[v4,2/3] mm: memcg/slab: Create a new set of kmalloc-cg-<n> caches
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Message ID 20210505200610.13943-3-longman@redhat.com
State In Next
Commit 4d57437a3d3c5429dd030923ef00b1e35e0c6827
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  • mm: memcg/slab: Fix objcg pointer array handling problem
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Commit Message

Waiman Long May 5, 2021, 8:06 p.m. UTC
There are currently two problems in the way the objcg pointer array
(memcg_data) in the page structure is being allocated and freed.

On its allocation, it is possible that the allocated objcg pointer
array comes from the same slab that requires memory accounting. If this
happens, the slab will never become empty again as there is at least
one object left (the obj_cgroup array) in the slab.

When it is freed, the objcg pointer array object may be the last one
in its slab and hence causes kfree() to be called again. With the
right workload, the slab cache may be set up in a way that allows the
recursive kfree() calling loop to nest deep enough to cause a kernel
stack overflow and panic the system.

One way to solve this problem is to split the kmalloc-<n> caches
(KMALLOC_NORMAL) into two separate sets - a new set of kmalloc-<n>
(KMALLOC_NORMAL) caches for unaccounted objects only and a new set of
kmalloc-cg-<n> (KMALLOC_CGROUP) caches for accounted objects only. All
the other caches can still allow a mix of accounted and unaccounted
objects.

With this change, all the objcg pointer array objects will come from
KMALLOC_NORMAL caches which won't have their objcg pointer arrays. So
both the recursive kfree() problem and non-freeable slab problem are
gone.

Since both the KMALLOC_NORMAL and KMALLOC_CGROUP caches no longer have
mixed accounted and unaccounted objects, this will slightly reduce the
number of objcg pointer arrays that need to be allocated and save a bit
of memory. On the other hand, creating a new set of kmalloc caches does
have the effect of reducing cache utilization. So it is properly a wash.

The new KMALLOC_CGROUP is added between KMALLOC_NORMAL and
KMALLOC_RECLAIM so that the first for loop in create_kmalloc_caches()
will include the newly added caches without change.

Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
---
 include/linux/slab.h | 41 ++++++++++++++++++++++++++++++++---------
 mm/slab_common.c     | 25 +++++++++++++++++--------
 2 files changed, 49 insertions(+), 17 deletions(-)

Comments

Roman Gushchin May 5, 2021, 8:37 p.m. UTC | #1
On Wed, May 05, 2021 at 04:06:09PM -0400, Waiman Long wrote:
> There are currently two problems in the way the objcg pointer array
> (memcg_data) in the page structure is being allocated and freed.
> 
> On its allocation, it is possible that the allocated objcg pointer
> array comes from the same slab that requires memory accounting. If this
> happens, the slab will never become empty again as there is at least
> one object left (the obj_cgroup array) in the slab.
> 
> When it is freed, the objcg pointer array object may be the last one
> in its slab and hence causes kfree() to be called again. With the
> right workload, the slab cache may be set up in a way that allows the
> recursive kfree() calling loop to nest deep enough to cause a kernel
> stack overflow and panic the system.
> 
> One way to solve this problem is to split the kmalloc-<n> caches
> (KMALLOC_NORMAL) into two separate sets - a new set of kmalloc-<n>
> (KMALLOC_NORMAL) caches for unaccounted objects only and a new set of
> kmalloc-cg-<n> (KMALLOC_CGROUP) caches for accounted objects only. All
> the other caches can still allow a mix of accounted and unaccounted
> objects.
> 
> With this change, all the objcg pointer array objects will come from
> KMALLOC_NORMAL caches which won't have their objcg pointer arrays. So
> both the recursive kfree() problem and non-freeable slab problem are
> gone.
> 
> Since both the KMALLOC_NORMAL and KMALLOC_CGROUP caches no longer have
> mixed accounted and unaccounted objects, this will slightly reduce the
> number of objcg pointer arrays that need to be allocated and save a bit
> of memory. On the other hand, creating a new set of kmalloc caches does
> have the effect of reducing cache utilization. So it is properly a wash.
> 
> The new KMALLOC_CGROUP is added between KMALLOC_NORMAL and
> KMALLOC_RECLAIM so that the first for loop in create_kmalloc_caches()
> will include the newly added caches without change.
> 
> Suggested-by: Vlastimil Babka <vbabka@suse.cz>
> Signed-off-by: Waiman Long <longman@redhat.com>
> Reviewed-by: Shakeel Butt <shakeelb@google.com>

