From: Zi Yan <[email protected]>
Hi all,
This patchset enables >0 order folio memory compaction, which is one of
the prerequisitions for large folio support[1]. It is on top of
mm-everything-2024-01-18-22-21.
I am aware of that split free pages is necessary for folio
migration in compaction, since if >0 order free pages are never split
and no order-0 free page is scanned, compaction will end prematurely due
to migration returns -ENOMEM. Free page split becomes a must instead of
an optimization.
Some applications from vm-scalability show different performance trends
on default LRU and CONFIG_LRU_GEN from patch 1 (split folio during compaction),
to patch 2 (folio migration during compaction), to patch 3 (folio
migration during compaction with free page split). I am looking into it.
lkp ncompare results (with >5% delta) for default LRU and CONFIG_LRU_GEN are
shown at the bottom (on a 8-CPU (Intel Xeon E5-2650 v4 @ 2.20GHz) 16G VM).
Changelog
===
From V1 [2]:
1. Used folio_test_large() instead of folio_order() > 0. (per Matthew
Wilcox)
2. Fixed code rebase error. (per Baolin Wang)
3. Used list_split_init() instead of list_split(). (per Ryan Boberts)
4. Added free_pages_prepare_fpi_none() to avoid duplicate free page code
in compaction_free().
5. Dropped source page order sorting patch.
From RFC [1]:
1. Enabled >0 order folio compaction in the first patch by splitting all
to-be-migrated folios. (per Huang, Ying)
2. Stopped isolating compound pages with order greater than cc->order
to avoid wasting effort, since cc->order gives a hint that no free pages
with order greater than it exist, thus migrating the compound pages will fail.
(per Baolin Wang)
3. Retained the folio check within lru lock. (per Baolin Wang)
4. Made isolate_freepages_block() generate order-sorted multi lists.
(per Johannes Weiner)
Overview
===
To support >0 order folio compaction, the patchset changes how free pages used
for migration are kept during compaction. Free pages used to be split into
order-0 pages that are post allocation processed (i.e., PageBuddy flag cleared,
page order stored in page->private is zeroed, and page reference is set to 1).
Now all free pages are kept in a MAX_ORDER+1 array of page lists based
on their order without post allocation process. When migrate_pages() asks for
a new page, one of the free pages, based on the requested page order, is
then processed and given out.
Feel free to give comments and ask questions.
Thanks.
[1] https://lore.kernel.org/linux-mm/[email protected]/
[2] https://lore.kernel.org/linux-mm/[email protected]/
vm-scalability results on CONFIG_LRU_GEN
===
=========================================================================================
compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
gcc-13/defconfig/debian/300s/qemu-vm/small-allocs/vm-scalability
commit:
6.7.0-rc4+
6.7.0-rc4-split-folio-in-compaction+
6.7.0-rc4-folio-migration-in-compaction+
6.7.0-rc4-folio-migration-free-page-split+
6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
---------------- --------------------------- --------------------------- ---------------------------
%stddev %change %stddev %change %stddev %change %stddev
\ | \ | \ | \
2024326 +35.5% 2743772 ± 41% +364.0% 9392198 ± 35% +31.0% 2651634 vm-scalability.throughput
=========================================================================================
compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
gcc-13/defconfig/debian/300s/qemu-vm/small-allocs-mt/vm-scalability
commit:
6.7.0-rc4+
6.7.0-rc4-split-folio-in-compaction+
6.7.0-rc4-folio-migration-in-compaction+
6.7.0-rc4-folio-migration-free-page-split+
6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
---------------- --------------------------- --------------------------- ---------------------------
%stddev %change %stddev %change %stddev %change %stddev
\ | \ | \ | \
1450189 +0.9% 1463418 +30.4% 1891610 ± 22% +0.3% 1454100 vm-scalability.throughput
=========================================================================================
compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
