i];
+
+ so_new = kmem_cache_alloc_node(cachep, GFP_KERNEL, node);
+ if (!so_new) {
+ pr_debug("kmem_cache_alloc failed\n");
+ return;
+ }
+
+ /* Copy object */
+ so_new->id = so_old->id;
+
+ /* Update references to old object */
+ list_del(&so_old->list);
+ list_add_to_objects(so_new);
+
+ kmem_cache_free(cachep, so_old);
+ }
+}
+
+static int smo_enable_cache_mobility(int _unused, int __unused)
+{
+ /* Enable movable objects: BOOM! */
+ kmem_cache_setup_mobility(cachep, NULL, smo_cache_migrate);
+ pr_info("smo: kmem_cache %s defrag enabled\n", SMO_CACHE_NAME);
+ return 0;
+}
+
+/*
+ * smo_alloc_objects() - Allocate objects and store reference.
+ * @nr_objs: Number of objects to allocate.
+ * @node: NUMA node to allocate objects on.
+ *
+ * Allocates @n smo_slub_objects. Stores a reference to them in
+ * the global list of objects (at the tail of the list).
+ *
+ * Return: The number of objects allocated.
+ */
+static int smo_alloc_objects(int nr_objs, int node)
+{
+ struct smo_slub_object *so;
+ int i;
+
+ /* Set sane parameters if no args passed in */
+ if (nr_objs == SMO_CMD_DEFAUT_ARG)
+ nr_objs = 1;
+ if (node == SMO_CMD_DEFAUT_ARG)
+ node = NUMA_NO_NODE;
+
+ for (i = 0; i < nr_objs; i++) {
+ if (node == NUMA_NO_NODE)
+ so = kmem_cache_alloc(cachep, GFP_KERNEL);
+ else
+ so = kmem_cache_alloc_node(cachep, GFP_KERNEL, node);
+ if (!so) {
+ pr_err("smo: Failed to alloc object %d of %d\n", i, nr_objs);
+ return i;
+ }
+ list_add_to_objects(so);
+ }
+ return nr_objs;
+}
+
+/*
+ * smo_free_object() - Frees n objects from position.
+ * @nr_objs: Number of objects to free.
+ * @pos: Position in global list to start freeing.
+ *
+ * Iterates over the global list of objects to position @pos then frees @n
+ * objects from there (or to end of list). Does nothing if @n > list length.
+ *
+ * Calling with @n==0 frees all objects starting at @pos.
+ *
+ * Return: Number of objects freed.
+ */
+static int smo_free_object(int nr_objs, int pos)
+{
+ struct smo_slub_object *cur, *tmp;
+ int deleted = 0;
+ int i = 0;
+
+ /* Set sane parameters if no args passed in */
+ if (nr_objs == SMO_CMD_DEFAUT_ARG)
+ nr_objs = 1;
+ if (pos == SMO_CMD_DEFAUT_ARG)
+ pos = 0;
+
+ list_for_each_entry_safe(cur, tmp, &objects, list) {
+ if (i < pos) {
+ i++;
+ continue;
+ }
+
+ list_del(&cur->list);
+ kmem_cache_free(cachep, cur);
+ deleted++;
+ if (deleted == nr_objs)
+ break;
+ }
+ return deleted;
+}
+
+static int index_for_expected_id(long *expected, int size, long id)
+{
+ int i;
+
+ /* Array is unsorted, just iterate the whole thing */
+ for (i = 0; i < size; i++) {
+ if (expected[i] == id)
+ return i;
+ }
+ return -1; /* Not found */
+}
+
+static int assert_have_objects(int nr_objs, int keep)
+{
+ struct smo_slub_object *cur;
+ long *expected; /* Array of expected IDs */
+ int nr_ids; /* Length of array */
+ long id;
+ int index, i;
+
+ nr_ids = nr_objs / keep + 1;
+
+ expected = kmalloc_array(nr_ids, sizeof(long), GFP_KERNEL);
+ if (!expected)
+ return -ENOMEM;
+
+ id = 0;
+ for (i = 0; i < nr_ids; i++) {
+ expected[i] = id;
+ id += keep;
+ }
+
+ list_for_each_entry(cur, &objects, list) {
+ index = index_for_expected_id(expected, nr_ids, cur->id);
+ if (index < 0) {
+ pr_err("smo: ID not found: %ld\n", cur->id);
+ return -1;
+ }
+
+ if (expected[index] == -1) {
+ pr_err("smo: ID already encountered: %ld\n", cur->id);
+ return -1;
+ }
+ expected[index] = -1;
+ }
+ return 0;
+}
+
+/*
+ * smo_run_module_tests() - Runs unit tests from within the module
+ * @nr_objs: Number of objects to allocate.
+ * @keep: Free all but 1 in @keep objects.
+ *
+ * Allocates @nr_objects then iterates over the allocated objects
+ * freeing all but 1 out of every @keep objects i.e. for @keep==10
+ * keeps the first object then frees the next 9.
+ *
+ * Caller is responsible for ensuring that the cache has at most a
+ * single slab on the partial list without any objects in it. This is
+ * easy enough to ensure, just call this when the module is freshly
+ * loaded.
+ */
+static int smo_run_module_tests(int nr_objs, int keep)
+{
+ struct smo_slub_object *so;
+ struct smo_slub_object *cur, *tmp;
+ long i;
+
+ if (!list_empty(&objects)) {
+ pr_err("smo: test requires clean module state\n");
+ return -1;
+ }
+
+ /* Set sane parameters if no args passed in */
+ if (nr_objs == SMO_CMD_DEFAUT_ARG)
+ nr_objs = 1000;
+ if (keep == SMO_CMD_DEFAUT_ARG)
+ keep = 10;
+
+ pr_info("smo: test using nr_objs: %d keep: %d\n", nr_objs, keep);
+
+ /* Perhaps we got called like this 'test 1000' */
+ if (keep == 0) {
+ pr_err("Usage: test <nr_objs> <keep>\n");
+ return -1;
+ }
+
+ /* Test constructor */
+ so = kmem_cache_alloc(cachep, GFP_KERNEL);
+ if (!so) {
+ pr_err("smo: Failed to alloc object\n");
+ return -1;
+ }
+ if (so->id != -1) {
+ pr_err("smo: Initial state incorrect");
+ return -1;
+ }
+ kmem_cache_free(cachep, so);
+
+ /*
+ * Test that object migration is correctly implemented by module
+ *
+ * This gives us confidence that if new code correctly enables
+ * object migration (via correct implementation of migrate and
+ * isolate functions) then the slub allocator code that does
+ * object migration is correct.
+ */
+
+ for (i = 0; i < nr_objs; i++) {
+ so = kmem_cache_alloc(cachep, GFP_KERNEL);
+ if (!so) {
+ pr_err("smo: Failed to alloc object %ld of %d\n",
+ i, nr_objs);
+ return -1;
+ }
+ so->id = (long)i;
+ list_add_to_objects(so);
+ }
+
+ assert_have_objects(nr_objs, 1);
+
+ i = 0;
+ list_for_each_entry_safe(cur, tmp, &objects, list) {
+ if (i++ % keep == 0)
+ continue;
+
+ list_del(&cur->list);
+ kmem_cache_free(cachep, cur);
+ }
+
+ /* Verify shrink does nothing when migration is not enabled */
+ kmem_cache_shrink(cachep);
+ assert_have_objects(nr_objs, 1);
+
+ /* Now test shrink */
+ kmem_cache_setup_mobility(cachep, NULL, smo_cache_migrate);
+ kmem_cache_shrink(cachep);
+ /*
+ * Because of how migrate function deletes and adds objects to
+ * the objects list we have no way of knowing the order. We
+ * want to confirm that we have all the objects after shrink
+ * that we had before we did the shrink.
+ */
+ assert_have_objects(nr_objs, keep);
+
+ /* cleanup */
+ list_for_each_entry_safe(cur, tmp, &objects, list) {
+ list_del(&cur->list);
+ kmem_cache_free(cachep, cur);
+ }
+ kmem_cache_shrink(cachep); /* Remove empty slabs from partial list */
+
+ pr_info("smo: Module tests completed successfully\n");
+ return 0;
+}
+
+/*
+ * struct functions() - Map command to a function pointer.
+ */
+struct functions {
+ char *fn_name;
+ int (*fn_ptr)(int arg0, int arg1);
+} fn_tab[] = {
+ /*
+ * Because of the way we parse the function table no command
+ * may have another command as its prefix.
+ * i.e. this will break: 'foo' and 'foobar'
+ */
+ {"enable", smo_enable_cache_mobility},
+ {"alloc", smo_alloc_objects},
+ {"free", smo_free_object},
+ {"test", smo_run_module_tests},
+};
+
+#define FN_TAB_SIZE (sizeof(fn_tab) / sizeof(struct functions))
+
+/*
+ * parse_cmd_buf() - Gets command and arguments command string.
+ * @buf: Buffer containing the command string.
+ * @cmd: Out parameter, pointer to the command.
+ * @arg1: Out parameter, stores the first argument.
+ * @arg2: Out parameter, stores the second argument.
+ *
+ * Parses and tokenizes the input command buffer. Stores a pointer to the
+ * command (start of @buf) in @cmd. Stores the converted long values for
+ * argument 1 and 2 in the respective out parameters @arg1 and @arg2.
+ *
+ * Since arguments are optional, if they are not found the default values are
+ * returned. In order for the caller to differentiate defaults from arguments
+ * of the same value the number of arguments parsed is returned.
+ *
+ * Return: Number of arguments found.
+ */
+static int parse_cmd_buf(char *buf, char **cmd, long *arg1, long *arg2)
+{
+ int found;
+ char *ptr;
+ int ret;
+
+ *arg1 = SMO_CMD_DEFAUT_ARG;
+ *arg2 = SMO_CMD_DEFAUT_ARG;
+ found = 0;
+
+ /* Jump over the command, check if there are any args */
+ ptr = strsep(&buf, " ");
+ if (!ptr || !buf)
+ return found;
+
+ ptr = strsep(&buf, " ");
+ ret = kstrtol(ptr, 10, arg1);
+ if (ret < 0) {
+ pr_err("failed to convert arg, defaulting to %d. (%s)\n",
+ SMO_CMD_DEFAUT_ARG, ptr);
+ return found;
+ }
+ found++;
+ if (!buf) /* No second arg */
+ return found;
+
+ ptr = strsep(&buf, " ");
+ ret = kstrtol(ptr, 10, arg2);
+ if (ret < 0) {
+ pr_err("failed to convert arg, defaulting to %d. (%s)\n",
+ SMO_CMD_DEFAUT_ARG, ptr);
+ return found;
+ }
+ found++;
+
+ return found;
+}
+
+/*
+ * call_function() - Calls the function described by str.
+ * @str: '<cmd> [<arg>]'
+ *
+ * Does table lookup on <cmd>, calls appropriate function passing
+ * <arg> as a the argument. Optional arg defaults to 1.
+ */
+static void call_function(char *str)
+{
+ char *cmd;
+ long arg1 = 0;
+ long arg2 = 0;
+ int i;
+
+ if (!str)
+ return;
+
+ (void)parse_cmd_buf(str, &cmd, &arg1, &arg2);
+
+ for (i = 0; i < FN_TAB_SIZE; i++) {
+ char *fn_name = fn_tab[i].fn_name;
+
+ if (strcmp(fn_name, str) == 0) {
+ fn_tab[i].fn_ptr(arg1, arg2);
+ return; /* All done */
+ }
+ }
+
+ pr_err("failed to call function for cmd: %s\n", str);
+}
+
+/*
+ * smo_callfn_debugfs_write() - debugfs write function.
+ * @file: User file
+ * @user_buf: Userspace buffer
+ * @len: Length of the user space buffer
+ * @off: Offset within the file
+ *
+ * Used for triggering functions by writing command to debugfs file.
+ *
+ * echo '<cmd> <arg>' > /sys/kernel/debug/smo/callfn
+ *
+ * Return: Number of bytes copied if request succeeds,
+ * the corresponding error code otherwise.