Acked-by: Roman Gushchin <guro@fb.com>
Vlastimil Babka May 5, 2021, 9:41 p.m. UTC | #2
On 5/5/21 10:06 PM, Waiman Long wrote:
> There are currently two problems in the way the objcg pointer array
> (memcg_data) in the page structure is being allocated and freed.
> 
> On its allocation, it is possible that the allocated objcg pointer
> array comes from the same slab that requires memory accounting. If this
> happens, the slab will never become empty again as there is at least
> one object left (the obj_cgroup array) in the slab.
> 
> When it is freed, the objcg pointer array object may be the last one
> in its slab and hence causes kfree() to be called again. With the
> right workload, the slab cache may be set up in a way that allows the
> recursive kfree() calling loop to nest deep enough to cause a kernel
> stack overflow and panic the system.
> 
> One way to solve this problem is to split the kmalloc-<n> caches
> (KMALLOC_NORMAL) into two separate sets - a new set of kmalloc-<n>
> (KMALLOC_NORMAL) caches for unaccounted objects only and a new set of
> kmalloc-cg-<n> (KMALLOC_CGROUP) caches for accounted objects only. All
> the other caches can still allow a mix of accounted and unaccounted
> objects.
> 
> With this change, all the objcg pointer array objects will come from
> KMALLOC_NORMAL caches which won't have their objcg pointer arrays. So
> both the recursive kfree() problem and non-freeable slab problem are
> gone.
> 
> Since both the KMALLOC_NORMAL and KMALLOC_CGROUP caches no longer have
> mixed accounted and unaccounted objects, this will slightly reduce the
> number of objcg pointer arrays that need to be allocated and save a bit
> of memory. On the other hand, creating a new set of kmalloc caches does
> have the effect of reducing cache utilization. So it is properly a wash.
> 
> The new KMALLOC_CGROUP is added between KMALLOC_NORMAL and
> KMALLOC_RECLAIM so that the first for loop in create_kmalloc_caches()
> will include the newly added caches without change.
> 
> Suggested-by: Vlastimil Babka <vbabka@suse.cz>
> Signed-off-by: Waiman Long <longman@redhat.com>
> Reviewed-by: Shakeel Butt <shakeelb@google.com>

A last nitpick: the new caches -cg should perhaps not be created when
cgroup_memory_nokmem == true because kmemcg was disabled by the respective boot
param.
Waiman Long May 5, 2021, 11:19 p.m. UTC | #3
On 5/5/21 5:41 PM, Vlastimil Babka wrote:
> On 5/5/21 10:06 PM, Waiman Long wrote:
>> There are currently two problems in the way the objcg pointer array
>> (memcg_data) in the page structure is being allocated and freed.
>>
>> On its allocation, it is possible that the allocated objcg pointer
>> array comes from the same slab that requires memory accounting. If this
>> happens, the slab will never become empty again as there is at least
>> one object left (the obj_cgroup array) in the slab.
>>
>> When it is freed, the objcg pointer array object may be the last one
>> in its slab and hence causes kfree() to be called again. With the
>> right workload, the slab cache may be set up in a way that allows the
>> recursive kfree() calling loop to nest deep enough to cause a kernel
>> stack overflow and panic the system.
>>
>> One way to solve this problem is to split the kmalloc-<n> caches
>> (KMALLOC_NORMAL) into two separate sets - a new set of kmalloc-<n>
>> (KMALLOC_NORMAL) caches for unaccounted objects only and a new set of
>> kmalloc-cg-<n> (KMALLOC_CGROUP) caches for accounted objects only. All
>> the other caches can still allow a mix of accounted and unaccounted
>> objects.
>>
>> With this change, all the objcg pointer array objects will come from
>> KMALLOC_NORMAL caches which won't have their objcg pointer arrays. So
>> both the recursive kfree() problem and non-freeable slab problem are
>> gone.
>>
>> Since both the KMALLOC_NORMAL and KMALLOC_CGROUP caches no longer have
>> mixed accounted and unaccounted objects, this will slightly reduce the
>> number of objcg pointer arrays that need to be allocated and save a bit
>> of memory. On the other hand, creating a new set of kmalloc caches does
>> have the effect of reducing cache utilization. So it is properly a wash.
>>
>> The new KMALLOC_CGROUP is added between KMALLOC_NORMAL and
>> KMALLOC_RECLAIM so that the first for loop in create_kmalloc_caches()
>> will include the newly added caches without change.
>>
>> Suggested-by: Vlastimil Babka <vbabka@suse.cz>
>> Signed-off-by: Waiman Long <longman@redhat.com>
>> Reviewed-by: Shakeel Butt <shakeelb@google.com>
> A last nitpick: the new caches -cg should perhaps not be created when
> cgroup_memory_nokmem == true because kmemcg was disabled by the respective boot
> param.
>
It is a nice to have feature. However, the nokmem kernel parameter isn't 
used that often. The cgroup_memory_nokmem variable is private to 
memcontrol.c and is not directly accessible. I will take a look on that, 
but it will be a follow-on patch. I am not planning to change the 
current patchset unless there are other issues coming up.

