* [PATCH v6 1/5] mm,page_alloc: Bail out earlier on -ENOMEM in alloc_contig_migrate_range
2021-03-19 13:19 [PATCH v6 0/5] Make alloc_contig_range handle Hugetlb pages Oscar Salvador
@ 2021-03-19 13:20 ` Oscar Salvador
2021-03-19 13:20 ` [PATCH v6 2/5] mm,compaction: Let isolate_migratepages_{range,block} return error codes Oscar Salvador
` (3 subsequent siblings)
4 siblings, 0 replies; 8+ messages in thread
From: Oscar Salvador @ 2021-03-19 13:20 UTC (permalink / raw)
To: Andrew Morton
Cc: Mike Kravetz, Vlastimil Babka, David Hildenbrand, Michal Hocko,
Muchun Song, linux-mm, linux-kernel, Oscar Salvador,
Michal Hocko
Currently, __alloc_contig_migrate_range can generate -EINTR, -ENOMEM or -EBUSY,
and report them down the chain.
The problem is that when migrate_pages() reports -ENOMEM, we keep going till we
exhaust all the try-attempts (5 at the moment) instead of bailing out.
migrate_pages() bails out right away on -ENOMEM because it is considered a fatal
error. Do the same here instead of keep going and retrying.
Note that this is not fixing a real issue, just a cosmetic change. Although we
can save some cycles by backing off ealier
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
---
mm/page_alloc.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cfc72873961d..a4f67063b85f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8481,7 +8481,7 @@ static int __alloc_contig_migrate_range(struct compact_control *cc,
}
tries = 0;
} else if (++tries == 5) {
- ret = ret < 0 ? ret : -EBUSY;
+ ret = -EBUSY;
break;
}
@@ -8491,6 +8491,12 @@ static int __alloc_contig_migrate_range(struct compact_control *cc,
ret = migrate_pages(&cc->migratepages, alloc_migration_target,
NULL, (unsigned long)&mtc, cc->mode, MR_CONTIG_RANGE);
+ /*
+ * On -ENOMEM, migrate_pages() bails out right away. It is pointless
+ * to retry again over this error, so do the same here.
+ */
+ if (ret == -ENOMEM)
+ break;
}
if (ret < 0) {
putback_movable_pages(&cc->migratepages);
--
2.16.3
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH v6 2/5] mm,compaction: Let isolate_migratepages_{range,block} return error codes
2021-03-19 13:19 [PATCH v6 0/5] Make alloc_contig_range handle Hugetlb pages Oscar Salvador
2021-03-19 13:20 ` [PATCH v6 1/5] mm,page_alloc: Bail out earlier on -ENOMEM in alloc_contig_migrate_range Oscar Salvador
@ 2021-03-19 13:20 ` Oscar Salvador
2021-03-23 10:49 ` Oscar Salvador
2021-03-19 13:20 ` [PATCH v6 3/5] mm: Make alloc_contig_range handle free hugetlb pages Oscar Salvador
` (2 subsequent siblings)
4 siblings, 1 reply; 8+ messages in thread
From: Oscar Salvador @ 2021-03-19 13:20 UTC (permalink / raw)
To: Andrew Morton
Cc: Mike Kravetz, Vlastimil Babka, David Hildenbrand, Michal Hocko,
Muchun Song, linux-mm, linux-kernel, Oscar Salvador
Currently, isolate_migratepages_{range,block} and their callers use
a pfn == 0 vs pfn != 0 scheme to let the caller know whether there was
any error during isolation.
This does not work as soon as we need to start reporting different error
codes and make sure we pass them down the chain, so they are properly
interpreted by functions like e.g: alloc_contig_range.
Let us rework isolate_migratepages_{range,block} so we can report error
codes.
Since isolate_migratepages_block will stop returning the next pfn to be
scanned, we reuse the cc->migrate_pfn field to keep track of that.