+ */
+static ssize_t smo_callfn_debugfs_write(struct file *file,
+ const char __user *ubuf,
+ size_t len,
+ loff_t *off)
+{
+ char *kbuf;
+ int nbytes = 0;
+
+ if (*off != 0 || len == 0)
+ return -EINVAL;
+
+ kbuf = kzalloc(len, GFP_KERNEL);
+ if (!kbuf)
+ return -ENOMEM;
+
+ nbytes = strncpy_from_user(kbuf, ubuf, len);
+ if (nbytes < 0)
+ goto out;
+
+ if (kbuf[nbytes - 1] == '\n')
+ kbuf[nbytes - 1] = '\0';
+
+ call_function(kbuf); /* Tokenizes kbuf */
+out:
+ kfree(kbuf);
+ return nbytes;
+}
+
+const struct file_operations fops_callfn_debugfs = {
+ .owner = THIS_MODULE,
+ .write = smo_callfn_debugfs_write,
+};
+
+static int __init smo_debugfs_init(void)
+{
+ struct dentry *d;
+
+ smo_debugfs_root = debugfs_create_dir(SMO_DEBUGFS_DIR, NULL);
+ d = debugfs_create_file("callfn", 0200, smo_debugfs_root, NULL,
+ &fops_callfn_debugfs);
+ if (IS_ERR(d))
+ return PTR_ERR(d);
+
+ return 0;
+}
+
+static void __exit smo_debugfs_cleanup(void)
+{
+ debugfs_remove_recursive(smo_debugfs_root);
+}
+
+static int __init smo_cache_init(void)
+{
+ cachep = kmem_cache_create(SMO_CACHE_NAME,
+ sizeof(struct smo_slub_object),
+ 0, 0, smo_object_ctor);
+ if (!cachep)
+ return -1;
+
+ return 0;
+}
+
+static void __exit smo_cache_cleanup(void)
+{
+ struct smo_slub_object *cur, *tmp;
+
+ list_for_each_entry_safe(cur, tmp, &objects, list) {
+ list_del(&cur->list);
+ kmem_cache_free(cachep, cur);
+ }
+ kmem_cache_destroy(cachep);
+}
+
+static int __init smo_init(void)
+{
+ int ret;
+
+ ret = smo_cache_init();
+ if (ret) {
+ pr_err("smo: Failed to create cache\n");
+ return ret;
+ }
+ pr_info("smo: Created kmem_cache: %s\n", SMO_CACHE_NAME);
+
+ ret = smo_debugfs_init();
+ if (ret) {
+ pr_err("smo: Failed to init debugfs\n");
+ return ret;
+ }
+ pr_info("smo: Created debugfs directory: /sys/kernel/debugfs/%s\n",
+ SMO_DEBUGFS_DIR);
+
+ pr_info("smo: Test module loaded\n");
+ return 0;
+}
+module_init(smo_init);
+
+static void __exit smo_exit(void)
+{
+ smo_debugfs_cleanup();
+ smo_cache_cleanup();
+
+ pr_info("smo: Test module removed\n");
+}
+module_exit(smo_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Tobin C. Harding");
+MODULE_DESCRIPTION("SLUB Movable Objects test module.");
--
2.21.0
^ permalink raw reply related [flat|nested] 28+ messages in thread* [RFC PATCH v2 08/14] tools/testing/slab: Add object migration test suite
2019-04-03 4:21 [RFC PATCH v2 00/14] Slab Movable Objects (SMO) Tobin C. Harding
` (6 preceding siblings ...)
2019-04-03 4:21 ` [RFC PATCH v2 07/14] tools/testing/slab: Add object migration test module Tobin C. Harding
@ 2019-04-03 4:21 ` Tobin C. Harding
2019-04-03 4:21 ` [RFC PATCH v2 09/14] xarray: Implement migration function for objects Tobin C. Harding
` (5 subsequent siblings)
13 siblings, 0 replies; 28+ messages in thread
From: Tobin C. Harding @ 2019-04-03 4:21 UTC (permalink / raw)
To: Andrew Morton
Cc: Tobin C. Harding, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel
We just added a module that enables testing the SLUB allocators ability
to defrag/shrink caches via movable objects. Tests are better when they
are automated.
Add automated testing via a python script for SLUB movable objects.
Example output:
$ cd path/to/linux/tools/testing/slab
$ /slub_defrag.py
Please run script as root
$ sudo ./slub_defrag.py
<test are quiet, no output on success>
$ sudo ./slub_defrag.py --debug
Loading module ...
Slab cache smo_test created
Objects per slab: 20
Running sanity checks ...
Running module stress test (see dmesg for additional test output) ...
Removing module slub_defrag ...
Loading module ...
Slab cache smo_test created
Running test non-movable ...
testing slab 'smo_test' prior to enabling movable objects ...
verified non-movable slabs are NOT shrinkable
Running test movable ...
testing slab 'smo_test' after enabling movable objects ...
verified movable slabs are shrinkable
Removing module slub_defrag ...
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
---
tools/testing/slab/slub_defrag.c | 1 +
tools/testing/slab/slub_defrag.py | 451 ++++++++++++++++++++++++++++++
2 files changed, 452 insertions(+)
create mode 100755 tools/testing/slab/slub_defrag.py
diff --git a/tools/testing/slab/slub_defrag.c b/tools/testing/slab/slub_defrag.c
index 4a5c24394b96..8332e69ee868 100644
--- a/tools/testing/slab/slub_defrag.c
+++ b/tools/testing/slab/slub_defrag.c
@@ -337,6 +337,7 @@ static int smo_run_module_tests(int nr_objs, int keep)
/*
* struct functions() - Map command to a function pointer.
+ * If you update this please update the documentation in slub_defrag.py
*/
struct functions {
char *fn_name;
diff --git a/tools/testing/slab/slub_defrag.py b/tools/testing/slab/slub_defrag.py
new file mode 100755
index 000000000000..41747c0db39b
--- /dev/null
+++ b/tools/testing/slab/slub_defrag.py
@@ -0,0 +1,451 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import subprocess
+import sys
+from os import path
+
+# SLUB Movable Objects test suite.
+#
+# Requirements:
+# - CONFIG_SLUB=y
+# - CONFIG_SLUB_DEBUG=y
+# - The slub_defrag module in this directory.
+
+# Test SMO using a kernel module that enables triggering arbitrary
+# kernel code from userspace via a debugfs file.
+#
+# Module code is in ./slub_defrag.c, basically the functionality is as
+# follows:
+#
+# - Creates debugfs file /sys/kernel/debugfs/smo/callfn
+# - Writes to 'callfn' are parsed as a command string and the function
+# associated with command is called.
+# - Defines 4 commands (all commands operate on smo_test cache):
+# - 'test': Runs module stress tests.
+# - 'alloc N': Allocates N slub objects
+# - 'free N POS': Frees N objects starting at POS (see below)
+# - 'enable': Enables SLUB Movable Objects
+#
+# The module maintains a list of allocated objects. Allocation adds
+# objects to the tail of the list. Free'ing frees from the head of the
+# list. This has the effect of creating free slots in the slab. For
+# finer grained control over where in the cache slots are free'd POS
+# (position) argument may be used.
+
+# The main() function is reasonably readable; the test suite does the
+# following:
+#
+# 1. Runs the module stress tests.
+# 2. Tests the cache without movable objects enabled.
+# - Creates multiple partial slabs as explained above.
+# - Verifies that partial slabs are _not_ removed by shrink (see below).
+# 3. Tests the cache with movable objects enabled.
+# - Creates multiple partial slabs as explained above.
+# - Verifies that partial slabs _are_ removed by shrink (see below).
+
+# The sysfs file /sys/kernel/slab/<cache>/shrink enables calling the
+# function kmem_cache_shrink() (see mm/slab_common.c and mm/slub.cc).
+# Shrinking a cache attempts to consolidate all partial slabs by moving
+# objects if object migration is enable for the cache, otherwise
+# shrinking a cache simply re-orders the partial list so as most densely
+# populated slab are at the head of the list.
+
+# Enable/disable debugging output (also enabled via -d | --debug).
+debug = False
+
+# Used in debug messages and when running `insmod`.
+MODULE_NAME = "slub_defrag"
+
+# Slab cache created by the test module.
+CACHE_NAME = "smo_test"
+
+# Set by get_slab_config()
+objects_per_slab = 0
+pages_per_slab = 0
+debugfs_mounted = False # Set to true if we mount debugfs.
+
+
+def eprint(*args, **kwargs):
+ print(*args, file=sys.stderr, **kwargs)
+
+
+def dprint(*args, **kwargs):
+ if debug:
+ print(*args, file=sys.stderr, **kwargs)
+
+
+def run_shell(cmd):
+ return subprocess.call([cmd], shell=True)
+
+
+def run_shell_get_stdout(cmd):
+ return subprocess.check_output([cmd], shell=True)
+
+
+def assert_root():
+ user = run_shell_get_stdout('whoami')
+ if user != b'root\n':
+ eprint("Please run script as root")
+ sys.exit(1)
+
+
+def mount_debugfs():
+ mounted = False
+
+ # Check if debugfs is mounted at a known mount point.
+ ret = run_shell('mount -l | grep /sys/kernel/debug > /dev/null 2>&1')
+ if ret != 0:
+ run_shell('mount -t debugfs none /sys/kernel/debug/')
+ mounted = True
+ dprint("Mounted debugfs on /sys/kernel/debug")
+
+ return mounted
+
+
+def umount_debugfs():
+ dprint("Un-mounting debugfs")
+ run_shell('umount /sys/kernel/debug')
+
+
+def load_module():
+ """Loads the test module.
+
+ We need a clean slab state to start with so module must
+ be loaded by the test suite.
+ """
+ ret = run_shell('lsmod | grep %s > /dev/null' % MODULE_NAME)
+ if ret == 0:
+ eprint("Please unload slub_defrag module before running test suite")
+ return -1
+
+ dprint('Loading module ...')
+ ret = run_shell('insmod %s.ko' % MODULE_NAME)
+ if ret != 0: # ret==1 on error
+ return -1
+
+ dprint("Slab cache %s created" % CACHE_NAME)
+ return 0
+
+
+def unload_module():
+ ret = run_shell('lsmod | grep %s > /dev/null' % MODULE_NAME)
+ if ret == 0:
+ dprint('Removing module %s ...' % MODULE_NAME)
+ run_shell('rmmod %s > /dev/null 2>&1' % MODULE_NAME)
+
+
+def get_sysfs_value(filename):
+ """
+ Parse slab sysfs files (single line: '20 N0=20')
+ """
+ path = '/sys/kernel/slab/smo_test/%s' % filename
+ f = open(path, "r")
+ s = f.readline()
+ tokens = s.split(" ")
+
+ return int(tokens[0])
+
+
+def get_nr_objects_active():
+ return get_sysfs_value('objects')
+
+
+def get_nr_objects_total():
+ return get_sysfs_value('total_objects')
+
+
+def get_nr_slabs_total():
+ return get_sysfs_value('slabs')
+
+
+def get_nr_slabs_partial():
+ return get_sysfs_value('partial')
+
+
+def get_nr_slabs_full():
+ return get_nr_slabs_total() - get_nr_slabs_partial()
+
+
+def get_slab_config():
+ """Get relevant information from sysfs."""
+ global objects_per_slab
+
+ objects_per_slab = get_sysfs_value('objs_per_slab')
+ if objects_per_slab < 0:
+ return -1
+
+ dprint("Objects per slab: %d" % objects_per_slab)
+ return 0
+
+
+def verify_state(nr_objects_active, nr_objects_total,
+ nr_slabs_partial, nr_slabs_full, nr_slabs_total, msg=''):
+ err = 0
+ got_nr_objects_active = get_nr_objects_active()
+ got_nr_objects_total = get_nr_objects_total()
+ got_nr_slabs_partial = get_nr_slabs_partial()
+ got_nr_slabs_full = get_nr_slabs_full()
+ got_nr_slabs_total = get_nr_slabs_total()
+
+ if got_nr_objects_active != nr_objects_active:
+ err = -1
+
+ if got_nr_objects_total != nr_objects_total:
+ err = -2
+
+ if got_nr_slabs_partial != nr_slabs_partial:
+ err = -3
+
+ if got_nr_slabs_full != nr_slabs_full:
+ err = -4
+
+ if got_nr_slabs_total != nr_slabs_total:
+ err = -5
+
+ if err != 0:
+ dprint("Verify state: %s" % msg)
+ dprint(" what\t\t\twant\tgot")
+ dprint("-----------------------------------------")
+ dprint(" %s\t%d\t%d" % ('nr_objects_active', nr_objects_active, got_nr_objects_active))
+ dprint(" %s\t%d\t%d" % ('nr_objects_total', nr_objects_total, got_nr_objects_total))
+ dprint(" %s\t%d\t%d" % ('nr_slabs_partial', nr_slabs_partial, got_nr_slabs_partial))
+ dprint(" %s\t\t%d\t%d" % ('nr_slabs_full', nr_slabs_full, got_nr_slabs_full))
+ dprint(" %s\t%d\t%d\n" % ('nr_slabs_total', nr_slabs_total, got_nr_slabs_total))
+
+ return err
+
+
+def exec_via_sysfs(command):
+ ret = run_shell('echo %s > /sys/kernel/debug/smo/callfn' % command)
+ if ret != 0:
+ eprint("Failed to echo command to sysfs: %s" % command)
+
+ return ret
+
+
+def enable_movable_objects():
+ return exec_via_sysfs('enable')
+
+
+def alloc(n):
+ exec_via_sysfs("alloc %d" % n)
+
+
+def free(n, pos = 0):
+ exec_via_sysfs('free %d %d' % (n, pos))
+
+
+def shrink():
+ ret = run_shell('slabinfo smo_test -s')
+ if ret != 0:
+ eprint("Failed to execute slabinfo -s")
+
+
+def sanity_checks():
+ # Verify everything is 0 to start with.