Cheers,
Longman
Vlastimil Babka May 6, 2021, 4 p.m. UTC | #4
On 5/5/21 10:06 PM, Waiman Long wrote:
> There are currently two problems in the way the objcg pointer array
> (memcg_data) in the page structure is being allocated and freed.
> 
> On its allocation, it is possible that the allocated objcg pointer
> array comes from the same slab that requires memory accounting. If this
> happens, the slab will never become empty again as there is at least
> one object left (the obj_cgroup array) in the slab.
> 
> When it is freed, the objcg pointer array object may be the last one
> in its slab and hence causes kfree() to be called again. With the
> right workload, the slab cache may be set up in a way that allows the
> recursive kfree() calling loop to nest deep enough to cause a kernel
> stack overflow and panic the system.
> 
> One way to solve this problem is to split the kmalloc-<n> caches
> (KMALLOC_NORMAL) into two separate sets - a new set of kmalloc-<n>
> (KMALLOC_NORMAL) caches for unaccounted objects only and a new set of
> kmalloc-cg-<n> (KMALLOC_CGROUP) caches for accounted objects only. All
> the other caches can still allow a mix of accounted and unaccounted
> objects.
> 
> With this change, all the objcg pointer array objects will come from
> KMALLOC_NORMAL caches which won't have their objcg pointer arrays. So
> both the recursive kfree() problem and non-freeable slab problem are
> gone.
> 
> Since both the KMALLOC_NORMAL and KMALLOC_CGROUP caches no longer have
> mixed accounted and unaccounted objects, this will slightly reduce the
> number of objcg pointer arrays that need to be allocated and save a bit
> of memory. On the other hand, creating a new set of kmalloc caches does
> have the effect of reducing cache utilization. So it is properly a wash.
> 
> The new KMALLOC_CGROUP is added between KMALLOC_NORMAL and
> KMALLOC_RECLAIM so that the first for loop in create_kmalloc_caches()
> will include the newly added caches without change.
> 
> Suggested-by: Vlastimil Babka <vbabka@suse.cz>
> Signed-off-by: Waiman Long <longman@redhat.com>
> Reviewed-by: Shakeel Butt <shakeelb@google.com>

Reviewed-by: Vlastimil Babka <vbabka@suse.cz>

I still believe the cgroup.memory=nokmem parameter should be respected,
otherwise the caches are not only created, but also used. I offer this followup
for squashing into your patch if you and Andrew agree:

----8<----
From c87378d437d9a59b8757033485431b4721c74173 Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <vbabka@suse.cz>
Date: Thu, 6 May 2021 17:53:21 +0200
Subject: [PATCH] mm: memcg/slab: don't create kmalloc-cg caches with
 cgroup.memory=nokmem