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/compaction.c | 53 ++++++++++++++++++++++++++---------------------------
mm/internal.h | 10 ++++++++--
mm/page_alloc.c | 7 +++----
3 files changed, 37 insertions(+), 33 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index e04f4476e68e..cd090a675321 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -787,15 +787,15 @@ static bool too_many_isolated(pg_data_t *pgdat)
*
* Isolate all pages that can be migrated from the range specified by
* [low_pfn, end_pfn). The range is expected to be within same pageblock.
- * Returns zero if there is a fatal signal pending, otherwise PFN of the
- * first page that was not scanned (which may be both less, equal to or more
- * than end_pfn).
+ * Returns errno, like -EAGAIN or -EINTR in case e.g signal pending or congestion,
+ * or 0.
+ * cc->migrate_pfn will contain the next pfn to scan (which may be both less,
+ * equal to or more that end_pfn).
*
* The pages are isolated on cc->migratepages list (not required to be empty),
- * and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field
- * is neither read nor updated.
- */
-static unsigned long
+ * and cc->nr_migratepages is updated accordingly.
+*/
+static int
isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
unsigned long end_pfn, isolate_mode_t isolate_mode)
{
@@ -810,6 +810,8 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
unsigned long next_skip_pfn = 0;
bool skip_updated = false;
+ cc->migrate_pfn = low_pfn;
+
/*
* Ensure that there are not too many pages isolated from the LRU
* list by either parallel reclaimers or compaction. If there are,
@@ -818,16 +820,16 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
while (unlikely(too_many_isolated(pgdat))) {
/* stop isolation if there are still pages not migrated */
if (cc->nr_migratepages)
- return 0;
+ return -EAGAIN;
/* async migration should just abort */
if (cc->mode == MIGRATE_ASYNC)
- return 0;
+ return -EAGAIN;
congestion_wait(BLK_RW_ASYNC, HZ/10);
if (fatal_signal_pending(current))
- return 0;
+ return -EINTR;
}
cond_resched();
@@ -1130,7 +1132,9 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
if (nr_isolated)
count_compact_events(COMPACTISOLATED, nr_isolated);
- return low_pfn;
+ cc->migrate_pfn = low_pfn;
+
+ return 0;
}
/**
@@ -1139,15 +1143,15 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
* @start_pfn: The first PFN to start isolating.
* @end_pfn: The one-past-last PFN.
*
- * Returns zero if isolation fails fatally due to e.g. pending signal.
- * Otherwise, function returns one-past-the-last PFN of isolated page
- * (which may be greater than end_pfn if end fell in a middle of a THP page).
+ * Returns errno, like -EAGAIN or -EINTR in case e.g signal pending or congestion,
+ * or 0.
*/
-unsigned long
+int
isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
unsigned long end_pfn)
{
unsigned long pfn, block_start_pfn, block_end_pfn;
+ int ret = 0;
/* Scan block by block. First and last block may be incomplete */
pfn = start_pfn;
@@ -1166,17 +1170,17 @@ isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
block_end_pfn, cc->zone))
continue;
- pfn = isolate_migratepages_block(cc, pfn, block_end_pfn,
- ISOLATE_UNEVICTABLE);
+ ret = isolate_migratepages_block(cc, pfn, block_end_pfn,
+ ISOLATE_UNEVICTABLE);
- if (!pfn)
+ if (ret)
break;
if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX)
break;
}
- return pfn;
+ return ret;
}
#endif /* CONFIG_COMPACTION || CONFIG_CMA */
@@ -1847,7 +1851,7 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc)
*/
for (; block_end_pfn <= cc->free_pfn;
fast_find_block = false,
- low_pfn = block_end_pfn,
+ cc->migrate_pfn = low_pfn = block_end_pfn,
block_start_pfn = block_end_pfn,
block_end_pfn += pageblock_nr_pages) {
@@ -1889,10 +1893,8 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc)
}
/* Perform the isolation */
- low_pfn = isolate_migratepages_block(cc, low_pfn,
- block_end_pfn, isolate_mode);
-
- if (!low_pfn)
+ if (isolate_migratepages_block(cc, low_pfn, block_end_pfn,
+ isolate_mode))
return ISOLATE_ABORT;
/*
@@ -1903,9 +1905,6 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc)
break;
}
- /* Record where migration scanner will be restarted. */
- cc->migrate_pfn = low_pfn;
-
return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE;
}
diff --git a/mm/internal.h b/mm/internal.h
index 1432feec62df..aedb9120ac16 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -225,7 +225,13 @@ struct compact_control {
unsigned int nr_freepages; /* Number of isolated free pages */
unsigned int nr_migratepages; /* Number of pages to migrate */
unsigned long free_pfn; /* isolate_freepages search base */
- unsigned long migrate_pfn; /* isolate_migratepages search base */
+ /*
+ * Acts as an in/out parameter to page isolation for migration.