gcc-13/defconfig/debian/300s/qemu-vm/mmap-xread-seq-mt/vm-scalability
commit:
6.7.0-rc4+
6.7.0-rc4-split-folio-in-compaction+
6.7.0-rc4-folio-migration-in-compaction+
6.7.0-rc4-folio-migration-free-page-split+
6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
---------------- --------------------------- --------------------------- ---------------------------
%stddev %change %stddev %change %stddev %change %stddev
\ | \ | \ | \
14428848 ± 27% -51.7% 6963308 ± 73% +13.5% 16372621 +11.2% 16046511 vm-scalability.throughput
=========================================================================================
compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
gcc-13/defconfig/debian/300s/qemu-vm/mmap-pread-seq/vm-scalability
commit:
6.7.0-rc4+
6.7.0-rc4-split-folio-in-compaction+
6.7.0-rc4-folio-migration-in-compaction+
6.7.0-rc4-folio-migration-free-page-split+
6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
---------------- --------------------------- --------------------------- ---------------------------
%stddev %change %stddev %change %stddev %change %stddev
\ | \ | \ | \
13569502 ± 24% -45.9% 7340064 ± 59% +12.3% 15240531 +10.4% 14983705 vm-scalability.throughput
=========================================================================================
compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
gcc-13/defconfig/debian/300s/qemu-vm/mmap-pread-seq-mt/vm-scalability
commit:
6.7.0-rc4+
6.7.0-rc4-split-folio-in-compaction+
6.7.0-rc4-folio-migration-in-compaction+
6.7.0-rc4-folio-migration-free-page-split+
6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
---------------- --------------------------- --------------------------- ---------------------------
%stddev %change %stddev %change %stddev %change %stddev
\ | \ | \ | \
13305823 ± 24% -45.1% 7299664 ± 56% +12.5% 14974725 +10.4% 14695963 vm-scalability.throughput
=========================================================================================
compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
gcc-13/defconfig/debian/300s/qemu-vm/lru-file-readtwice/vm-scalability
commit:
6.7.0-rc4+
6.7.0-rc4-split-folio-in-compaction+
6.7.0-rc4-folio-migration-in-compaction+
6.7.0-rc4-folio-migration-free-page-split+
6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
---------------- --------------------------- --------------------------- ---------------------------
%stddev %change %stddev %change %stddev %change %stddev
\ | \ | \ | \
13244376 ± 28% +54.2% 20425838 ± 23% -4.4% 12660113 ± 3% -9.0% 12045809 ± 3% vm-scalability.throughput
=========================================================================================
compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
gcc-13/defconfig/debian/300s/qemu-vm/lru-file-mmap-read/vm-scalability
commit:
6.7.0-rc4+
6.7.0-rc4-split-folio-in-compaction+
6.7.0-rc4-folio-migration-in-compaction+
6.7.0-rc4-folio-migration-free-page-split+
6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
---------------- --------------------------- --------------------------- ---------------------------
%stddev %change %stddev %change %stddev %change %stddev
\ | \ | \ | \
7021425 ± 11% -20.9% 5556751 ± 19% +14.8% 8057811 ± 3% +9.4% 7678613 ± 4% vm-scalability.throughput
=========================================================================================
compiler/kconfig/rootfs/runtime/size/tbox_group/test/testcase:
gcc-13/defconfig/debian/300s/256G/qemu-vm/msync/vm-scalability
commit:
6.7.0-rc4+
6.7.0-rc4-split-folio-in-compaction+
6.7.0-rc4-folio-migration-in-compaction+
6.7.0-rc4-folio-migration-free-page-split+
6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
---------------- --------------------------- --------------------------- ---------------------------
%stddev %change %stddev %change %stddev %change %stddev
\ | \ | \ | \
1208994 ±137% +263.5% 4394683 ± 49% -49.4% 611204 ± 6% -48.1% 627937 ± 13% vm-scalability.throughput
vm-scalability results on default LRU (with -no-mglru suffix)
===