The caches should not be created when kmemcg is disabled on boot, otherwise
they are also filled by kmalloc(__GFP_ACCOUNT) allocations. When booted with
cgroup.memory=nokmem, link the kmalloc_caches[KMALLOC_CGROUP] entries to
KMALLOC_NORMAL entries instead.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/internal.h    | 5 +++++
 mm/memcontrol.c  | 2 +-
 mm/slab_common.c | 9 +++++++--
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index ef5f336f59bd..b2d60b3403c7 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -135,6 +135,11 @@ extern void putback_lru_page(struct page *page);
  */
 extern pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address);
 
+/*
+ * in mm/memcontrol.c:
+ */
+extern bool cgroup_memory_nokmem;
+
 /*
  * in mm/page_alloc.c
  */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5e3b4f23b830..b9ec01f2b4f6 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -83,7 +83,7 @@ DEFINE_PER_CPU(struct mem_cgroup *, int_active_memcg);
 static bool cgroup_memory_nosocket;
 
 /* Kernel memory accounting disabled? */
-static bool cgroup_memory_nokmem;
+bool cgroup_memory_nokmem;
 
 /* Whether the swap controller is active */
 #ifdef CONFIG_MEMCG_SWAP
diff --git a/mm/slab_common.c b/mm/slab_common.c
index bbaf41a7c77e..363f90215401 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -832,10 +832,15 @@ void __init setup_kmalloc_cache_index_table(void)
 static void __init
 new_kmalloc_cache(int idx, enum kmalloc_cache_type type, slab_flags_t flags)
 {
-	if (type == KMALLOC_RECLAIM)
+	if (type == KMALLOC_RECLAIM) {
 		flags |= SLAB_RECLAIM_ACCOUNT;
-	else if (IS_ENABLED(CONFIG_MEMCG_KMEM) && (type == KMALLOC_CGROUP))
+	} else if (IS_ENABLED(CONFIG_MEMCG_KMEM) && (type == KMALLOC_CGROUP)) {
+		if (cgroup_memory_nokmem) {
+			kmalloc_caches[type][idx] = kmalloc_caches[KMALLOC_NORMAL][idx];
+			return;
+		}
 		flags |= SLAB_ACCOUNT;
+	}
 
 	kmalloc_caches[type][idx] = create_kmalloc_cache(
 					kmalloc_info[idx].name[type],
Shakeel Butt May 6, 2021, 4:07 p.m. UTC | #5
On Thu, May 6, 2021 at 9:00 AM Vlastimil Babka <vbabka@suse.cz> wrote:
>
>
> On 5/5/21 10:06 PM, Waiman Long wrote:
> > There are currently two problems in the way the objcg pointer array
> > (memcg_data) in the page structure is being allocated and freed.
> >
> > On its allocation, it is possible that the allocated objcg pointer
> > array comes from the same slab that requires memory accounting. If this
> > happens, the slab will never become empty again as there is at least
> > one object left (the obj_cgroup array) in the slab.
> >
> > When it is freed, the objcg pointer array object may be the last one
> > in its slab and hence causes kfree() to be called again. With the
> > right workload, the slab cache may be set up in a way that allows the
> > recursive kfree() calling loop to nest deep enough to cause a kernel
> > stack overflow and panic the system.
> >
> > One way to solve this problem is to split the kmalloc-<n> caches
> > (KMALLOC_NORMAL) into two separate sets - a new set of kmalloc-<n>
> > (KMALLOC_NORMAL) caches for unaccounted objects only and a new set of
> > kmalloc-cg-<n> (KMALLOC_CGROUP) caches for accounted objects only. All
> > the other caches can still allow a mix of accounted and unaccounted
> > objects.
> >
> > With this change, all the objcg pointer array objects will come from
> > KMALLOC_NORMAL caches which won't have their objcg pointer arrays. So
> > both the recursive kfree() problem and non-freeable slab problem are
> > gone.
> >
> > Since both the KMALLOC_NORMAL and KMALLOC_CGROUP caches no longer have
> > mixed accounted and unaccounted objects, this will slightly reduce the
> > number of objcg pointer arrays that need to be allocated and save a bit
> > of memory. On the other hand, creating a new set of kmalloc caches does
> > have the effect of reducing cache utilization. So it is properly a wash.
> >
> > The new KMALLOC_CGROUP is added between KMALLOC_NORMAL and
> > KMALLOC_RECLAIM so that the first for loop in create_kmalloc_caches()
> > will include the newly added caches without change.
> >
> > Suggested-by: Vlastimil Babka <vbabka@suse.cz>
> > Signed-off-by: Waiman Long <longman@redhat.com>
> > Reviewed-by: Shakeel Butt <shakeelb@google.com>
>
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
>
> I still believe the cgroup.memory=nokmem parameter should be respected,
> otherwise the caches are not only created, but also used. I offer this followup
> for squashing into your patch if you and Andrew agree:
>
> ----8<----
> From c87378d437d9a59b8757033485431b4721c74173 Mon Sep 17 00:00:00 2001
> From: Vlastimil Babka <vbabka@suse.cz>
> Date: Thu, 6 May 2021 17:53:21 +0200
> Subject: [PATCH] mm: memcg/slab: don't create kmalloc-cg caches with
>  cgroup.memory=nokmem
>
> The caches should not be created when kmemcg is disabled on boot, otherwise
> they are also filled by kmalloc(__GFP_ACCOUNT) allocations. When booted with
> cgroup.memory=nokmem, link the kmalloc_caches[KMALLOC_CGROUP] entries to
> KMALLOC_NORMAL entries instead.
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Yes this makes sense:

Reviewed-by: Shakeel Butt <shakeelb@google.com>
Roman Gushchin May 6, 2021, 7:30 p.m. UTC | #6
On Thu, May 06, 2021 at 06:00:16PM +0200, Vlastimil Babka wrote:
> 
> On 5/5/21 10:06 PM, Waiman Long wrote:
> > There are currently two problems in the way the objcg pointer array
> > (memcg_data) in the page structure is being allocated and freed.
> > 
> > On its allocation, it is possible that the allocated objcg pointer
> > array comes from the same slab that requires memory accounting. If this
> > happens, the slab will never become empty again as there is at least
> > one object left (the obj_cgroup array) in the slab.
> > 
> > When it is freed, the objcg pointer array object may be the last one
> > in its slab and hence causes kfree() to be called again. With the
> > right workload, the slab cache may be set up in a way that allows the
> > recursive kfree() calling loop to nest deep enough to cause a kernel
> > stack overflow and panic the system.
> > 
> > One way to solve this problem is to split the kmalloc-<n> caches
> > (KMALLOC_NORMAL) into two separate sets - a new set of kmalloc-<n>
> > (KMALLOC_NORMAL) caches for unaccounted objects only and a new set of
> > kmalloc-cg-<n> (KMALLOC_CGROUP) caches for accounted objects only. All
> > the other caches can still allow a mix of accounted and unaccounted
> > objects.
> > 
> > With this change, all the objcg pointer array objects will come from
> > KMALLOC_NORMAL caches which won't have their objcg pointer arrays. So
> > both the recursive kfree() problem and non-freeable slab problem are
> > gone.
> > 
> > Since both the KMALLOC_NORMAL and KMALLOC_CGROUP caches no longer have
> > mixed accounted and unaccounted objects, this will slightly reduce the
> > number of objcg pointer arrays that need to be allocated and save a bit
> > of memory. On the other hand, creating a new set of kmalloc caches does
> > have the effect of reducing cache utilization. So it is properly a wash.
> > 
> > The new KMALLOC_CGROUP is added between KMALLOC_NORMAL and
> > KMALLOC_RECLAIM so that the first for loop in create_kmalloc_caches()
> > will include the newly added caches without change.
> > 
> > Suggested-by: Vlastimil Babka <vbabka@suse.cz>
> > Signed-off-by: Waiman Long <longman@redhat.com>
> > Reviewed-by: Shakeel Butt <shakeelb@google.com>
> 
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
> 
> I still believe the cgroup.memory=nokmem parameter should be respected,
> otherwise the caches are not only created, but also used.