+ return verify_state(0, 0, 0, 0, 0, "sanity check")
+
+
+def test_non_movable():
+ one_over = objects_per_slab + 1
+
+ dprint("testing slab 'smo_test' prior to enabling movable objects ...")
+
+ alloc(one_over)
+
+ objects_active = one_over
+ objects_total = objects_per_slab * 2
+ slabs_partial = 1
+ slabs_full = 1
+ slabs_total = 2
+ ret = verify_state(objects_active, objects_total,
+ slabs_partial, slabs_full, slabs_total,
+ "non-movable: initial allocation")
+ if ret != 0:
+ eprint("test_non_movable: failed to verify initial state")
+ return -1
+
+ # Free object from first slot of first slab.
+ free(1)
+ objects_active = one_over - 1
+ objects_total = objects_per_slab * 2
+ slabs_partial = 2
+ slabs_full = 0
+ slabs_total = 2
+ ret = verify_state(objects_active, objects_total,
+ slabs_partial, slabs_full, slabs_total,
+ "non-movable: after free")
+ if ret != 0:
+ eprint("test_non_movable: failed to verify after free")
+ return -1
+
+ # Non-movable cache, shrink should have no effect.
+ shrink()
+ ret = verify_state(objects_active, objects_total,
+ slabs_partial, slabs_full, slabs_total,
+ "non-movable: after shrink")
+ if ret != 0:
+ eprint("test_non_movable: failed to verify after shrink")
+ return -1
+
+ # Cleanup
+ free(objects_per_slab)
+ shrink()
+
+ dprint("verified non-movable slabs are NOT shrinkable")
+ return 0
+
+
+def test_movable():
+ one_over = objects_per_slab + 1
+
+ dprint("testing slab 'smo_test' after enabling movable objects ...")
+
+ alloc(one_over)
+
+ objects_active = one_over
+ objects_total = objects_per_slab * 2
+ slabs_partial = 1
+ slabs_full = 1
+ slabs_total = 2
+ ret = verify_state(objects_active, objects_total,
+ slabs_partial, slabs_full, slabs_total,
+ "movable: initial allocation")
+ if ret != 0:
+ eprint("test_movable: failed to verify initial state")
+ return -1
+
+ # Free object from first slot of first slab.
+ free(1)
+ objects_active = one_over - 1
+ objects_total = objects_per_slab * 2
+ slabs_partial = 2
+ slabs_full = 0
+ slabs_total = 2
+ ret = verify_state(objects_active, objects_total,
+ slabs_partial, slabs_full, slabs_total,
+ "movable: after free")
+ if ret != 0:
+ eprint("test_movable: failed to verify after free")
+ return -1
+
+ # movable cache, shrink should move objects and free slab.
+ shrink()
+ objects_active = one_over - 1
+ objects_total = objects_per_slab * 1
+ slabs_partial = 0
+ slabs_full = 1
+ slabs_total = 1
+ ret = verify_state(objects_active, objects_total,
+ slabs_partial, slabs_full, slabs_total,
+ "movable: after shrink")
+ if ret != 0:
+ eprint("test_movable: failed to verify after shrink")
+ return -1
+
+ # Cleanup
+ free(objects_per_slab)
+ shrink()
+
+ dprint("verified movable slabs are shrinkable")
+ return 0
+
+
+def dprint_start_test(test):
+ dprint("Running %s ..." % test)
+
+
+def dprint_done():
+ dprint("")
+
+
+def run_test(fn, desc):
+ dprint_start_test(desc)
+ ret = fn()
+ if ret < 0:
+ fail_test(desc)
+ dprint_done()
+
+
+# Load and unload the module for this test to ensure clean state.
+def run_module_stress_test():
+ dprint("Running module stress test (see dmesg for additional test output) ...")
+
+ unload_module()
+ ret = load_module()
+ if ret < 0:
+ cleanup_and_exit(ret)
+
+ exec_via_sysfs("test");
+
+ unload_module()
+
+ dprint()
+
+
+def fail_test(msg):
+ eprint("\nFAIL: test failed: '%s' ... aborting\n" % msg)
+ cleanup_and_exit(1)
+
+
+def display_help():
+ print("Usage: %s [OPTIONS]\n" % path.basename(sys.argv[0]))
+ print("\tRuns defrag test suite (a.k.a. SLUB Movable Objects)\n")
+ print("OPTIONS:")
+ print("\t-d | --debug Enable verbose debug output")
+ print("\t-h | --help Print this help and exit")
+
+
+def cleanup_and_exit(return_code):
+ global debugfs_mounted
+
+ if debugfs_mounted == True:
+ umount_debugfs()
+
+ unload_module()
+
+ sys.exit(return_code)
+
+
+def main():
+ global debug
+
+ if len(sys.argv) > 1:
+ if sys.argv[1] == '-h' or sys.argv[1] == '--help':
+ display_help()
+ sys.exit(0)
+
+ if sys.argv[1] == '-d' or sys.argv[1] == '--debug':
+ debug = True
+
+ assert_root()
+
+ # Use cleanup_and_exit() instead of sys.exit() after mounting debugfs.
+ debugfs_mounted = mount_debugfs()
+
+ # Loads and unloads the module.
+ run_module_stress_test()
+
+ ret = load_module()
+ if (ret < 0):
+ cleanup_and_exit(ret)
+
+ ret = get_slab_config()
+ if (ret != 0):
+ fail_test("get slab config details")
+
+ run_test(sanity_checks, "sanity checks")
+
+ run_test(test_non_movable, "test non-movable")
+
+ ret = enable_movable_objects()
+ if (ret != 0):
+ fail_test("enable movable objects")
+
+ run_test(test_movable, "test movable")
+
+ cleanup_and_exit(0)
+
+if __name__== "__main__":
+ main()
--
2.21.0
^ permalink raw reply related [flat|nested] 28+ messages in thread* [RFC PATCH v2 09/14] xarray: Implement migration function for objects
2019-04-03 4:21 [RFC PATCH v2 00/14] Slab Movable Objects (SMO) Tobin C. Harding
` (7 preceding siblings ...)
2019-04-03 4:21 ` [RFC PATCH v2 08/14] tools/testing/slab: Add object migration test suite Tobin C. Harding
@ 2019-04-03 4:21 ` Tobin C. Harding
2019-04-03 17:23 ` Matthew Wilcox
2019-04-03 4:21 ` [RFC PATCH v2 10/14] tools/testing/slab: Add XArray movable objects tests Tobin C. Harding
` (4 subsequent siblings)
13 siblings, 1 reply; 28+ messages in thread
From: Tobin C. Harding @ 2019-04-03 4:21 UTC (permalink / raw)
To: Andrew Morton
Cc: Tobin C. Harding, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel
Implement functions to migrate objects. This is based on
initial code by Matthew Wilcox and was modified to work with
slab object migration.
Cc: Matthew Wilcox <willy@infradead.org>
Co-developed-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
---
lib/radix-tree.c | 13 +++++++++++++
lib/xarray.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 59 insertions(+)
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 14d51548bea6..9412c2853726 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -1613,6 +1613,17 @@ static int radix_tree_cpu_dead(unsigned int cpu)
return 0;
}
+extern void xa_object_migrate(void *tree_node, int numa_node);
+
+static void radix_tree_migrate(struct kmem_cache *s, void **objects, int nr,
+ int node, void *private)
+{
+ int i;
+
+ for (i = 0; i < nr; i++)
+ xa_object_migrate(objects[i], node);
+}
+
void __init radix_tree_init(void)
{
int ret;
@@ -1627,4 +1638,6 @@ void __init radix_tree_init(void)
ret = cpuhp_setup_state_nocalls(CPUHP_RADIX_DEAD, "lib/radix:dead",
NULL, radix_tree_cpu_dead);
WARN_ON(ret < 0);
+ kmem_cache_setup_mobility(radix_tree_node_cachep, NULL,
+ radix_tree_migrate);
}
diff --git a/lib/xarray.c b/lib/xarray.c
index 6be3acbb861f..6d2657f2e4cb 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1971,6 +1971,52 @@ void xa_destroy(struct xarray *xa)
}
EXPORT_SYMBOL(xa_destroy);
+void xa_object_migrate(struct xa_node *node, int numa_node)
+{
+ struct xarray *xa = READ_ONCE(node->array);
+ void __rcu **slot;
+ struct xa_node *new_node;
+ int i;
+
+ /* Freed or not yet in tree then skip */
+ if (!xa || xa == XA_RCU_FREE)
+ return;
+
+ new_node = kmem_cache_alloc_node(radix_tree_node_cachep,
+ GFP_KERNEL, numa_node);
+ if (!new_node)
+ return;
+
+ xa_lock_irq(xa);
+
+ /* Check again..... */
+ if (xa != node->array || !list_empty(&node->private_list)) {
+ node = new_node;
+ goto unlock;
+ }
+
+ memcpy(new_node, node, sizeof(struct xa_node));
+
+ /* Move pointers to new node */
+ INIT_LIST_HEAD(&new_node->private_list);
+ for (i = 0; i < XA_CHUNK_SIZE; i++) {
+ void *x = xa_entry_locked(xa, new_node, i);
+
+ if (xa_is_node(x))
+ rcu_assign_pointer(xa_to_node(x)->parent, new_node);
+ }
+ if (!new_node->parent)
+ slot = &xa->xa_head;
+ else
+ slot = &xa_parent_locked(xa, new_node)->slots[new_node->offset];
+ rcu_assign_pointer(*slot, xa_mk_node(new_node));
+
+unlock:
+ xa_unlock_irq(xa);
+ xa_node_free(node);
+ rcu_barrier();
+}
+
#ifdef XA_DEBUG
void xa_dump_node(const struct xa_node *node)
{
--
2.21.0
^ permalink raw reply related [flat|nested] 28+ messages in thread* Re: [RFC PATCH v2 09/14] xarray: Implement migration function for objects
2019-04-03 4:21 ` [RFC PATCH v2 09/14] xarray: Implement migration function for objects Tobin C. Harding
@ 2019-04-03 17:23 ` Matthew Wilcox
2019-04-03 21:19 ` Tobin C. Harding
0 siblings, 1 reply; 28+ messages in thread
From: Matthew Wilcox @ 2019-04-03 17:23 UTC (permalink / raw)
To: Tobin C. Harding
Cc: Andrew Morton, Roman Gushchin, Alexander Viro, Christoph Hellwig,
Pekka Enberg, David Rientjes, Joonsoo Kim, Christopher Lameter,
Miklos Szeredi, Andreas Dilger, Waiman Long, Tycho Andersen,
Theodore Ts'o, Andi Kleen, David Chinner, Nick Piggin,
Rik van Riel, Hugh Dickins, linux-mm, linux-fsdevel,
linux-kernel
On Wed, Apr 03, 2019 at 03:21:22PM +1100, Tobin C. Harding wrote:
> +void xa_object_migrate(struct xa_node *node, int numa_node)
> +{
> + struct xarray *xa = READ_ONCE(node->array);
> + void __rcu **slot;
> + struct xa_node *new_node;
> + int i;
> +
> + /* Freed or not yet in tree then skip */
> + if (!xa || xa == XA_RCU_FREE)
> + return;
> +
> + new_node = kmem_cache_alloc_node(radix_tree_node_cachep,
> + GFP_KERNEL, numa_node);
> + if (!new_node)
> + return;
> +
> + xa_lock_irq(xa);
> +
> + /* Check again..... */
> + if (xa != node->array || !list_empty(&node->private_list)) {
> + node = new_node;
> + goto unlock;
> + }
> +
> + memcpy(new_node, node, sizeof(struct xa_node));
> +
> + /* Move pointers to new node */
> + INIT_LIST_HEAD(&new_node->private_list);
Surely we can do something more clever, like ...
if (xa != node->array) {
...
if (list_empty(&node->private_list))
INIT_LIST_HEAD(&new_node->private_list);
else
list_replace(&node->private_list, &new_node->private_list);
BTW, the raidx tree nodes / xa_nodes share the same slab cache; we need
to finish converting all radix tree & IDR users to the XArray before
this series can go in.