=========================================================================================
compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
gcc-13/defconfig/debian/300s/qemu-vm/lru-file-readtwice/vm-scalability
commit:
6.7.0-rc4-no-mglru+
6.7.0-rc4-split-folio-in-compaction-no-mglru+
6.7.0-rc4-folio-migration-in-compaction-no-mglru+
6.7.0-rc4-folio-migration-free-page-split-no-mglru+
6.7.0-rc4-no-mgl 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
---------------- --------------------------- --------------------------- ---------------------------
%stddev %change %stddev %change %stddev %change %stddev
\ | \ | \ | \
8412072 ± 3% +32.1% 11114537 ± 41% +3.5% 8703491 ± 3% +1.5% 8536343 ± 3% vm-scalability.throughput
=========================================================================================
compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
gcc-13/defconfig/debian/300s/qemu-vm/lru-file-mmap-read/vm-scalability
commit:
6.7.0-rc4-no-mglru+
6.7.0-rc4-split-folio-in-compaction-no-mglru+
6.7.0-rc4-folio-migration-in-compaction-no-mglru+
6.7.0-rc4-folio-migration-free-page-split-no-mglru+
6.7.0-rc4-no-mgl 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
---------------- --------------------------- --------------------------- ---------------------------
%stddev %change %stddev %change %stddev %change %stddev
\ | \ | \ | \
7095358 +10.8% 7863635 ± 16% +5.5% 7484110 +1.5% 7200666 ± 4% vm-scalability.throughput
Zi Yan (3):
mm/compaction: enable compacting >0 order folios.
mm/compaction: add support for >0 order folio memory compaction.
mm/compaction: optimize >0 order folio compaction with free page
split.
mm/compaction.c | 218 ++++++++++++++++++++++++++++++++++--------------
mm/internal.h | 9 +-
mm/page_alloc.c | 6 ++
3 files changed, 169 insertions(+), 64 deletions(-)
--
2.43.0
From: Zi Yan <[email protected]>
migrate_pages() supports >0 order folio migration and during compaction,
even if compaction_alloc() cannot provide >0 order free pages,
migrate_pages() can split the source page and try to migrate the base pages
from the split. It can be a baseline and start point for adding support for
compacting >0 order folios.
Suggested-by: Huang Ying <[email protected]>
Signed-off-by: Zi Yan <[email protected]>
---
mm/compaction.c | 43 +++++++++++++++++++++++++++++++++++--------
1 file changed, 35 insertions(+), 8 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 27ada42924d5..61389540e1f1 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -816,6 +816,21 @@ static bool too_many_isolated(struct compact_control *cc)
return too_many;
}
+/*
+ * 1. if the page order is larger than or equal to target_order (i.e.,
+ * cc->order and when it is not -1 for global compaction), skip it since
+ * target_order already indicates no free page with larger than target_order
+ * exists and later migrating it will most likely fail;
+ *
+ * 2. compacting > pageblock_order pages does not improve memory fragmentation,
+ * skip them;
+ */
+static bool skip_isolation_on_order(int order, int target_order)
+{
+ return (target_order != -1 && order >= target_order) ||
+ order >= pageblock_order;
+}
+
/**
* isolate_migratepages_block() - isolate all migrate-able pages within
* a single pageblock
@@ -1009,7 +1024,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
/*
* Regardless of being on LRU, compound pages such as THP and
* hugetlbfs are not to be compacted unless we are attempting
- * an allocation much larger than the huge page size (eg CMA).
+ * an allocation larger than the compound page size.
* We can potentially save a lot of iterations if we skip them
* at once. The check is racy, but we can consider only valid
* values and the only danger is skipping too much.
@@ -1017,11 +1032,18 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
if (PageCompound(page) && !cc->alloc_contig) {
const unsigned int order = compound_order(page);
- if (likely(order <= MAX_PAGE_ORDER)) {
- low_pfn += (1UL << order) - 1;
- nr_scanned += (1UL << order) - 1;
+ /*
+ * Skip based on page order and compaction target order
+ * and skip hugetlbfs pages.