+1

> I offer this followup
> for squashing into your patch if you and Andrew agree:
> 
> ----8<----
> From c87378d437d9a59b8757033485431b4721c74173 Mon Sep 17 00:00:00 2001
> From: Vlastimil Babka <vbabka@suse.cz>
> Date: Thu, 6 May 2021 17:53:21 +0200
> Subject: [PATCH] mm: memcg/slab: don't create kmalloc-cg caches with
>  cgroup.memory=nokmem
> 
> The caches should not be created when kmemcg is disabled on boot, otherwise
> they are also filled by kmalloc(__GFP_ACCOUNT) allocations. When booted with
> cgroup.memory=nokmem, link the kmalloc_caches[KMALLOC_CGROUP] entries to
> KMALLOC_NORMAL entries instead.
> 
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Acked-by: Roman Gushchin <guro@fb.com>

Thanks!
Waiman Long May 7, 2021, 6:45 p.m. UTC | #7
On 5/6/21 12:00 PM, Vlastimil Babka wrote:
> On 5/5/21 10:06 PM, Waiman Long wrote:
>> There are currently two problems in the way the objcg pointer array
>> (memcg_data) in the page structure is being allocated and freed.
>>
>> On its allocation, it is possible that the allocated objcg pointer
>> array comes from the same slab that requires memory accounting. If this
>> happens, the slab will never become empty again as there is at least
>> one object left (the obj_cgroup array) in the slab.
>>
>> When it is freed, the objcg pointer array object may be the last one
>> in its slab and hence causes kfree() to be called again. With the
>> right workload, the slab cache may be set up in a way that allows the
>> recursive kfree() calling loop to nest deep enough to cause a kernel
>> stack overflow and panic the system.
>>
>> One way to solve this problem is to split the kmalloc-<n> caches
>> (KMALLOC_NORMAL) into two separate sets - a new set of kmalloc-<n>
>> (KMALLOC_NORMAL) caches for unaccounted objects only and a new set of
>> kmalloc-cg-<n> (KMALLOC_CGROUP) caches for accounted objects only. All
>> the other caches can still allow a mix of accounted and unaccounted
>> objects.
>>
>> With this change, all the objcg pointer array objects will come from
>> KMALLOC_NORMAL caches which won't have their objcg pointer arrays. So
>> both the recursive kfree() problem and non-freeable slab problem are
>> gone.
>>
>> Since both the KMALLOC_NORMAL and KMALLOC_CGROUP caches no longer have
>> mixed accounted and unaccounted objects, this will slightly reduce the
>> number of objcg pointer arrays that need to be allocated and save a bit
>> of memory. On the other hand, creating a new set of kmalloc caches does
>> have the effect of reducing cache utilization. So it is properly a wash.
>>
>> The new KMALLOC_CGROUP is added between KMALLOC_NORMAL and
>> KMALLOC_RECLAIM so that the first for loop in create_kmalloc_caches()
>> will include the newly added caches without change.
>>
>> Suggested-by: Vlastimil Babka <vbabka@suse.cz>
>> Signed-off-by: Waiman Long <longman@redhat.com>
>> Reviewed-by: Shakeel Butt <shakeelb@google.com>
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
>
> I still believe the cgroup.memory=nokmem parameter should be respected,
> otherwise the caches are not only created, but also used. I offer this followup
> for squashing into your patch if you and Andrew agree:
>
> ----8<----
>  From c87378d437d9a59b8757033485431b4721c74173 Mon Sep 17 00:00:00 2001
> From: Vlastimil Babka <vbabka@suse.cz>
> Date: Thu, 6 May 2021 17:53:21 +0200
> Subject: [PATCH] mm: memcg/slab: don't create kmalloc-cg caches with
>   cgroup.memory=nokmem
>
> The caches should not be created when kmemcg is disabled on boot, otherwise
> they are also filled by kmalloc(__GFP_ACCOUNT) allocations. When booted with
> cgroup.memory=nokmem, link the kmalloc_caches[KMALLOC_CGROUP] entries to
> KMALLOC_NORMAL entries instead.
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> ---
>   mm/internal.h    | 5 +++++
>   mm/memcontrol.c  | 2 +-
>   mm/slab_common.c | 9 +++++++--
>   3 files changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/mm/internal.h b/mm/internal.h
> index ef5f336f59bd..b2d60b3403c7 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -135,6 +135,11 @@ extern void putback_lru_page(struct page *page);
>    */
>   extern pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address);
>   
> +/*
> + * in mm/memcontrol.c:
> + */
> +extern bool cgroup_memory_nokmem;
> +
>   /*
>    * in mm/page_alloc.c
>    */
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 5e3b4f23b830..b9ec01f2b4f6 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -83,7 +83,7 @@ DEFINE_PER_CPU(struct mem_cgroup *, int_active_memcg);
>   static bool cgroup_memory_nosocket;
>   
>   /* Kernel memory accounting disabled? */
> -static bool cgroup_memory_nokmem;
> +bool cgroup_memory_nokmem;
>   
>   /* Whether the swap controller is active */
>   #ifdef CONFIG_MEMCG_SWAP
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index bbaf41a7c77e..363f90215401 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -832,10 +832,15 @@ void __init setup_kmalloc_cache_index_table(void)
>   static void __init
>   new_kmalloc_cache(int idx, enum kmalloc_cache_type type, slab_flags_t flags)
>   {
> -	if (type == KMALLOC_RECLAIM)
> +	if (type == KMALLOC_RECLAIM) {
>   		flags |= SLAB_RECLAIM_ACCOUNT;
> -	else if (IS_ENABLED(CONFIG_MEMCG_KMEM) && (type == KMALLOC_CGROUP))
> +	} else if (IS_ENABLED(CONFIG_MEMCG_KMEM) && (type == KMALLOC_CGROUP)) {
> +		if (cgroup_memory_nokmem) {
> +			kmalloc_caches[type][idx] = kmalloc_caches[KMALLOC_NORMAL][idx];
> +			return;
> +		}
>   		flags |= SLAB_ACCOUNT;
> +	}
>   
>   	kmalloc_caches[type][idx] = create_kmalloc_cache(
>   					kmalloc_info[idx].name[type],