^ permalink raw reply [flat|nested] 28+ messages in thread* Re: [RFC PATCH v2 09/14] xarray: Implement migration function for objects
2019-04-03 17:23 ` Matthew Wilcox
@ 2019-04-03 21:19 ` Tobin C. Harding
0 siblings, 0 replies; 28+ messages in thread
From: Tobin C. Harding @ 2019-04-03 21:19 UTC (permalink / raw)
To: Matthew Wilcox
Cc: Tobin C. Harding, Andrew Morton, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Miklos Szeredi, Andreas Dilger, Waiman Long,
Tycho Andersen, Theodore Ts'o, Andi Kleen, David Chinner,
Nick Piggin, Rik van Riel, Hugh Dickins, linux-mm, linux-fsdevel,
linux-kernel
On Wed, Apr 03, 2019 at 10:23:26AM -0700, Matthew Wilcox wrote:
> On Wed, Apr 03, 2019 at 03:21:22PM +1100, Tobin C. Harding wrote:
> > +void xa_object_migrate(struct xa_node *node, int numa_node)
> > +{
> > + struct xarray *xa = READ_ONCE(node->array);
> > + void __rcu **slot;
> > + struct xa_node *new_node;
> > + int i;
> > +
> > + /* Freed or not yet in tree then skip */
> > + if (!xa || xa == XA_RCU_FREE)
> > + return;
> > +
> > + new_node = kmem_cache_alloc_node(radix_tree_node_cachep,
> > + GFP_KERNEL, numa_node);
> > + if (!new_node)
> > + return;
> > +
> > + xa_lock_irq(xa);
> > +
> > + /* Check again..... */
> > + if (xa != node->array || !list_empty(&node->private_list)) {
> > + node = new_node;
> > + goto unlock;
> > + }
> > +
> > + memcpy(new_node, node, sizeof(struct xa_node));
> > +
> > + /* Move pointers to new node */
> > + INIT_LIST_HEAD(&new_node->private_list);
>
> Surely we can do something more clever, like ...
>
> if (xa != node->array) {
> ...
> if (list_empty(&node->private_list))
> INIT_LIST_HEAD(&new_node->private_list);
> else
> list_replace(&node->private_list, &new_node->private_list);
Oh nice, thanks! I'll roll this into the next version.
> BTW, the raidx tree nodes / xa_nodes share the same slab cache; we need
> to finish converting all radix tree & IDR users to the XArray before
> this series can go in.
Ok, I'll add this comment to the commit log for this patch on the next
version so we don't forget. FTR complete conversion to the XArray is
your goal isn't it (on the way to the Maple tree)?
thanks,
Tobin.
^ permalink raw reply [flat|nested] 28+ messages in thread
* [RFC PATCH v2 10/14] tools/testing/slab: Add XArray movable objects tests
2019-04-03 4:21 [RFC PATCH v2 00/14] Slab Movable Objects (SMO) Tobin C. Harding
` (8 preceding siblings ...)
2019-04-03 4:21 ` [RFC PATCH v2 09/14] xarray: Implement migration function for objects Tobin C. Harding
@ 2019-04-03 4:21 ` Tobin C. Harding
2019-04-03 4:21 ` [RFC PATCH v2 11/14] slub: Enable moving objects to/from specific nodes Tobin C. Harding
` (3 subsequent siblings)
13 siblings, 0 replies; 28+ messages in thread
From: Tobin C. Harding @ 2019-04-03 4:21 UTC (permalink / raw)
To: Andrew Morton
Cc: Tobin C. Harding, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel
We just implemented movable objects for the XArray. Let's test it
intree.
Add test module for the XArray's movable objects implementation.
Functionality of the XArray Slab Movable Object implementation can
usually be seen by simply by using `slabinfo` on a running machine since
the radix tree is typically in use on a running machine and will have
partial slabs. For repeated testing we can use the test module to run
to simulate a workload on the XArray then use `slabinfo` to test object
migration is functioning.
If testing on freshly spun up VM (low radix tree workload) it may be
necessary to load/unload the module a number of times to create partial
slabs.
Example test session
--------------------
Relevant /proc/slabinfo column headers:
name <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab>
Prior to testing slabinfo report for radix_tree_node:
# slabinfo radix_tree_node --report
Slabcache: radix_tree_node Aliases: 0 Order : 2 Objects: 8352
** Reclaim accounting active
** Defragmentation at 30%
Sizes (bytes) Slabs Debug Memory
------------------------------------------------------------------------
Object : 576 Total : 497 Sanity Checks : On Total: 8142848
SlabObj: 912 Full : 473 Redzoning : On Used : 4810752
SlabSiz: 16384 Partial: 24 Poisoning : On Loss : 3332096
Loss : 336 CpuSlab: 0 Tracking : On Lalig: 2806272
Align : 8 Objects: 17 Tracing : Off Lpadd: 437360
Here you can see the kernel was built with Slab Movable Objects enabled
for the XArray (XArray uses the radix tree below the surface).
After inserting the test module (note we have triggered allocation of a
number of radix tree nodes increasing the object count but decreasing the
number of partial slabs):
# slabinfo radix_tree_node --report
Slabcache: radix_tree_node Aliases: 0 Order : 2 Objects: 8442
** Reclaim accounting active
** Defragmentation at 30%
Sizes (bytes) Slabs Debug Memory
------------------------------------------------------------------------
Object : 576 Total : 499 Sanity Checks : On Total: 8175616
SlabObj: 912 Full : 484 Redzoning : On Used : 4862592
SlabSiz: 16384 Partial: 15 Poisoning : On Loss : 3313024
Loss : 336 CpuSlab: 0 Tracking : On Lalig: 2836512
Align : 8 Objects: 17 Tracing : Off Lpadd: 439120
Now we can shrink the radix_tree_node cache:
# slabinfo radix_tree_node --shrink
# slabinfo radix_tree_node --report
Slabcache: radix_tree_node Aliases: 0 Order : 2 Objects: 8515
** Reclaim accounting active
** Defragmentation at 30%
Sizes (bytes) Slabs Debug Memory
------------------------------------------------------------------------
Object : 576 Total : 501 Sanity Checks : On Total: 8208384
SlabObj: 912 Full : 500 Redzoning : On Used : 4904640
SlabSiz: 16384 Partial: 1 Poisoning : On Loss : 3303744
Loss : 336 CpuSlab: 0 Tracking : On Lalig: 2861040
Align : 8 Objects: 17 Tracing : Off Lpadd: 440880
Note the single remaining partial slab.
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
---
tools/testing/slab/Makefile | 2 +-
tools/testing/slab/slub_defrag_xarray.c | 211 ++++++++++++++++++++++++
2 files changed, 212 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/slab/slub_defrag_xarray.c
diff --git a/tools/testing/slab/Makefile b/tools/testing/slab/Makefile
index 440c2e3e356f..44c18d9a4d52 100644
--- a/tools/testing/slab/Makefile
+++ b/tools/testing/slab/Makefile
@@ -1,4 +1,4 @@
-obj-m += slub_defrag.o
+obj-m += slub_defrag.o slub_defrag_xarray.o
KTREE=../../..
diff --git a/tools/testing/slab/slub_defrag_xarray.c b/tools/testing/slab/slub_defrag_xarray.c
new file mode 100644
index 000000000000..41143f73256c
--- /dev/null
+++ b/tools/testing/slab/slub_defrag_xarray.c
@@ -0,0 +1,211 @@
+// SPDX-License-Identifier: GPL-2.0+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/uaccess.h>
+#include <linux/list.h>
+#include <linux/gfp.h>
+#include <linux/xarray.h>
+
+#define SMOX_CACHE_NAME "smox_test"
+static struct kmem_cache *cachep;
+
+/*
+ * Declare XArrays globally so we can clean them up on module unload.
+ */
+
+/* Used by test_smo_xarray()*/
+DEFINE_XARRAY(things);
+
+/* Thing to store pointers to in the XArray */
+struct smox_thing {
+ long id;
+};
+
+/* It's up to the caller to ensure id is unique */
+static struct smox_thing *alloc_thing(int id)
+{
+ struct smox_thing *thing;
+
+ thing = kmem_cache_alloc(cachep, GFP_KERNEL);
+ if (!thing)
+ return ERR_PTR(-ENOMEM);
+
+ thing->id = id;
+ return thing;
+}
+
+/**
+ * smox_object_ctor() - SMO object constructor function.
+ * @ptr: Pointer to memory where the object should be constructed.
+ */
+void smox_object_ctor(void *ptr)
+{
+ struct smox_thing *thing = ptr;
+
+ thing->id = -1;
+}
+
+/**
+ * smox_cache_migrate() - kmem_cache migrate function.
+ * @cp: kmem_cache pointer.
+ * @objs: Array of pointers to objects to migrate.
+ * @size: Number of objects in @objs.
+ * @node: NUMA node where the object should be allocated.
+ * @private: Pointer returned by kmem_cache_isolate_func().
+ */
+void smox_cache_migrate(struct kmem_cache *cp, void **objs, int size,
+ int node, void *private)
+{
+ struct smox_thing **ptrs = (struct smox_thing **)objs;
+ struct smox_thing *old, *new;
+ struct smox_thing *thing;
+ unsigned long index;
+ void *entry;
+ int i;
+
+ for (i = 0; i < size; i++) {
+ old = ptrs[i];
+
+ new = kmem_cache_alloc(cachep, GFP_KERNEL);
+ if (!new) {
+ pr_debug("kmem_cache_alloc failed\n");
+ return;
+ }
+
+ new->id = old->id;
+
+ /* Update reference the brain dead way */
+ xa_for_each(&things, index, thing) {
+ if (thing == old) {
+ entry = xa_store(&things, index, new, GFP_KERNEL);
+ if (entry != old) {
+ pr_err("failed to exchange new/old\n");
+ return;
+ }
+ }
+ }
+ kmem_cache_free(cachep, old);
+ }
+}
+
+/*
+ * test_smo_xarray() - Run some tests using an XArray.
+ */
+static int test_smo_xarray(void)
+{
+ const int keep = 6; /* Free 5 out of 6 items */
+ const int nr_items = 10000;
+ struct smox_thing *thing;
+ unsigned long index;
+ void *entry;
+ int expected;
+ int i;
+
+ /*
+ * Populate XArray, this adds to the radix_tree_node cache as
+ * well as the smox_test cache.
+ */
+ for (i = 0; i < nr_items; i++) {
+ thing = alloc_thing(i);
+ entry = xa_store(&things, i, thing, GFP_KERNEL);
+ if (xa_is_err(entry)) {
+ pr_err("smox: failed to allocate entry: %d\n", i);
+ return -ENOMEM;
+ }
+ }
+
+ /* Now free items, putting holes in both caches. */
+ for (i = 0; i < nr_items; i++) {
+ if (i % keep == 0)
+ continue;
+
+ thing = xa_erase(&things, i);
+ if (xa_is_err(thing))
+ pr_err("smox: error erasing entry: %d\n", i);
+ kmem_cache_free(cachep, thing);
+ }
+
+ expected = 0;
+ xa_for_each(&things, index, thing) {
+ if (thing->id != expected || index != expected) {
+ pr_err("smox: error; got %ld want %d at %ld\n",
+ thing->id, expected, index);
+ return -1;
+ }
+ expected += keep;
+ }
+
+ /*
+ * Leave caches sparsely allocated. Shrink caches manually with:
+ *
+ * slabinfo radix_tree_node --shrink
+ * slabinfo smox_test --shrink
+ */
+
+ return 0;
+}
+
+static int __init smox_cache_init(void)
+{
+ cachep = kmem_cache_create(SMOX_CACHE_NAME,
+ sizeof(struct smox_thing),
+ 0, 0, smox_object_ctor);
+ if (!cachep)
+ return -1;
+
+ return 0;
+}
+
+static void __exit smox_cache_cleanup(void)
+{
+ struct smox_thing *thing;
+ unsigned long i;
+
+ xa_for_each(&things, i, thing) {
+ kmem_cache_free(cachep, thing);
+ }
+ xa_destroy(&things);
+ kmem_cache_destroy(cachep);
+}
+
+static int __init smox_init(void)
+{
+ int ret;
+
+ ret = smox_cache_init();
+ if (ret) {
+ pr_err("smo_xarray: failed to create cache\n");
+ return ret;
+ }
+ pr_info("smo_xarray: created kmem_cache: %s\n", SMOX_CACHE_NAME);
+
+ kmem_cache_setup_mobility(cachep, NULL, smox_cache_migrate);
+ pr_info("smo_xarray: kmem_cache %s defrag enabled\n", SMOX_CACHE_NAME);
+
+ /*
+ * Running this test consumes memory unless you shrink the
+ * radix_tree_node cache manually with `slabinfo`.
+ */
+ ret = test_smo_xarray();
+ if (ret)
+ pr_warn("test_smo_xarray failed: %d\n", ret);
+
+ pr_info("smo_xarray: module loaded successfully\n");
+ return 0;
+}
+module_init(smox_init);
+
+static void __exit smox_exit(void)
+{
+ smox_cache_cleanup();
+
+ pr_info("smo_xarray: module removed\n");
+}
+module_exit(smox_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Tobin C. Harding");
+MODULE_DESCRIPTION("SMO XArray test module.");
--
2.21.0
^ permalink raw reply related [flat|nested] 28+ messages in thread* [RFC PATCH v2 11/14] slub: Enable moving objects to/from specific nodes
2019-04-03 4:21 [RFC PATCH v2 00/14] Slab Movable Objects (SMO) Tobin C. Harding
` (9 preceding siblings ...)