+ * isolate_migratepages uses it as a search base.
+ * isolate_migratepages_block will update the value to the next pfn
+ * after the last isolated one.
+ */
+ unsigned long migrate_pfn;
unsigned long fast_start_pfn; /* a pfn to start linear scan from */
struct zone *zone;
unsigned long total_migrate_scanned;
@@ -261,7 +267,7 @@ struct capture_control {
unsigned long
isolate_freepages_range(struct compact_control *cc,
unsigned long start_pfn, unsigned long end_pfn);
-unsigned long
+int
isolate_migratepages_range(struct compact_control *cc,
unsigned long low_pfn, unsigned long end_pfn);
int find_suitable_fallback(struct free_area *area, unsigned int order,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a4f67063b85f..ce6a14a446a4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8474,11 +8474,10 @@ static int __alloc_contig_migrate_range(struct compact_control *cc,
if (list_empty(&cc->migratepages)) {
cc->nr_migratepages = 0;
- pfn = isolate_migratepages_range(cc, pfn, end);
- if (!pfn) {
- ret = -EINTR;
+ ret = isolate_migratepages_range(cc, pfn, end);
+ if (ret && ret != -EAGAIN)
break;
- }
+ pfn = cc->migrate_pfn;
tries = 0;
} else if (++tries == 5) {
ret = -EBUSY;
--
2.16.3
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH v6 2/5] mm,compaction: Let isolate_migratepages_{range,block} return error codes
2021-03-19 13:20 ` [PATCH v6 2/5] mm,compaction: Let isolate_migratepages_{range,block} return error codes Oscar Salvador
@ 2021-03-23 10:49 ` Oscar Salvador
0 siblings, 0 replies; 8+ messages in thread
From: Oscar Salvador @ 2021-03-23 10:49 UTC (permalink / raw)
To: Andrew Morton
Cc: Mike Kravetz, Vlastimil Babka, David Hildenbrand, Michal Hocko,
Muchun Song, linux-mm, linux-kernel
On Fri, Mar 19, 2021 at 02:20:01PM +0100, Oscar Salvador wrote:
> Currently, isolate_migratepages_{range,block} and their callers use
> a pfn == 0 vs pfn != 0 scheme to let the caller know whether there was
> any error during isolation.
> This does not work as soon as we need to start reporting different error
> codes and make sure we pass them down the chain, so they are properly
> interpreted by functions like e.g: alloc_contig_range.
>
> Let us rework isolate_migratepages_{range,block} so we can report error
> codes.
> Since isolate_migratepages_block will stop returning the next pfn to be
> scanned, we reuse the cc->migrate_pfn field to keep track of that.
>
> Signed-off-by: Oscar Salvador <osalvador@suse.de>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
Hi Andrew,
I realized a missed place wrt. error handling.
could you squash this on top?