+ */
+ if (skip_isolation_on_order(order, cc->order) ||
+ PageHuge(page)) {
+ if (order <= MAX_PAGE_ORDER) {
+ low_pfn += (1UL << order) - 1;
+ nr_scanned += (1UL << order) - 1;
+ }
+ goto isolate_fail;
}
- goto isolate_fail;
}
/*
@@ -1146,10 +1168,11 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
}
/*
- * folio become large since the non-locked check,
- * and it's on LRU.
+ * Check LRU folio order under the lock
*/
- if (unlikely(folio_test_large(folio) && !cc->alloc_contig)) {
+ if (unlikely(skip_isolation_on_order(folio_order(folio),
+ cc->order) &&
+ !cc->alloc_contig)) {
low_pfn += folio_nr_pages(folio) - 1;
nr_scanned += folio_nr_pages(folio) - 1;
folio_set_lru(folio);
@@ -1767,6 +1790,10 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data)
struct compact_control *cc = (struct compact_control *)data;
struct folio *dst;
+ /* this makes migrate_pages() split the source page and retry */
+ if (folio_test_large(src) > 0)
+ return NULL;
+
if (list_empty(&cc->freepages)) {
isolate_freepages(cc);
--
2.43.0
From: Zi Yan <[email protected]>
During migration in a memory compaction, free pages are placed in an array
of page lists based on their order. But the desired free page order (i.e.,
the order of a source page) might not be always present, thus leading to
migration failures and premature compaction termination. Split a high
order free pages when source migration page has a lower order to increase
migration successful rate.
Note: merging free pages when a migration fails and a lower order free
page is returned via compaction_free() is possible, but there is too much
work. Since the free pages are not buddy pages, it is hard to identify
these free pages using existing PFN-based page merging algorithm.
Signed-off-by: Zi Yan <[email protected]>
---
mm/compaction.c | 37 ++++++++++++++++++++++++++++++++++++-
1 file changed, 36 insertions(+), 1 deletion(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 11f9898e39da..052c82481d64 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1812,9 +1812,43 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data)
struct compact_control *cc = (struct compact_control *)data;
struct folio *dst;
int order = folio_order(src);
+ bool has_isolated_pages = false;
+again:
if (!cc->freepages[order].nr_pages) {
- isolate_freepages(cc);
+ int i;
+
+ for (i = order + 1; i < NR_PAGE_ORDERS; i++) {
+ if (cc->freepages[i].nr_pages) {
+ struct page *freepage =
+ list_first_entry(&cc->freepages[i].pages,
+ struct page, lru);
+
+ int start_order = i;
+ unsigned long size = 1 << start_order;
+
+ list_del(&freepage->lru);
+ cc->freepages[i].nr_pages--;
+
+ while (start_order > order) {
+ start_order--;
+ size >>= 1;
+
+ list_add(&freepage[size].lru,
+ &cc->freepages[start_order].pages);
+ cc->freepages[start_order].nr_pages++;
+ set_page_private(&freepage[size], start_order);
+ }
+ dst = (struct folio *)freepage;
+ goto done;
+ }
+ }
+ if (!has_isolated_pages) {
+ isolate_freepages(cc);
+ has_isolated_pages = true;
+ goto again;
+ }
+
if (!cc->freepages[order].nr_pages)
return NULL;
}
@@ -1822,6 +1856,7 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data)
dst = list_first_entry(&cc->freepages[order].pages, struct folio, lru);
cc->freepages[order].nr_pages--;
list_del(&dst->lru);
+done:
post_alloc_hook(&dst->page, order, __GFP_MOVABLE);
if (order)
prep_compound_page(&dst->page, order);
--
2.43.0
From: Zi Yan <[email protected]>
Before last commit, memory compaction only migrates order-0 folios and
skips >0 order folios. Last commit splits all >0 order folios during
compaction. This commit migrates >0 order folios during compaction by
keeping isolated free pages at their original size without splitting them
into order-0 pages and using them directly during migration process.
What is different from the prior implementation:
1. All isolated free pages are kept in a NR_PAGE_ORDERS array of page
lists, where each page list stores free pages in the same order.