2019-04-03 4:21 ` [RFC PATCH v2 10/14] tools/testing/slab: Add XArray movable objects tests Tobin C. Harding
@ 2019-04-03 4:21 ` Tobin C. Harding
2019-04-03 4:21 ` [RFC PATCH v2 12/14] slub: Enable balancing slabs across nodes Tobin C. Harding
` (2 subsequent siblings)
13 siblings, 0 replies; 28+ messages in thread
From: Tobin C. Harding @ 2019-04-03 4:21 UTC (permalink / raw)
To: Andrew Morton
Cc: Tobin C. Harding, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel
We have just implemented Slab Movable Objects (object migration).
Currently object migration is used to defrag a cache. On NUMA systems
it would be nice to be able to control the source and destination nodes
when moving objects.
Add CONFIG_SMO_NODE to guard this feature. CONFIG_SMO_NODE depends on
CONFIG_SLUB_DEBUG because we use the full list. Leave it like this for
the RFC because the patch will be less cluttered to review, separate
full list out of CONFIG_DEBUG before doing a PATCH version.
Implement moving all objects (including those in full slabs) to a
specific node. Expose this functionality to userspace via a sysfs entry.
Add sysfs entry:
/sysfs/kernel/slab/<cache>/move
With this users get access to the following functionality:
- Move all objects to specified node.
echo "N1" > move
- Move all objects from specified node to other specified
node (from N1 -> to N2):
echo "N1 N2" > move
This also enables shrinking slabs on a specific node:
echo "N1 N1" > move
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
---
mm/Kconfig | 7 ++
mm/slub.c | 249 +++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 256 insertions(+)
diff --git a/mm/Kconfig b/mm/Kconfig
index 25c71eb8a7db..47040d939f3b 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -258,6 +258,13 @@ config ARCH_ENABLE_HUGEPAGE_MIGRATION
config ARCH_ENABLE_THP_MIGRATION
bool
+config SMO_NODE
+ bool "Enable per node control of Slab Movable Objects"
+ depends on SLUB && SYSFS
+ select SLUB_DEBUG
+ help
+ On NUMA systems enable moving objects to and from a specified node.
+
config PHYS_ADDR_T_64BIT
def_bool 64BIT
diff --git a/mm/slub.c b/mm/slub.c
index e601c804ed79..e4f3dde443f5 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4345,6 +4345,106 @@ static void move_slab_page(struct page *page, void *scratch, int node)
s->migrate(s, vector, count, node, private);
}
+#ifdef CONFIG_SMO_NODE
+/*
+ * kmem_cache_move() - Attempt to move all slab objects.
+ * @s: The cache we are working on.
+ * @node: The node to move objects away from.
+ * @target_node: The node to move objects on to.
+ *
+ * Attempts to move all objects (partial slabs and full slabs) to target
+ * node.
+ *
+ * Context: Takes the list_lock.
+ * Return: The number of slabs remaining on node.
+ */
+static unsigned long kmem_cache_move(struct kmem_cache *s,
+ int node, int target_node)
+{
+ struct kmem_cache_node *n = get_node(s, node);
+ LIST_HEAD(move_list);
+ struct page *page, *page2;
+ unsigned long flags;
+ void **scratch;
+
+ if (!s->migrate) {
+ pr_warn("%s SMO not enabled, cannot move objects\n", s->name);
+ goto out;
+ }
+
+ scratch = alloc_scratch(s);
+ if (!scratch)
+ goto out;
+
+ spin_lock_irqsave(&n->list_lock, flags);
+
+ list_for_each_entry_safe(page, page2, &n->partial, lru) {
+ if (!slab_trylock(page))
+ /* Busy slab. Get out of the way */
+ continue;
+
+ if (page->inuse) {
+ list_move(&page->lru, &move_list);
+ /* Stop page being considered for allocations */
+ n->nr_partial--;
+ page->frozen = 1;
+
+ slab_unlock(page);
+ } else { /* Empty slab page */
+ list_del(&page->lru);
+ n->nr_partial--;
+ slab_unlock(page);
+ discard_slab(s, page);
+ }
+ }
+ list_for_each_entry_safe(page, page2, &n->full, lru) {
+ if (!slab_trylock(page))
+ continue;
+
+ list_move(&page->lru, &move_list);
+ page->frozen = 1;
+ slab_unlock(page);
+ }
+
+ spin_unlock_irqrestore(&n->list_lock, flags);
+
+ list_for_each_entry(page, &move_list, lru) {
+ if (page->inuse)
+ move_slab_page(page, scratch, target_node);
+ }
+ kfree(scratch);
+
+ /* Bail here to save taking the list_lock */
+ if (list_empty(&move_list))
+ goto out;
+
+ /* Inspect results and dispose of pages */
+ spin_lock_irqsave(&n->list_lock, flags);
+ list_for_each_entry_safe(page, page2, &move_list, lru) {
+ list_del(&page->lru);
+ slab_lock(page);
+ page->frozen = 0;
+
+ if (page->inuse) {
+ if (page->inuse == page->objects) {
+ list_add(&page->lru, &n->full);
+ slab_unlock(page);
+ } else {
+ n->nr_partial++;
+ list_add_tail(&page->lru, &n->partial);
+ slab_unlock(page);
+ }
+ } else {
+ slab_unlock(page);
+ discard_slab(s, page);
+ }
+ }
+ spin_unlock_irqrestore(&n->list_lock, flags);
+out:
+ return atomic_long_read(&n->nr_slabs);
+}
+#endif /* CONFIG_SMO_NODE */
+
/*
* kmem_cache_defrag() - Defragment node.
* @s: cache we are working on.
@@ -4459,6 +4559,32 @@ static unsigned long kmem_cache_defrag(struct kmem_cache *s,
return n->nr_partial;
}
+#ifdef CONFIG_SMO_NODE
+/*
+ * kmem_cache_move_to_node() - Move all slab objects to node.
+ * @s: The cache we are working on.
+ * @node: The target node to move objects to.
+ *
+ * Attempt to move all slab objects from all nodes to @node.
+ *
+ * Return: The total number of slabs left on emptied nodes.
+ */
+static unsigned long kmem_cache_move_to_node(struct kmem_cache *s, int node)
+{
+ unsigned long left = 0;
+ int nid;
+
+ for_each_node_state(nid, N_NORMAL_MEMORY) {
+ if (nid == node)
+ continue;
+
+ left += kmem_cache_move(s, nid, node);
+ }
+
+ return left;
+}
+#endif
+
/**
* kmem_defrag_slabs() - Defrag slab caches.
* @node: The node to defrag or -1 for all nodes.
@@ -5603,6 +5729,126 @@ static ssize_t shrink_store(struct kmem_cache *s,
}
SLAB_ATTR(shrink);
+#ifdef CONFIG_SMO_NODE
+static ssize_t move_show(struct kmem_cache *s, char *buf)
+{
+ return 0;
+}
+
+/*
+ * parse_move_store_input() - Parse buf getting integer arguments.
+ * @buf: Buffer to parse.
+ * @length: Length of @buf.
+ * @arg0: Return parameter, first argument.
+ * @arg1: Return parameter, second argument.
+ *
+ * Parses the input from user write to sysfs file 'move'. Input string
+ * should contain either one or two node specifiers of form Nx where x
+ * is an integer specifying the NUMA node ID. 'N' or 'n' may be used.
+ * n/N may be omitted.
+ *
+ * e.g.
+ * echo 'N1' > /sysfs/kernel/slab/cache/move
+ * or
+ * echo 'N0 N2' > /sysfs/kernel/slab/cache/move
+ *
+ * Regex matching accepted forms: '[nN]?[0-9]( [nN]?[0-9])?'
+ *
+ * FIXME: This is really fragile. Input must be exactly correct,
+ * spurious whitespace causes parse errors.
+ *
+ * Return: 0 if an argument was successfully converted, or an error code.
+ */
+static ssize_t parse_move_store_input(const char *buf, size_t length,
+ long *arg0, long *arg1)
+{
+ char *s, *save, *ptr;
+ int ret = 0;
+
+ if (!buf)
+ return -EINVAL;
+
+ s = kstrdup(buf, GFP_KERNEL);
+ if (!s)
+ return -ENOMEM;
+ save = s;
+
+ if (s[length - 1] == '\n') {
+ s[length - 1] = '\0';
+ length--;
+ }
+
+ ptr = strsep(&s, " ");
+ if (!ptr || strcmp(ptr, "") == 0) {
+ ret = 0;
+ goto out;
+ }
+
+ if (*ptr == 'N' || *ptr == 'n')
+ ptr++;
+ ret = kstrtol(ptr, 10, arg0);
+ if (ret < 0)
+ goto out;
+
+ if (s) {
+ if (*s == 'N' || *s == 'n')
+ s++;
+ ret = kstrtol(s, 10, arg1);
+ if (ret < 0)
+ goto out;
+ }
+
+ ret = 0;
+out:
+ kfree(save);
+ return ret;
+}
+
+static bool is_valid_node(int node)
+{
+ int nid;
+
+ for_each_node_state(nid, N_NORMAL_MEMORY) {
+ if (nid == node)
+ return true;
+ }
+ return false;
+}
+
+/*
+ * move_store() - Move objects between nodes.
+ * @s: The cache we are working on.
+ * @buf: String received.
+ * @length: Length of @buf.
+ *
+ * Writes to /sys/kernel/slab/<cache>/move are interpreted as follows:
+ *
+ * echo "N1" > move : Move all objects (from all nodes) to node 1.
+ * echo "N0 N1" > move : Move all objects from node 0 to node 1.
+ *
+ * 'N' may be omitted:
+ */
+static ssize_t move_store(struct kmem_cache *s, const char *buf, size_t length)
+{
+ long arg0 = -1;
+ long arg1 = -1;
+ int ret;
+
+ ret = parse_move_store_input(buf, length, &arg0, &arg1);
+ if (ret < 0)
+ return -EINVAL;
+
+ if (is_valid_node(arg0) && is_valid_node(arg1))
+ (void)kmem_cache_move(s, arg0, arg1);
+ else if (is_valid_node(arg0))
+ (void)kmem_cache_move_to_node(s, arg0);
+
+ /* FIXME: What should we be returning here? */
+ return length;
+}
+SLAB_ATTR(move);
+#endif /* CONFIG_SMO_NODE */
+
#ifdef CONFIG_NUMA
static ssize_t remote_node_defrag_ratio_show(struct kmem_cache *s, char *buf)
{
@@ -5727,6 +5973,9 @@ static struct attribute *slab_attrs[] = {
&reclaim_account_attr.attr,
&destroy_by_rcu_attr.attr,
&shrink_attr.attr,
+#ifdef CONFIG_SMO_NODE
+ &move_attr.attr,
+#endif
&slabs_cpu_partial_attr.attr,
#ifdef CONFIG_SLUB_DEBUG
&total_objects_attr.attr,
--
2.21.0
^ permalink raw reply related [flat|nested] 28+ messages in thread* [RFC PATCH v2 12/14] slub: Enable balancing slabs across nodes
2019-04-03 4:21 [RFC PATCH v2 00/14] Slab Movable Objects (SMO) Tobin C. Harding
` (10 preceding siblings ...)
2019-04-03 4:21 ` [RFC PATCH v2 11/14] slub: Enable moving objects to/from specific nodes Tobin C. Harding
@ 2019-04-03 4:21 ` Tobin C. Harding
2019-04-03 4:21 ` [RFC PATCH v2 13/14] dcache: Provide a dentry constructor Tobin C. Harding
2019-04-03 4:21 ` [RFC PATCH v2 14/14] dcache: Implement object migration Tobin C. Harding
13 siblings, 0 replies; 28+ messages in thread
From: Tobin C. Harding @ 2019-04-03 4:21 UTC (permalink / raw)
To: Andrew Morton
Cc: Tobin C. Harding, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel
We have just implemented Slab Movable Objects (SMO). On NUMA systems
slabs can become unbalanced i.e. many slabs on one node while other
nodes have few slabs. Using SMO we can balance the slabs across all
the nodes.
The algorithm used is as follows:
1. Move all objects to node 0 (this has the effect of defragmenting the
cache).
2. Calculate the desired number of slabs for each node (this is done
using the approximation nr_slabs / nr_nodes).
3. Loop over the nodes moving the desired number of slabs from node 0
to the node.
Feature is conditionally built in with CONFIG_SMO_NODE, this is because
we need the full list (we enable SLUB_DEBUG to get this). Future
version may separate final list out of SLUB_DEBUG.
Expose this functionality to userspace via a sysfs entry. Add sysfs
entry:
/sysfs/kernel/slab/<cache>/balance
Write of '1' to this file triggers balance, no other value accepted.
This feature relies on SMO being enable for the cache, this is done with
a call to, after the isolate/migrate functions have been defined.
kmem_cache_setup_mobility(s, isolate, migrate)
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
---
mm/slub.c | 120 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 120 insertions(+)
diff --git a/mm/slub.c b/mm/slub.c
index e4f3dde443f5..a5c48c41d72b 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4583,6 +4583,109 @@ static unsigned long kmem_cache_move_to_node(struct kmem_cache *s, int node)
return left;
}
+
+/*
+ * kmem_cache_move_slabs() - Attempt to move @num slabs to target_node,
+ * @s: The cache we are working on.