diff --git a/mm/compaction.c b/mm/compaction.c
index cd090a675321..9b989fc3168d 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -809,6 +809,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
bool skip_on_failure = false;
unsigned long next_skip_pfn = 0;
bool skip_updated = false;
+ int ret = 0;
cc->migrate_pfn = low_pfn;
@@ -877,8 +878,8 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
if (fatal_signal_pending(current)) {
cc->contended = true;
+ ret = -EINTR;
- low_pfn = 0;
goto fatal_pending;
}
@@ -1134,7 +1135,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
cc->migrate_pfn = low_pfn;
- return 0;
+ return ret;
}
Thanks a lot
--
Oscar Salvador
SUSE L3
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH v6 3/5] mm: Make alloc_contig_range handle free hugetlb pages
2021-03-19 13:19 [PATCH v6 0/5] Make alloc_contig_range handle Hugetlb pages Oscar Salvador
2021-03-19 13:20 ` [PATCH v6 1/5] mm,page_alloc: Bail out earlier on -ENOMEM in alloc_contig_migrate_range Oscar Salvador
2021-03-19 13:20 ` [PATCH v6 2/5] mm,compaction: Let isolate_migratepages_{range,block} return error codes Oscar Salvador
@ 2021-03-19 13:20 ` Oscar Salvador
2021-03-19 13:20 ` [PATCH v6 4/5] mm: Make alloc_contig_range handle in-use " Oscar Salvador
2021-03-19 13:20 ` [PATCH v6 5/5] mm,page_alloc: Drop unnecessary checks from pfn_range_valid_contig Oscar Salvador
4 siblings, 0 replies; 8+ messages in thread
From: Oscar Salvador @ 2021-03-19 13:20 UTC (permalink / raw)
To: Andrew Morton
Cc: Mike Kravetz, Vlastimil Babka, David Hildenbrand, Michal Hocko,
Muchun Song, linux-mm, linux-kernel, Oscar Salvador,
Michal Hocko
alloc_contig_range will fail if it ever sees a HugeTLB page within the
range we are trying to allocate, even when that page is free and can be
easily reallocated.
This has proved to be problematic for some users of alloc_contic_range,
e.g: CMA and virtio-mem, where those would fail the call even when those
pages lay in ZONE_MOVABLE and are free.
We can do better by trying to replace such page.
Free hugepages are tricky to handle so as to no userspace application
notices disruption, we need to replace the current free hugepage with
a new one.
In order to do that, a new function called alloc_and_dissolve_huge_page
is introduced.
This function will first try to get a new fresh hugepage, and if it
succeeds, it will replace the old one in the free hugepage pool.
The free page replacement is done under hugetlb_lock, so no external
user of hugetlb will notice the change. There is one tricky case when
page's refcount is 0 because it is in the process of being released.
A missing PageHugeFreed bit will tell us that freeing is in flight so
we retry after dropping the hugetlb_lock. The race window should be
small and the next retry should make a forward progress.
E.g:
CPU0 CPU1
__free_huge_page() isolate_or_dissolve_huge_page
PageHuge() == T
alloc_and_dissolve_huge_page
alloc_fresh_huge_page()
spin_lock(hugetlb_lock)
// PageHuge() && !PageHugeFreed &&
// !PageCount()
spin_unlock(hugetlb_lock)
spin_lock(hugetlb_lock)
1) update_and_free_page
PageHuge() == F
__free_pages()
2) enqueue_huge_page
SetPageHugeFreed()
spin_unlock(&hugetlb_lock)
spin_lock(hugetlb_lock)
1) PageHuge() == F (freed by case#1 from CPU0)
2) PageHuge() == T
PageHugeFreed() == T
- proceed with replacing the page
In the case above we retry as the window race is quite small and we have high
chances to succeed next time.
With regard to the allocation, we restrict it to the node the page belongs
to with __GFP_THISNODE, meaning we do not fallback on other node's zones.
Note that gigantic hugetlb pages are fenced off since there is a cyclic
dependency between them and alloc_contig_range.