Thanks, the patch looks good to me.

Acked-by: Waiman Long <longman@redhat.com>

Cheers,
Longman

Patch
diff mbox series

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 0c97d788762c..a51cad5f561c 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -305,12 +305,23 @@  static inline void __check_heap_object(const void *ptr, unsigned long n,
 /*
  * Whenever changing this, take care of that kmalloc_type() and
  * create_kmalloc_caches() still work as intended.
+ *
+ * KMALLOC_NORMAL can contain only unaccounted objects whereas KMALLOC_CGROUP
+ * is for accounted but unreclaimable and non-dma objects. All the other
+ * kmem caches can have both accounted and unaccounted objects.
  */
 enum kmalloc_cache_type {
 	KMALLOC_NORMAL = 0,
+#ifdef CONFIG_MEMCG_KMEM
+	KMALLOC_CGROUP,
+#else
+	KMALLOC_CGROUP = KMALLOC_NORMAL,
+#endif
 	KMALLOC_RECLAIM,
 #ifdef CONFIG_ZONE_DMA
 	KMALLOC_DMA,
+#else
+	KMALLOC_DMA = KMALLOC_NORMAL,
 #endif
 	NR_KMALLOC_TYPES
 };
@@ -319,24 +330,36 @@  enum kmalloc_cache_type {
 extern struct kmem_cache *
 kmalloc_caches[NR_KMALLOC_TYPES][KMALLOC_SHIFT_HIGH + 1];
 
+/*
+ * Define gfp bits that should not be set for KMALLOC_NORMAL.
+ */
+#define KMALLOC_NOT_NORMAL_BITS					\
+	(__GFP_RECLAIMABLE |					\
+	(IS_ENABLED(CONFIG_ZONE_DMA)   ? __GFP_DMA : 0) |	\
+	(IS_ENABLED(CONFIG_MEMCG_KMEM) ? __GFP_ACCOUNT : 0))
+
 static __always_inline enum kmalloc_cache_type kmalloc_type(gfp_t flags)
 {
-#ifdef CONFIG_ZONE_DMA
 	/*
 	 * The most common case is KMALLOC_NORMAL, so test for it
-	 * with a single branch for both flags.
+	 * with a single branch for all the relevant flags.
 	 */
-	if (likely((flags & (__GFP_DMA | __GFP_RECLAIMABLE)) == 0))
+	if (likely((flags & KMALLOC_NOT_NORMAL_BITS) == 0))
 		return KMALLOC_NORMAL;
 