+ * @node: The node to move objects from.
+ * @target_node: The node to move objects to.
+ * @num: The number of slabs to move.
+ *
+ * Attempts to move @num slabs from @node to @target_node. This is done
+ * by migrating objects from slabs on the full_list.
+ *
+ * Return: The number of slabs moved or error code.
+ */
+static long kmem_cache_move_slabs(struct kmem_cache *s,
+ int node, int target_node, long num)
+{
+ struct kmem_cache_node *n = get_node(s, node);
+ LIST_HEAD(move_list);
+ struct page *page, *page2;
+ unsigned long flags;
+ void **scratch;
+ long done = 0;
+
+ if (node == target_node)
+ return -EINVAL;
+
+ scratch = alloc_scratch(s);
+ if (!scratch)
+ return -ENOMEM;
+
+ spin_lock_irqsave(&n->list_lock, flags);
+ list_for_each_entry_safe(page, page2, &n->full, lru) {
+ if (!slab_trylock(page))
+ /* Busy slab. Get out of the way */
+ continue;
+
+ list_move(&page->lru, &move_list);
+ page->frozen = 1;
+ slab_unlock(page);
+
+ if (++done >= num)
+ break;
+ }
+ spin_unlock_irqrestore(&n->list_lock, flags);
+
+ list_for_each_entry(page, &move_list, lru) {
+ if (page->inuse)
+ move_slab_page(page, scratch, target_node);
+ }
+ kfree(scratch);
+
+ /* Inspect results and dispose of pages */
+ spin_lock_irqsave(&n->list_lock, flags);
+ list_for_each_entry_safe(page, page2, &move_list, lru) {
+ list_del(&page->lru);
+ slab_lock(page);
+ page->frozen = 0;
+
+ if (page->inuse) {
+ /*
+ * This is best effort only, if slab still has
+ * objects just put it back on the partial list.
+ */
+ n->nr_partial++;
+ list_add_tail(&page->lru, &n->partial);
+ slab_unlock(page);
+ } else {
+ slab_unlock(page);
+ discard_slab(s, page);
+ }
+ }
+ spin_unlock_irqrestore(&n->list_lock, flags);
+
+ return done;
+}
+
+/*
+ * kmem_cache_balance_nodes() - Balance slabs across nodes.
+ * @s: The cache we are working on.
+ */
+static void kmem_cache_balance_nodes(struct kmem_cache *s)
+{
+ struct kmem_cache_node *n = get_node(s, 0);
+ unsigned long desired_nr_slabs_per_node;
+ unsigned long nr_slabs;
+ int nr_nodes = 0;
+ int nid;
+
+ (void)kmem_cache_move_to_node(s, 0);
+
+ for_each_node_state(nid, N_NORMAL_MEMORY)
+ nr_nodes++;
+
+ nr_slabs = atomic_long_read(&n->nr_slabs);
+ desired_nr_slabs_per_node = nr_slabs / nr_nodes;
+
+ for_each_node_state(nid, N_NORMAL_MEMORY) {
+ if (nid == 0)
+ continue;
+
+ kmem_cache_move_slabs(s, 0, nid, desired_nr_slabs_per_node);
+ }
+}
#endif
/**
@@ -5847,6 +5950,22 @@ static ssize_t move_store(struct kmem_cache *s, const char *buf, size_t length)
return length;
}
SLAB_ATTR(move);
+
+static ssize_t balance_show(struct kmem_cache *s, char *buf)
+{
+ return 0;
+}
+
+static ssize_t balance_store(struct kmem_cache *s,
+ const char *buf, size_t length)
+{
+ if (buf[0] == '1')
+ kmem_cache_balance_nodes(s);
+ else
+ return -EINVAL;
+ return length;
+}
+SLAB_ATTR(balance);
#endif /* CONFIG_SMO_NODE */
#ifdef CONFIG_NUMA
@@ -5975,6 +6094,7 @@ static struct attribute *slab_attrs[] = {
&shrink_attr.attr,
#ifdef CONFIG_SMO_NODE
&move_attr.attr,
+ &balance_attr.attr,
#endif
&slabs_cpu_partial_attr.attr,
#ifdef CONFIG_SLUB_DEBUG
--
2.21.0
^ permalink raw reply related [flat|nested] 28+ messages in thread* [RFC PATCH v2 13/14] dcache: Provide a dentry constructor
2019-04-03 4:21 [RFC PATCH v2 00/14] Slab Movable Objects (SMO) Tobin C. Harding
` (11 preceding siblings ...)
2019-04-03 4:21 ` [RFC PATCH v2 12/14] slub: Enable balancing slabs across nodes Tobin C. Harding
@ 2019-04-03 4:21 ` Tobin C. Harding
2019-04-03 4:21 ` [RFC PATCH v2 14/14] dcache: Implement object migration Tobin C. Harding
13 siblings, 0 replies; 28+ messages in thread
From: Tobin C. Harding @ 2019-04-03 4:21 UTC (permalink / raw)
To: Andrew Morton
Cc: Tobin C. Harding, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel
In order to support object migration on the dentry cache we need to have
a determined object state at all times. Without a constructor the object
would have a random state after allocation.
Provide a dentry constructor.
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
---
fs/dcache.c | 37 ++++++++++++++++++++++++++++---------
1 file changed, 28 insertions(+), 9 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index aac41adf4743..606844ad5171 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1603,6 +1603,22 @@ void d_invalidate(struct dentry *dentry)
}
EXPORT_SYMBOL(d_invalidate);
+static void dcache_ctor(void *p)
+{
+ struct dentry *dentry = p;
+
+ dentry->d_lockref.count = 0;
+ dentry->d_inode = NULL;
+
+ spin_lock_init(&dentry->d_lock);
+
+ INIT_HLIST_BL_NODE(&dentry->d_hash);
+ INIT_LIST_HEAD(&dentry->d_lru);
+ INIT_LIST_HEAD(&dentry->d_subdirs);
+ INIT_HLIST_NODE(&dentry->d_u.d_alias);
+ INIT_LIST_HEAD(&dentry->d_child);
+}
+
/**
* __d_alloc - allocate a dcache entry
* @sb: filesystem it will belong to
@@ -1658,7 +1674,7 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
dentry->d_lockref.count = 1;
dentry->d_flags = 0;
- spin_lock_init(&dentry->d_lock);
+
seqcount_init(&dentry->d_seq);
dentry->d_inode = NULL;
dentry->d_parent = dentry;
@@ -3091,14 +3107,17 @@ static void __init dcache_init_early(void)
static void __init dcache_init(void)
{
- /*
- * A constructor could be added for stable state like the lists,
- * but it is probably not worth it because of the cache nature
- * of the dcache.
- */
- dentry_cache = KMEM_CACHE_USERCOPY(dentry,
- SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD|SLAB_ACCOUNT,
- d_iname);
+ slab_flags_t flags =
+ SLAB_RECLAIM_ACCOUNT | SLAB_PANIC | SLAB_MEM_SPREAD | SLAB_ACCOUNT;
+
+ dentry_cache =
+ kmem_cache_create_usercopy("dentry",
+ sizeof(struct dentry),
+ __alignof__(struct dentry),
+ flags,
+ offsetof(struct dentry, d_iname),
+ sizeof_field(struct dentry, d_iname),
+ dcache_ctor);
/* Hash may have been set up in dcache_init_early */
if (!hashdist)
--
2.21.0
^ permalink raw reply related [flat|nested] 28+ messages in thread* [RFC PATCH v2 14/14] dcache: Implement object migration
2019-04-03 4:21 [RFC PATCH v2 00/14] Slab Movable Objects (SMO) Tobin C. Harding
` (12 preceding siblings ...)
2019-04-03 4:21 ` [RFC PATCH v2 13/14] dcache: Provide a dentry constructor Tobin C. Harding
@ 2019-04-03 4:21 ` Tobin C. Harding
2019-04-03 17:08 ` Al Viro
13 siblings, 1 reply; 28+ messages in thread
From: Tobin C. Harding @ 2019-04-03 4:21 UTC (permalink / raw)
To: Andrew Morton
Cc: Tobin C. Harding, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel
The dentry slab cache is susceptible to internal fragmentation. Now
that we have Slab Movable Objects we can defragment the dcache. Object
migration is only possible for dentry objects that are not currently
referenced by anyone, i.e. we are using the object migration
infrastructure to free unused dentries.
Implement isolate and migrate functions for the dentry slab cache.
Signed-off-by: Tobin C. Harding <tobin@kernel.org>
---
fs/dcache.c | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 87 insertions(+)
diff --git a/fs/dcache.c b/fs/dcache.c
index 606844ad5171..4387715b7ebb 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -30,6 +30,7 @@
#include <linux/bit_spinlock.h>
#include <linux/rculist_bl.h>
#include <linux/list_lru.h>
+#include <linux/backing-dev.h>
#include "internal.h"
#include "mount.h"
@@ -3074,6 +3075,90 @@ void d_tmpfile(struct dentry *dentry, struct inode *inode)
}
EXPORT_SYMBOL(d_tmpfile);
+/*
+ * d_isolate() - Dentry isolation callback function.
+ * @s: The dentry cache.
+ * @v: Vector of pointers to the objects to migrate.
+ * @nr: Number of objects in @v.
+ *
+ * The slab allocator is holding off frees. We can safely examine
+ * the object without the danger of it vanishing from under us.
+ */
+static void *d_isolate(struct kmem_cache *s, void **v, int nr)
+{
+ struct dentry *dentry;
+ int i;
+
+ for (i = 0; i < nr; i++) {
+ dentry = v[i];
+ spin_lock(&dentry->d_lock);
+ /*
+ * Three sorts of dentries cannot be reclaimed:
+ *
+ * 1. dentries that are in the process of being allocated
+ * or being freed. In that case the dentry is neither
+ * on the LRU nor hashed.
+ *
+ * 2. Fake hashed entries as used for anonymous dentries
+ * and pipe I/O. The fake hashed entries have d_flags
+ * set to indicate a hashed entry. However, the
+ * d_hash field indicates that the entry is not hashed.
+ *
+ * 3. dentries that have a backing store that is not
+ * writable. This is true for tmpsfs and other in
+ * memory filesystems. Removing dentries from them
+ * would loose dentries for good.
+ */
+ if ((d_unhashed(dentry) && list_empty(&dentry->d_lru)) ||
+ (!d_unhashed(dentry) && hlist_bl_unhashed(&dentry->d_hash)) ||
+ (dentry->d_inode &&
+ !mapping_cap_writeback_dirty(dentry->d_inode->i_mapping))) {
+ /* Ignore this dentry */
+ v[i] = NULL;
+ } else {
+ __dget_dlock(dentry);
+ }
+ spin_unlock(&dentry->d_lock);
+ }
+ return NULL; /* No need for private data */
+}
+
+/*
+ * d_migrate() - Dentry migration callback function.
+ * @s: The dentry cache.
+ * @v: Vector of pointers to the objects to migrate.
+ * @nr: Number of objects in @v.
+ * @node: The NUMA node where new object should be allocated.
+ * @private: Returned by d_isolate() (currently %NULL).
+ *
+ * Slab has dropped all the locks. Get rid of the refcount obtained
+ * earlier and also free the object.
+ */
+static void d_migrate(struct kmem_cache *s, void **v, int nr,
+ int node, void *_unused)
+{
+ struct dentry *dentry;
+ int i;
+
+ for (i = 0; i < nr; i++) {
+ dentry = v[i];
+ if (dentry)
+ d_invalidate(dentry);
+ }
+
+ for (i = 0; i < nr; i++) {
+ dentry = v[i];
+ if (dentry)
+ dput(dentry);
+ }
+
+ /*
+ * dentries are freed using RCU so we need to wait until RCU
+ * operations are complete.
+ */
+ synchronize_rcu();
+}
+
static __initdata unsigned long dhash_entries;
static int __init set_dhash_entries(char *str)
{
@@ -3119,6 +3204,8 @@ static void __init dcache_init(void)
sizeof_field(struct dentry, d_iname),
dcache_ctor);
+ kmem_cache_setup_mobility(dentry_cache, d_isolate, d_migrate);
+
/* Hash may have been set up in dcache_init_early */
if (!hashdist)
return;
--
2.21.0
^ permalink raw reply related [flat|nested] 28+ messages in thread* Re: [RFC PATCH v2 14/14] dcache: Implement object migration
2019-04-03 4:21 ` [RFC PATCH v2 14/14] dcache: Implement object migration Tobin C. Harding
@ 2019-04-03 17:08 ` Al Viro
2019-04-03 17:19 ` Al Viro
2019-04-03 17:56 ` Christopher Lameter
0 siblings, 2 replies; 28+ messages in thread
From: Al Viro @ 2019-04-03 17:08 UTC (permalink / raw)
To: Tobin C. Harding
Cc: Andrew Morton, Roman Gushchin, Alexander Viro, Christoph Hellwig,
Pekka Enberg, David Rientjes, Joonsoo Kim, Christopher Lameter,
Matthew Wilcox, Miklos Szeredi, Andreas Dilger, Waiman Long,
Tycho Andersen, Theodore Ts'o, Andi Kleen, David Chinner,
Nick Piggin, Rik van Riel, Hugh Dickins, linux-mm, linux-fsdevel,
linux-kernel, Linus Torvalds
On Wed, Apr 03, 2019 at 03:21:27PM +1100, Tobin C. Harding wrote:
> The dentry slab cache is susceptible to internal fragmentation. Now
> that we have Slab Movable Objects we can defragment the dcache. Object
> migration is only possible for dentry objects that are not currently
> referenced by anyone, i.e. we are using the object migration
> infrastructure to free unused dentries.