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
---
include/linux/hugetlb.h | 6 +++
mm/compaction.c | 37 ++++++++++++++--
mm/hugetlb.c | 109 +++++++++++++++++++++++++++++++++++++++++++++++-
3 files changed, 147 insertions(+), 5 deletions(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index cccd1aab69dd..bcff86ca616f 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -583,6 +583,7 @@ struct huge_bootmem_page {
struct hstate *hstate;
};
+int isolate_or_dissolve_huge_page(struct page *page);
struct page *alloc_huge_page(struct vm_area_struct *vma,
unsigned long addr, int avoid_reserve);
struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid,
@@ -865,6 +866,11 @@ static inline void huge_ptep_modify_prot_commit(struct vm_area_struct *vma,
#else /* CONFIG_HUGETLB_PAGE */
struct hstate {};
+static inline int isolate_or_dissolve_huge_page(struct page *page)
+{
+ return -ENOMEM;
+}
+
static inline struct page *alloc_huge_page(struct vm_area_struct *vma,
unsigned long addr,
int avoid_reserve)
diff --git a/mm/compaction.c b/mm/compaction.c
index cd090a675321..3b26c5c6c931 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -788,7 +788,7 @@ static bool too_many_isolated(pg_data_t *pgdat)
* Isolate all pages that can be migrated from the range specified by
* [low_pfn, end_pfn). The range is expected to be within same pageblock.
* Returns errno, like -EAGAIN or -EINTR in case e.g signal pending or congestion,
- * or 0.
+ * -ENOMEM in case we could not allocate a page, or 0.
* cc->migrate_pfn will contain the next pfn to scan (which may be both less,
* equal to or more that end_pfn).
*
@@ -809,6 +809,8 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
bool skip_on_failure = false;
unsigned long next_skip_pfn = 0;
bool skip_updated = false;
+ bool fatal_error = false;
+ int ret = 0;
cc->migrate_pfn = low_pfn;
@@ -906,6 +908,32 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
valid_page = page;
}
+ if (PageHuge(page) && cc->alloc_contig) {
+ ret = isolate_or_dissolve_huge_page(page);
+
+ /*
+ * Fail isolation in case isolate_or_dissolve_huge_page
+ * reports an error. In case of -ENOMEM, abort right away.
+ */
+ if (ret < 0) {
+ /*
+ * Do not report -EBUSY down the chain.
+ */
+ if (ret == -ENOMEM)
+ fatal_error = true;
+ else
+ ret = 0;
+ goto isolate_fail;
+ }
+
+ /*
+ * Ok, the hugepage was dissolved. Now these pages are
+ * Buddy and cannot be re-allocated because they are
+ * isolated. Fall-through as the check below handles
+ * Buddy pages.
+ */
+ }
+
/*
* Skip if free. We read page order here without zone lock
* which is generally unsafe, but the race window is small and
@@ -1091,6 +1119,9 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
*/
next_skip_pfn += 1UL << cc->order;
}
+
+ if (fatal_error)
+ break;
}
/*
@@ -1134,7 +1165,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
cc->migrate_pfn = low_pfn;
- return 0;
+ return ret;
}
/**
@@ -1144,7 +1175,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
* @end_pfn: The one-past-last PFN.
*
* Returns errno, like -EAGAIN or -EINTR in case e.g signal pending or congestion,
- * or 0.
+ * -ENOMEM in case we could not allocate a page, or 0.
*/
int
isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 5b1ab1f427c5..3194c1bd9e32 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1035,13 +1035,18 @@ static bool vma_has_reserves(struct vm_area_struct *vma, long chg)
return false;
}
+static void __enqueue_huge_page(struct list_head *list, struct page *page)
+{
+ list_move(&page->lru, list);
+ SetHPageFreed(page);
+}
+
static void enqueue_huge_page(struct hstate *h, struct page *page)
{
int nid = page_to_nid(page);
- list_move(&page->lru, &h->hugepage_freelists[nid]);
+ __enqueue_huge_page(&h->hugepage_freelists[nid], page);
h->free_huge_pages++;
h->free_huge_pages_node[nid]++;
- SetHPageFreed(page);
}
static struct page *dequeue_huge_page_node_exact(struct hstate *h, int nid)
@@ -2245,6 +2250,106 @@ static void restore_reserve_on_error(struct hstate *h,
}
}
+/*
+ * alloc_and_dissolve_huge_page - Allocate a new page and dissolve the old one
+ * @h: struct hstate old page belongs to
+ * @old_page: Old page to dissolve
+ * Returns 0 on success, otherwise negated error.