 	/*
-	 * At least one of the flags has to be set. If both are, __GFP_DMA
-	 * is more important.
+	 * At least one of the flags has to be set. Their priorities in
+	 * decreasing order are:
+	 *  1) __GFP_DMA
+	 *  2) __GFP_RECLAIMABLE
+	 *  3) __GFP_ACCOUNT
 	 */
-	return flags & __GFP_DMA ? KMALLOC_DMA : KMALLOC_RECLAIM;
-#else
-	return flags & __GFP_RECLAIMABLE ? KMALLOC_RECLAIM : KMALLOC_NORMAL;
-#endif
+	if (IS_ENABLED(CONFIG_ZONE_DMA) && (flags & __GFP_DMA))
+		return KMALLOC_DMA;
+	if (!IS_ENABLED(CONFIG_MEMCG_KMEM) || (flags & __GFP_RECLAIMABLE))
+		return KMALLOC_RECLAIM;
+	else
+		return KMALLOC_CGROUP;
 }
 
 /*
diff --git a/mm/slab_common.c b/mm/slab_common.c
index f8833d3e5d47..bbaf41a7c77e 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -727,21 +727,25 @@  struct kmem_cache *kmalloc_slab(size_t size, gfp_t flags)
 }
 
 #ifdef CONFIG_ZONE_DMA
-#define INIT_KMALLOC_INFO(__size, __short_size)			\
-{								\
-	.name[KMALLOC_NORMAL]  = "kmalloc-" #__short_size,	\
-	.name[KMALLOC_RECLAIM] = "kmalloc-rcl-" #__short_size,	\
-	.name[KMALLOC_DMA]     = "dma-kmalloc-" #__short_size,	\
-	.size = __size,						\
-}
+#define KMALLOC_DMA_NAME(sz)	.name[KMALLOC_DMA] = "dma-kmalloc-" #sz,
+#else
+#define KMALLOC_DMA_NAME(sz)
+#endif
+
+#ifdef CONFIG_MEMCG_KMEM
+#define KMALLOC_CGROUP_NAME(sz)	.name[KMALLOC_CGROUP] = "kmalloc-cg-" #sz,
 #else
+#define KMALLOC_CGROUP_NAME(sz)
+#endif
+
 #define INIT_KMALLOC_INFO(__size, __short_size)			\
 {								\
 	.name[KMALLOC_NORMAL]  = "kmalloc-" #__short_size,	\
 	.name[KMALLOC_RECLAIM] = "kmalloc-rcl-" #__short_size,	\
+	KMALLOC_CGROUP_NAME(__short_size)			\
+	KMALLOC_DMA_NAME(__short_size)				\
 	.size = __size,						\
 }
-#endif
 
 /*
  * kmalloc_info[] is to make slub_debug=,kmalloc-xx option work at boot time.
@@ -830,6 +834,8 @@  new_kmalloc_cache(int idx, enum kmalloc_cache_type type, slab_flags_t flags)
 {
 	if (type == KMALLOC_RECLAIM)
 		flags |= SLAB_RECLAIM_ACCOUNT;
+	else if (IS_ENABLED(CONFIG_MEMCG_KMEM) && (type == KMALLOC_CGROUP))
+		flags |= SLAB_ACCOUNT;
 
 	kmalloc_caches[type][idx] = create_kmalloc_cache(
 					kmalloc_info[idx].name[type],
@@ -847,6 +853,9 @@  void __init create_kmalloc_caches(slab_flags_t flags)
 	int i;
 	enum kmalloc_cache_type type;
 
+	/*
+	 * Including KMALLOC_CGROUP if CONFIG_MEMCG_KMEM defined
+	 */
 	for (type = KMALLOC_NORMAL; type <= KMALLOC_RECLAIM; type++) {
 		for (i = KMALLOC_SHIFT_LOW; i <= KMALLOC_SHIFT_HIGH; i++) {
 			if (!kmalloc_caches[type][i])