>
> Implement isolate and migrate functions for the dentry slab cache.
> + /*
> + * Three sorts of dentries cannot be reclaimed:
> + *
> + * 1. dentries that are in the process of being allocated
> + * or being freed. In that case the dentry is neither
> + * on the LRU nor hashed.
> + *
> + * 2. Fake hashed entries as used for anonymous dentries
> + * and pipe I/O. The fake hashed entries have d_flags
> + * set to indicate a hashed entry. However, the
> + * d_hash field indicates that the entry is not hashed.
> + *
> + * 3. dentries that have a backing store that is not
> + * writable. This is true for tmpsfs and other in
> + * memory filesystems. Removing dentries from them
> + * would loose dentries for good.
> + */
> + if ((d_unhashed(dentry) && list_empty(&dentry->d_lru)) ||
> + (!d_unhashed(dentry) && hlist_bl_unhashed(&dentry->d_hash)) ||
> + (dentry->d_inode &&
> + !mapping_cap_writeback_dirty(dentry->d_inode->i_mapping))) {
> + /* Ignore this dentry */
> + v[i] = NULL;
> + } else {
> + __dget_dlock(dentry);
> + }
> + spin_unlock(&dentry->d_lock);
> + }
> + return NULL; /* No need for private data */
> +}
> +
> +/*
> + * d_migrate() - Dentry migration callback function.
> + * @s: The dentry cache.
> + * @v: Vector of pointers to the objects to migrate.
> + * @nr: Number of objects in @v.
> + * @node: The NUMA node where new object should be allocated.
> + * @private: Returned by d_isolate() (currently %NULL).
> + *
> + * Slab has dropped all the locks. Get rid of the refcount obtained
> + * earlier and also free the object.
> + */
> +static void d_migrate(struct kmem_cache *s, void **v, int nr,
> + int node, void *_unused)
> +{
> + struct dentry *dentry;
> + int i;
> +
> + for (i = 0; i < nr; i++) {
> + dentry = v[i];
> + if (dentry)
> + d_invalidate(dentry);
Oh, *brilliant*
Let's do d_invalidate() on random dentries and hope they go away.
With convoluted and brittle logics for deciding which ones to
spare, which is actually wrong. This will pick mountpoints
and tear them out, to start with.
NAKed-by: Al Viro <viro@zeniv.linux.org.uk>
And this is a NAK for the entire approach; if it has a positive refcount,
LEAVE IT ALONE. Period. Don't play this kind of games, they are wrong.
d_invalidate() is not something that can be done to an arbitrary dentry.
^ permalink raw reply [flat|nested] 28+ messages in thread* Re: [RFC PATCH v2 14/14] dcache: Implement object migration
2019-04-03 17:08 ` Al Viro
@ 2019-04-03 17:19 ` Al Viro
2019-04-03 17:48 ` Al Viro
2019-04-04 21:18 ` Tobin C. Harding
2019-04-03 17:56 ` Christopher Lameter
1 sibling, 2 replies; 28+ messages in thread
From: Al Viro @ 2019-04-03 17:19 UTC (permalink / raw)
To: Tobin C. Harding
Cc: Andrew Morton, Roman Gushchin, Alexander Viro, Christoph Hellwig,
Pekka Enberg, David Rientjes, Joonsoo Kim, Christopher Lameter,
Matthew Wilcox, Miklos Szeredi, Andreas Dilger, Waiman Long,
Tycho Andersen, Theodore Ts'o, Andi Kleen, David Chinner,
Nick Piggin, Rik van Riel, Hugh Dickins, linux-mm, linux-fsdevel,
linux-kernel, Linus Torvalds
On Wed, Apr 03, 2019 at 06:08:11PM +0100, Al Viro wrote:
> Oh, *brilliant*
>
> Let's do d_invalidate() on random dentries and hope they go away.
> With convoluted and brittle logics for deciding which ones to
> spare, which is actually wrong. This will pick mountpoints
> and tear them out, to start with.
>
> NAKed-by: Al Viro <viro@zeniv.linux.org.uk>
>
> And this is a NAK for the entire approach; if it has a positive refcount,
> LEAVE IT ALONE. Period. Don't play this kind of games, they are wrong.
> d_invalidate() is not something that can be done to an arbitrary dentry.
PS: "try to evict what can be evicted out of this set" can be done, but
you want something like
start with empty list
go through your array of references
grab dentry->d_lock
if dentry->d_lockref.count is not zero
unlock and continue
if dentry->d_flags & DCACHE_SHRINK_LIST
ditto, it's not for us to play with
if (dentry->d_flags & DCACHE_LRU_LIST)
d_lru_del(dentry);
d_shrink_add(dentry, &list);
unlock
on the collection phase and
if the list is not empty by the end of that loop
shrink_dentry_list(&list);
on the disposal.
^ permalink raw reply [flat|nested] 28+ messages in thread* Re: [RFC PATCH v2 14/14] dcache: Implement object migration
2019-04-03 17:19 ` Al Viro
@ 2019-04-03 17:48 ` Al Viro
2019-04-04 20:29 ` Tobin C. Harding
2019-04-04 21:18 ` Tobin C. Harding
1 sibling, 1 reply; 28+ messages in thread
From: Al Viro @ 2019-04-03 17:48 UTC (permalink / raw)
To: Tobin C. Harding
Cc: Andrew Morton, Roman Gushchin, Alexander Viro, Christoph Hellwig,
Pekka Enberg, David Rientjes, Joonsoo Kim, Christopher Lameter,
Matthew Wilcox, Miklos Szeredi, Andreas Dilger, Waiman Long,
Tycho Andersen, Theodore Ts'o, Andi Kleen, David Chinner,
Nick Piggin, Rik van Riel, Hugh Dickins, linux-mm, linux-fsdevel,
linux-kernel, Linus Torvalds
On Wed, Apr 03, 2019 at 06:19:21PM +0100, Al Viro wrote:
> On Wed, Apr 03, 2019 at 06:08:11PM +0100, Al Viro wrote:
>
> > Oh, *brilliant*
> >
> > Let's do d_invalidate() on random dentries and hope they go away.
> > With convoluted and brittle logics for deciding which ones to
> > spare, which is actually wrong. This will pick mountpoints
> > and tear them out, to start with.
> >
> > NAKed-by: Al Viro <viro@zeniv.linux.org.uk>
> >
> > And this is a NAK for the entire approach; if it has a positive refcount,
> > LEAVE IT ALONE. Period. Don't play this kind of games, they are wrong.
> > d_invalidate() is not something that can be done to an arbitrary dentry.
>
> PS: "try to evict what can be evicted out of this set" can be done, but
> you want something like
> start with empty list
> go through your array of references
> grab dentry->d_lock
> if dentry->d_lockref.count is not zero
> unlock and continue
> if dentry->d_flags & DCACHE_SHRINK_LIST
> ditto, it's not for us to play with
> if (dentry->d_flags & DCACHE_LRU_LIST)
> d_lru_del(dentry);
> d_shrink_add(dentry, &list);
> unlock
>
> on the collection phase and
> if the list is not empty by the end of that loop
> shrink_dentry_list(&list);
> on the disposal.
Note, BTW, that your constructor is wrong - all it really needs to do
is spin_lock_init() and setting ->d_lockref.count same as lockref_mark_dead()
does, to match the state of dentries being torn down.
__d_alloc() is not holding ->d_lock, since the object is not visible to
anybody else yet; with your changes it *is* visible. However, if the
assignment to ->d_lockref.count in __d_alloc() is guaranteed to be
non-zero to non-zero, the above should be safe.
^ permalink raw reply [flat|nested] 28+ messages in thread
* Re: [RFC PATCH v2 14/14] dcache: Implement object migration
2019-04-03 17:48 ` Al Viro
@ 2019-04-04 20:29 ` Tobin C. Harding
2019-04-04 21:58 ` Al Viro
0 siblings, 1 reply; 28+ messages in thread
From: Tobin C. Harding @ 2019-04-04 20:29 UTC (permalink / raw)
To: Al Viro
Cc: Tobin C. Harding, Andrew Morton, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel,
Linus Torvalds
On Wed, Apr 03, 2019 at 06:48:55PM +0100, Al Viro wrote:
> On Wed, Apr 03, 2019 at 06:19:21PM +0100, Al Viro wrote:
> > On Wed, Apr 03, 2019 at 06:08:11PM +0100, Al Viro wrote:
> >
> > > Oh, *brilliant*
> > >
> > > Let's do d_invalidate() on random dentries and hope they go away.
> > > With convoluted and brittle logics for deciding which ones to
> > > spare, which is actually wrong. This will pick mountpoints
> > > and tear them out, to start with.
> > >
> > > NAKed-by: Al Viro <viro@zeniv.linux.org.uk>
> > >
> > > And this is a NAK for the entire approach; if it has a positive refcount,
> > > LEAVE IT ALONE. Period. Don't play this kind of games, they are wrong.
> > > d_invalidate() is not something that can be done to an arbitrary dentry.
> >
> > PS: "try to evict what can be evicted out of this set" can be done, but
> > you want something like
> > start with empty list
> > go through your array of references
> > grab dentry->d_lock
> > if dentry->d_lockref.count is not zero
> > unlock and continue
> > if dentry->d_flags & DCACHE_SHRINK_LIST
> > ditto, it's not for us to play with
> > if (dentry->d_flags & DCACHE_LRU_LIST)
> > d_lru_del(dentry);
> > d_shrink_add(dentry, &list);
> > unlock
> >
> > on the collection phase and
> > if the list is not empty by the end of that loop
> > shrink_dentry_list(&list);
> > on the disposal.
>
> Note, BTW, that your constructor is wrong - all it really needs to do
> is spin_lock_init() and setting ->d_lockref.count same as lockref_mark_dead()
> does, to match the state of dentries being torn down.
Thanks for looking at this Al.
> __d_alloc() is not holding ->d_lock, since the object is not visible to
> anybody else yet; with your changes it *is* visible.
I don't quite understand this comment. How is the object visible? The
constructor is only called when allocating a new page to the slab and
this is done with interrupts disabled.
> However, if the
> assignment to ->d_lockref.count in __d_alloc() is guaranteed to be
> non-zero to non-zero, the above should be safe.
I've done as you suggest and set it to -128
Thanks for schooling me on the VFS stuff.
Tobin
^ permalink raw reply [flat|nested] 28+ messages in thread
* Re: [RFC PATCH v2 14/14] dcache: Implement object migration
2019-04-04 20:29 ` Tobin C. Harding
@ 2019-04-04 21:58 ` Al Viro
0 siblings, 0 replies; 28+ messages in thread
From: Al Viro @ 2019-04-04 21:58 UTC (permalink / raw)
To: Tobin C. Harding
Cc: Tobin C. Harding, Andrew Morton, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel,
Linus Torvalds
On Fri, Apr 05, 2019 at 07:29:14AM +1100, Tobin C. Harding wrote:
> > __d_alloc() is not holding ->d_lock, since the object is not visible to
> > anybody else yet; with your changes it *is* visible.
>
> I don't quite understand this comment. How is the object visible? The
> constructor is only called when allocating a new page to the slab and
> this is done with interrupts disabled.
Not to constructor, to your try-to-evict code...
^ permalink raw reply [flat|nested] 28+ messages in thread
* Re: [RFC PATCH v2 14/14] dcache: Implement object migration
2019-04-03 17:19 ` Al Viro
2019-04-03 17:48 ` Al Viro
@ 2019-04-04 21:18 ` Tobin C. Harding
1 sibling, 0 replies; 28+ messages in thread
From: Tobin C. Harding @ 2019-04-04 21:18 UTC (permalink / raw)
To: Al Viro
Cc: Tobin C. Harding, Andrew Morton, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Christopher Lameter, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel,
Linus Torvalds
On Wed, Apr 03, 2019 at 06:19:21PM +0100, Al Viro wrote:
> On Wed, Apr 03, 2019 at 06:08:11PM +0100, Al Viro wrote:
>
> > Oh, *brilliant*
> >
> > Let's do d_invalidate() on random dentries and hope they go away.
> > With convoluted and brittle logics for deciding which ones to
> > spare, which is actually wrong. This will pick mountpoints
> > and tear them out, to start with.