+ */
+
+static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page)
+{
+ gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
+ int nid = page_to_nid(old_page);
+ struct page *new_page;
+ int ret = 0;
+
+ /*
+ * Before dissolving the page, we need to allocate a new one,
+ * so the pool remains stable.
+ */
+ new_page = alloc_fresh_huge_page(h, gfp_mask, nid, NULL, NULL);
+ if (!new_page)
+ return -ENOMEM;
+
+ /*
+ * Pages got from Buddy are self-refcounted, but free hugepages
+ * need to have a refcount of 0.
+ */
+ page_ref_dec(new_page);
+retry:
+ spin_lock(&hugetlb_lock);
+ if (!PageHuge(old_page)) {
+ /*
+ * Freed from under us. Drop new_page too.
+ */
+ update_and_free_page(h, new_page);
+ goto unlock;
+ } else if (page_count(old_page)) {
+ /*
+ * Someone has grabbed the page, fail for now.
+ */
+ ret = -EBUSY;
+ update_and_free_page(h, new_page);
+ goto unlock;
+ } else if (!HPageFreed(old_page)) {
+ /*
+ * Page's refcount is 0 but it has not been enqueued in the
+ * freelist yet. Race window is small, so we can succed here if
+ * we retry.
+ */
+ spin_unlock(&hugetlb_lock);
+ cond_resched();
+ goto retry;
+ } else {
+ /*
+ * Ok, old_page is still a genuine free hugepage. Replace it
+ * with the new one.
+ */
+ list_del(&old_page->lru);
+ update_and_free_page(h, old_page);
+ /*
+ * h->free_huge_pages{_node} counters do not need to be updated.
+ */
+ __enqueue_huge_page(&h->hugepage_freelists[nid], new_page);
+ }
+unlock:
+ spin_unlock(&hugetlb_lock);
+
+ return ret;
+}
+
+int isolate_or_dissolve_huge_page(struct page *page)
+{
+ struct hstate *h;
+ struct page *head;
+
+ /*
+ * The page might have been dissolved from under our feet, so make sure
+ * to carefully check the state under the lock.
+ * Return success when racing as if we dissolved the page ourselves.
+ */
+ spin_lock(&hugetlb_lock);
+ if (PageHuge(page)) {
+ head = compound_head(page);
+ h = page_hstate(head);
+ } else {
+ spin_unlock(&hugetlb_lock);
+ return 0;
+ }
+ spin_unlock(&hugetlb_lock);
+
+ /*
+ * Fence off gigantic pages as there is a cyclic dependency between
+ * alloc_contig_range and them. Return -ENOME as this has the effect
+ * of bailing out right away without further retrying.
+ */
+ if (hstate_is_gigantic(h))
+ return -ENOMEM;
+
+ return alloc_and_dissolve_huge_page(h, head);
+}
+
struct page *alloc_huge_page(struct vm_area_struct *vma,
unsigned long addr, int avoid_reserve)
{
--
2.16.3
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH v6 4/5] mm: Make alloc_contig_range handle in-use hugetlb pages
2021-03-19 13:19 [PATCH v6 0/5] Make alloc_contig_range handle Hugetlb pages Oscar Salvador
` (2 preceding siblings ...)
2021-03-19 13:20 ` [PATCH v6 3/5] mm: Make alloc_contig_range handle free hugetlb pages Oscar Salvador
@ 2021-03-19 13:20 ` Oscar Salvador
2021-03-19 13:20 ` [PATCH v6 5/5] mm,page_alloc: Drop unnecessary checks from pfn_range_valid_contig Oscar Salvador
4 siblings, 0 replies; 8+ messages in thread
From: Oscar Salvador @ 2021-03-19 13:20 UTC (permalink / raw)
To: Andrew Morton
Cc: Mike Kravetz, Vlastimil Babka, David Hildenbrand, Michal Hocko,
Muchun Song, linux-mm, linux-kernel, Oscar Salvador,
Michal Hocko
alloc_contig_range() will fail if it finds a HugeTLB page within the range,
without a chance to handle them. Since HugeTLB pages can be migrated as any
LRU or Movable page, it does not make sense to bail out without trying.