> >
> > NAKed-by: Al Viro <viro@zeniv.linux.org.uk>
> >
> > And this is a NAK for the entire approach; if it has a positive refcount,
> > LEAVE IT ALONE. Period. Don't play this kind of games, they are wrong.
> > d_invalidate() is not something that can be done to an arbitrary dentry.
>
> PS: "try to evict what can be evicted out of this set" can be done, but
> you want something like
> start with empty list
> go through your array of references
> grab dentry->d_lock
> if dentry->d_lockref.count is not zero
> unlock and continue
> if dentry->d_flags & DCACHE_SHRINK_LIST
> ditto, it's not for us to play with
> if (dentry->d_flags & DCACHE_LRU_LIST)
> d_lru_del(dentry);
> d_shrink_add(dentry, &list);
> unlock
>
> on the collection phase and
> if the list is not empty by the end of that loop
> shrink_dentry_list(&list);
> on the disposal.
Implemented as suggested, thanks. RFCv3 to come when we have some stats
for you :)
thanks,
Tobin.
^ permalink raw reply [flat|nested] 28+ messages in thread
* Re: [RFC PATCH v2 14/14] dcache: Implement object migration
2019-04-03 17:08 ` Al Viro
2019-04-03 17:19 ` Al Viro
@ 2019-04-03 17:56 ` Christopher Lameter
2019-04-03 18:24 ` Al Viro
1 sibling, 1 reply; 28+ messages in thread
From: Christopher Lameter @ 2019-04-03 17:56 UTC (permalink / raw)
To: Al Viro
Cc: Tobin C. Harding, Andrew Morton, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Matthew Wilcox, Miklos Szeredi, Andreas Dilger, Waiman Long,
Tycho Andersen, Theodore Ts'o, Andi Kleen, David Chinner,
Nick Piggin, Rik van Riel, Hugh Dickins, linux-mm, linux-fsdevel,
linux-kernel, Linus Torvalds
On Wed, 3 Apr 2019, Al Viro wrote:
> Let's do d_invalidate() on random dentries and hope they go away.
> With convoluted and brittle logics for deciding which ones to
> spare, which is actually wrong. This will pick mountpoints
> and tear them out, to start with.
>
> NAKed-by: Al Viro <viro@zeniv.linux.org.uk>
>
> And this is a NAK for the entire approach; if it has a positive refcount,
> LEAVE IT ALONE. Period. Don't play this kind of games, they are wrong.
> d_invalidate() is not something that can be done to an arbitrary dentry.
Well could you help us figure out how to do it the right way? We (the MM
guys) are having a hard time not being familiar with the filesystem stuff.
This is an RFC and we want to know how to do this right.
^ permalink raw reply [flat|nested] 28+ messages in thread
* Re: [RFC PATCH v2 14/14] dcache: Implement object migration
2019-04-03 17:56 ` Christopher Lameter
@ 2019-04-03 18:24 ` Al Viro
2019-04-03 19:05 ` Al Viro
2019-04-04 15:46 ` Christopher Lameter
0 siblings, 2 replies; 28+ messages in thread
From: Al Viro @ 2019-04-03 18:24 UTC (permalink / raw)
To: Christopher Lameter
Cc: Tobin C. Harding, Andrew Morton, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Matthew Wilcox, Miklos Szeredi, Andreas Dilger, Waiman Long,
Tycho Andersen, Theodore Ts'o, Andi Kleen, David Chinner,
Nick Piggin, Rik van Riel, Hugh Dickins, linux-mm, linux-fsdevel,
linux-kernel, Linus Torvalds
On Wed, Apr 03, 2019 at 05:56:27PM +0000, Christopher Lameter wrote:
> On Wed, 3 Apr 2019, Al Viro wrote:
>
> > Let's do d_invalidate() on random dentries and hope they go away.
> > With convoluted and brittle logics for deciding which ones to
> > spare, which is actually wrong. This will pick mountpoints
> > and tear them out, to start with.
> >
> > NAKed-by: Al Viro <viro@zeniv.linux.org.uk>
> >
> > And this is a NAK for the entire approach; if it has a positive refcount,
> > LEAVE IT ALONE. Period. Don't play this kind of games, they are wrong.
> > d_invalidate() is not something that can be done to an arbitrary dentry.
>
> Well could you help us figure out how to do it the right way? We (the MM
> guys) are having a hard time not being familiar with the filesystem stuff.
>
> This is an RFC and we want to know how to do this right.
If by "how to do it right" you mean "expedit kicking out something with
non-zero refcount" - there's no way to do that. Nothing even remotely
sane.
If you mean "kick out everything in this page with zero refcount" - that
can be done (see further in the thread).
Look, dentries and inodes are really, really not relocatable. If they
can be evicted by memory pressure - sure, we can do that for a given
set (e.g. "everything in that page"). But that's it - if memory
pressure would _not_ get rid of that one, there's nothing to be done.
Again, all VM can do is to simulate shrinker hitting hard on given
bunch (rather than buggering the entire cache). If filesystem (or
something in VFS) says "it's busy", it bloody well _is_ busy and
won't be going away until it ceases to be such.
^ permalink raw reply [flat|nested] 28+ messages in thread
* Re: [RFC PATCH v2 14/14] dcache: Implement object migration
2019-04-03 18:24 ` Al Viro
@ 2019-04-03 19:05 ` Al Viro
2019-04-04 8:01 ` Miklos Szeredi
2019-04-04 15:46 ` Christopher Lameter
1 sibling, 1 reply; 28+ messages in thread
From: Al Viro @ 2019-04-03 19:05 UTC (permalink / raw)
To: Christopher Lameter
Cc: Tobin C. Harding, Andrew Morton, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Matthew Wilcox, Miklos Szeredi, Andreas Dilger, Waiman Long,
Tycho Andersen, Theodore Ts'o, Andi Kleen, David Chinner,
Nick Piggin, Rik van Riel, Hugh Dickins, linux-mm, linux-fsdevel,
linux-kernel, Linus Torvalds
On Wed, Apr 03, 2019 at 07:24:54PM +0100, Al Viro wrote:
> If by "how to do it right" you mean "expedit kicking out something with
> non-zero refcount" - there's no way to do that. Nothing even remotely
> sane.
>
> If you mean "kick out everything in this page with zero refcount" - that
> can be done (see further in the thread).
>
> Look, dentries and inodes are really, really not relocatable. If they
> can be evicted by memory pressure - sure, we can do that for a given
> set (e.g. "everything in that page"). But that's it - if memory
> pressure would _not_ get rid of that one, there's nothing to be done.
> Again, all VM can do is to simulate shrinker hitting hard on given
> bunch (rather than buggering the entire cache). If filesystem (or
> something in VFS) says "it's busy", it bloody well _is_ busy and
> won't be going away until it ceases to be such.
FWIW, some theory: the only kind of long-term reference that can
be killed off by memory pressure is that from child to parent.
Anything else (e.g. an opened file, current directory, mountpoint,
etc.) is out of limits - it either won't be going away until
the thing is not pinned anymore (close, chdir, etc.) *or*
it really shouldn't be ("VM wants this mountpoint dentry freed,
so just dissolve the mount" is a bloody bad idea for obvious
reasons).
Stuff in somebody's shrink list is none of our business - somebody
else is going to try and evict it anyway; if it can be evicted,
it will be.
Anything with zero refcount that isn't in somebody else's
shrink list is fair game.
Directories with children could, in principle, be helped along -
we could try shrink_dcache_parent() on them, which might end
up leaving them with zero refcount. However, it's not cheap
and if you pick the root dentry of a filesystem, it'll try to
evict everything on it that can be evicted, be it in this page
or not. And there's no promise that it will end up evictable
after that.
So from the correctness POV
* you can kick out everything with zero refcount not
on shrink lists.
* you _might_ try shrink_dcache_parent() on directory
dentries, in hope to drive their refcount to zero. However,
that's almost certainly going to hit too hard and be too costly.
* d_invalidate() is no-go; if anything, you want something
weaker than shrink_dcache_parent(), not stronger.
For anything beyond "just kick out everything in that page that
happens to have zero refcount" I would really like to see the
stats - how much does it help, how costly it is _and_ how much
of the cache does it throw away (see above re running into a root
dentry of some filesystem and essentially trimming dcache for
that fs down to the unevictable stuff).
^ permalink raw reply [flat|nested] 28+ messages in thread* Re: [RFC PATCH v2 14/14] dcache: Implement object migration
2019-04-03 19:05 ` Al Viro
@ 2019-04-04 8:01 ` Miklos Szeredi
0 siblings, 0 replies; 28+ messages in thread
From: Miklos Szeredi @ 2019-04-04 8:01 UTC (permalink / raw)
To: Al Viro
Cc: Christopher Lameter, Tobin C. Harding, Andrew Morton,
Roman Gushchin, Alexander Viro, Christoph Hellwig, Pekka Enberg,
David Rientjes, Joonsoo Kim, Matthew Wilcox, Miklos Szeredi,
Andreas Dilger, Waiman Long, Tycho Andersen, Theodore Ts'o,
Andi Kleen, David Chinner, Nick Piggin, Rik van Riel,
Hugh Dickins, linux-mm, linux-fsdevel, linux-kernel,
Linus Torvalds
On Wed, Apr 3, 2019 at 9:05 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> On Wed, Apr 03, 2019 at 07:24:54PM +0100, Al Viro wrote:
>
> > If by "how to do it right" you mean "expedit kicking out something with
> > non-zero refcount" - there's no way to do that. Nothing even remotely
> > sane.
> >
> > If you mean "kick out everything in this page with zero refcount" - that
> > can be done (see further in the thread).
> >
> > Look, dentries and inodes are really, really not relocatable. If they
> > can be evicted by memory pressure - sure, we can do that for a given
> > set (e.g. "everything in that page"). But that's it - if memory
> > pressure would _not_ get rid of that one, there's nothing to be done.
> > Again, all VM can do is to simulate shrinker hitting hard on given
> > bunch (rather than buggering the entire cache). If filesystem (or
> > something in VFS) says "it's busy", it bloody well _is_ busy and
> > won't be going away until it ceases to be such.
>
> FWIW, some theory: the only kind of long-term reference that can
> be killed off by memory pressure is that from child to parent.
> Anything else (e.g. an opened file, current directory, mountpoint,
> etc.) is out of limits - it either won't be going away until
> the thing is not pinned anymore (close, chdir, etc.) *or*
> it really shouldn't be ("VM wants this mountpoint dentry freed,
> so just dissolve the mount" is a bloody bad idea for obvious
> reasons).
Well, theoretically we could do two levels of references, where the
long term reference is stable and contains an rcu protected unstable
reference to the real object. In the likely case when only read-only
access to the object is needed (d_lookup) then the cost is an extra
dereference and the associated additional cache usage. If read-write
access is needed to object, then extra locking is needed to protect
against concurrent migration. So there's non-trivial cost in addition
to the added complexity, and I don't see it actually making sense in
practice. But maybe someone can expand this idea to something
practicable...
Thanks,
Miklos
^ permalink raw reply [flat|nested] 28+ messages in thread
* Re: [RFC PATCH v2 14/14] dcache: Implement object migration
2019-04-03 18:24 ` Al Viro
2019-04-03 19:05 ` Al Viro
@ 2019-04-04 15:46 ` Christopher Lameter
1 sibling, 0 replies; 28+ messages in thread
From: Christopher Lameter @ 2019-04-04 15:46 UTC (permalink / raw)
To: Al Viro
Cc: Tobin C. Harding, Andrew Morton, Roman Gushchin, Alexander Viro,
Christoph Hellwig, Pekka Enberg, David Rientjes, Joonsoo Kim,
Matthew Wilcox, Miklos Szeredi, Andreas Dilger, Waiman Long,
Tycho Andersen, Theodore Ts'o, Andi Kleen, David Chinner,
Nick Piggin, Rik van Riel, Hugh Dickins, linux-mm, linux-fsdevel,
linux-kernel, Linus Torvalds
On Wed, 3 Apr 2019, Al Viro wrote:
> > This is an RFC and we want to know how to do this right.
>
> If by "how to do it right" you mean "expedit kicking out something with
> non-zero refcount" - there's no way to do that. Nothing even remotely
> sane.
Sure we know that.
> If you mean "kick out everything in this page with zero refcount" - that
> can be done (see further in the thread).
Ok that would already be progress. If we can use this to liberate some
slab pages with just a few dentry object then it may be worthwhile.
> Look, dentries and inodes are really, really not relocatable. If they
> can be evicted by memory pressure - sure, we can do that for a given
> set (e.g. "everything in that page"). But that's it - if memory
> pressure would _not_ get rid of that one, there's nothing to be done.
> Again, all VM can do is to simulate shrinker hitting hard on given
> bunch (rather than buggering the entire cache). If filesystem (or
> something in VFS) says "it's busy", it bloody well _is_ busy and
> won't be going away until it ceases to be such.
Right. Thats why the patch attempted to check for these things to avoid
touching such objects.
^ permalink raw reply [flat|nested] 28+ messages in thread