Enable the interface to recognize in-use HugeTLB pages so we can migrate
them, and have much better chances to succeed the call.
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
---
include/linux/hugetlb.h | 5 +++--
mm/compaction.c | 12 +++++++++++-
mm/hugetlb.c | 22 ++++++++++++++++------
mm/vmscan.c | 5 +++--
4 files changed, 33 insertions(+), 11 deletions(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index bcff86ca616f..a37b4ce86e58 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -583,7 +583,7 @@ struct huge_bootmem_page {
struct hstate *hstate;
};
-int isolate_or_dissolve_huge_page(struct page *page);
+int isolate_or_dissolve_huge_page(struct page *page, struct list_head *list);
struct page *alloc_huge_page(struct vm_area_struct *vma,
unsigned long addr, int avoid_reserve);
struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid,
@@ -866,7 +866,8 @@ static inline void huge_ptep_modify_prot_commit(struct vm_area_struct *vma,
#else /* CONFIG_HUGETLB_PAGE */
struct hstate {};
-static inline int isolate_or_dissolve_huge_page(struct page *page)
+static inline int isolate_or_dissolve_huge_page(struct page *page,
+ struct list_head *list)
{
return -ENOMEM;
}
diff --git a/mm/compaction.c b/mm/compaction.c
index 3b26c5c6c931..4143d1984a21 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -909,7 +909,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
}
if (PageHuge(page) && cc->alloc_contig) {
- ret = isolate_or_dissolve_huge_page(page);
+ ret = isolate_or_dissolve_huge_page(page, &cc->migratepages);
/*
* Fail isolation in case isolate_or_dissolve_huge_page
@@ -926,6 +926,15 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
goto isolate_fail;
}
+ if (PageHuge(page)) {
+ /*
+ * Hugepage was successfully isolated and placed
+ * on the cc->migratepages list.
+ */
+ low_pfn += compound_nr(page) - 1;
+ goto isolate_success_no_list;
+ }
+
/*
* Ok, the hugepage was dissolved. Now these pages are
* Buddy and cannot be re-allocated because they are
@@ -1067,6 +1076,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
isolate_success:
list_add(&page->lru, &cc->migratepages);
+isolate_success_no_list:
cc->nr_migratepages += compound_nr(page);
nr_isolated += compound_nr(page);
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3194c1bd9e32..85e4bedbd5ac 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2257,7 +2257,8 @@ static void restore_reserve_on_error(struct hstate *h,
* Returns 0 on success, otherwise negated error.
*/
-static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page)
+static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page,
+ struct list_head *list)
{
gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
int nid = page_to_nid(old_page);
@@ -2287,11 +2288,14 @@ static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page)
goto unlock;
} else if (page_count(old_page)) {
/*
- * Someone has grabbed the page, fail for now.
+ * Someone has grabbed the page, try to isolate it here.
+ * Fail with -EBUSY if not possible.
*/
- ret = -EBUSY;
update_and_free_page(h, new_page);
- goto unlock;
+ spin_unlock(&hugetlb_lock);
+ if (!isolate_huge_page(old_page, list))
+ ret = -EBUSY;
+ return ret;
} else if (!HPageFreed(old_page)) {
/*
* Page's refcount is 0 but it has not been enqueued in the
@@ -2319,10 +2323,11 @@ static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page)
return ret;
}
-int isolate_or_dissolve_huge_page(struct page *page)
+int isolate_or_dissolve_huge_page(struct page *page, struct list_head *list)
{
struct hstate *h;
struct page *head;
+ int ret = -EBUSY;
/*
* The page might have been dissolved from under our feet, so make sure
@@ -2347,7 +2352,12 @@ int isolate_or_dissolve_huge_page(struct page *page)
if (hstate_is_gigantic(h))
return -ENOMEM;
- return alloc_and_dissolve_huge_page(h, head);
+ if (page_count(head) && isolate_huge_page(head, list))
+ ret = 0;
+ else if (!page_count(head))
+ ret = alloc_and_dissolve_huge_page(h, head, list);
+
+ return ret;
}
struct page *alloc_huge_page(struct vm_area_struct *vma,
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 562e87cbd7a1..42aaef30633e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1507,8 +1507,9 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
LIST_HEAD(clean_pages);
list_for_each_entry_safe(page, next, page_list, lru) {
- if (page_is_file_lru(page) && !PageDirty(page) &&
- !__PageMovable(page) && !PageUnevictable(page)) {
+ if (!PageHuge(page) && page_is_file_lru(page) &&
+ !PageDirty(page) && !__PageMovable(page) &&
+ !PageUnevictable(page)) {
ClearPageActive(page);
list_move(&page->lru, &clean_pages);
}
--
2.16.3
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH v6 5/5] mm,page_alloc: Drop unnecessary checks from pfn_range_valid_contig
2021-03-19 13:19 [PATCH v6 0/5] Make alloc_contig_range handle Hugetlb pages Oscar Salvador
` (3 preceding siblings ...)
2021-03-19 13:20 ` [PATCH v6 4/5] mm: Make alloc_contig_range handle in-use " Oscar Salvador
@ 2021-03-19 13:20 ` Oscar Salvador
2021-03-22 15:44 ` Michal Hocko
4 siblings, 1 reply; 8+ messages in thread
From: Oscar Salvador @ 2021-03-19 13:20 UTC (permalink / raw)
To: Andrew Morton
Cc: Mike Kravetz, Vlastimil Babka, David Hildenbrand, Michal Hocko,
Muchun Song, linux-mm, linux-kernel, Oscar Salvador
pfn_range_valid_contig() bails out when it finds an in-use page or a
hugetlb page, among other things.
We can drop the in-use page check since __alloc_contig_pages can migrate
away those pages, and the hugetlb page check can go too since
isolate_migratepages_range is now capable of dealing with hugetlb pages.
Either way, those checks are racy so let the end function handle it
when the time comes.
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Suggested-by: David Hildenbrand <david@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
---
mm/page_alloc.c | 6 ------
1 file changed, 6 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ce6a14a446a4..516302b280de 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8685,12 +8685,6 @@ static bool pfn_range_valid_contig(struct zone *z, unsigned long start_pfn,
if (PageReserved(page))
return false;
-
- if (page_count(page) > 0)
- return false;
-
- if (PageHuge(page))
- return false;
}
return true;
}
--
2.16.3
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH v6 5/5] mm,page_alloc: Drop unnecessary checks from pfn_range_valid_contig
2021-03-19 13:20 ` [PATCH v6 5/5] mm,page_alloc: Drop unnecessary checks from pfn_range_valid_contig Oscar Salvador
@ 2021-03-22 15:44 ` Michal Hocko
0 siblings, 0 replies; 8+ messages in thread
From: Michal Hocko @ 2021-03-22 15:44 UTC (permalink / raw)
To: Oscar Salvador
Cc: Andrew Morton, Mike Kravetz, Vlastimil Babka, David Hildenbrand,
Muchun Song, linux-mm, linux-kernel
On Fri 19-03-21 14:20:04, Oscar Salvador wrote:
> pfn_range_valid_contig() bails out when it finds an in-use page or a
> hugetlb page, among other things.
> We can drop the in-use page check since __alloc_contig_pages can migrate
> away those pages, and the hugetlb page check can go too since
> isolate_migratepages_range is now capable of dealing with hugetlb pages.
> Either way, those checks are racy so let the end function handle it
> when the time comes.
>
> Signed-off-by: Oscar Salvador <osalvador@suse.de>
> Suggested-by: David Hildenbrand <david@redhat.com>
> Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
> ---
> mm/page_alloc.c | 6 ------
> 1 file changed, 6 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index ce6a14a446a4..516302b280de 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8685,12 +8685,6 @@ static bool pfn_range_valid_contig(struct zone *z, unsigned long start_pfn,
>
> if (PageReserved(page))
> return false;
> -
> - if (page_count(page) > 0)
> - return false;
> -
> - if (PageHuge(page))
> - return false;
> }
> return true;
> }
> --
> 2.16.3
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 8+ messages in thread