2. All free pages are not post_alloc_hook() processed nor buddy pages,
although their orders are stored in first page's private like buddy
pages.
3. During migration, in new page allocation time (i.e., in
compaction_alloc()), free pages are then processed by post_alloc_hook().
When migration fails and a new page is returned (i.e., in
compaction_free()), free pages are restored by reversing the
post_alloc_hook() operations using newly added
free_pages_prepare_fpi_none().
Step 3 is done for a latter optimization that splitting and/or merging free
pages during compaction becomes easier.
Note: without splitting free pages, compaction can end prematurely due to
migration will return -ENOMEM even if there is free pages. This happens
when no order-0 free page exist and compaction_alloc() return NULL.
Signed-off-by: Zi Yan <[email protected]>
---
mm/compaction.c | 148 +++++++++++++++++++++++++++++-------------------
mm/internal.h | 9 ++-
mm/page_alloc.c | 6 ++
3 files changed, 103 insertions(+), 60 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 61389540e1f1..11f9898e39da 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -66,45 +66,67 @@ static inline void count_compact_events(enum vm_event_item item, long delta)
#define COMPACTION_HPAGE_ORDER (PMD_SHIFT - PAGE_SHIFT)
#endif
-static unsigned long release_freepages(struct list_head *freelist)
+static void init_page_list(struct page_list *p)
{
- struct page *page, *next;
- unsigned long high_pfn = 0;
-
- list_for_each_entry_safe(page, next, freelist, lru) {
- unsigned long pfn = page_to_pfn(page);
- list_del(&page->lru);
- __free_page(page);
- if (pfn > high_pfn)
- high_pfn = pfn;
- }
-
- return high_pfn;
+ INIT_LIST_HEAD(&p->pages);
+ p->nr_pages = 0;
}
-static void split_map_pages(struct list_head *list)
+static void split_map_pages(struct page_list *freepages)
{
- unsigned int i, order, nr_pages;
+ unsigned int i, order, total_nr_pages;
struct page *page, *next;
LIST_HEAD(tmp_list);
- list_for_each_entry_safe(page, next, list, lru) {
- list_del(&page->lru);
+ for (order = 0; order < NR_PAGE_ORDERS; order++) {
+ total_nr_pages = freepages[order].nr_pages * (1 << order);
+ freepages[order].nr_pages = 0;
+
+ list_for_each_entry_safe(page, next, &freepages[order].pages, lru) {
+ unsigned int nr_pages;
+
+ list_del(&page->lru);
- order = page_private(page);
- nr_pages = 1 << order;
+ nr_pages = 1 << order;
- post_alloc_hook(page, order, __GFP_MOVABLE);
- if (order)
- split_page(page, order);
+ post_alloc_hook(page, order, __GFP_MOVABLE);
+ if (order)
+ split_page(page, order);
- for (i = 0; i < nr_pages; i++) {
- list_add(&page->lru, &tmp_list);
- page++;
+ for (i = 0; i < nr_pages; i++) {
+ list_add(&page->lru, &tmp_list);
+ page++;
+ }
}
+ freepages[0].nr_pages += total_nr_pages;
+ list_splice_init(&tmp_list, &freepages[0].pages);
}
+}
- list_splice(&tmp_list, list);
+static unsigned long release_free_list(struct page_list *freepages)
+{
+ int order;
+ unsigned long high_pfn = 0;
+
+ for (order = 0; order < NR_PAGE_ORDERS; order++) {
+ struct page *page, *next;
+
+ list_for_each_entry_safe(page, next, &freepages[order].pages, lru) {
+ unsigned long pfn = page_to_pfn(page);
+
+ list_del(&page->lru);
+ /*
+ * Convert free pages into post allocation pages, so
+ * that we can free them via __free_page.
+ */
+ post_alloc_hook(page, order, __GFP_MOVABLE);
+ __free_pages(page, order);
+ if (pfn > high_pfn)
+ high_pfn = pfn;
+ }
+ freepages[order].nr_pages = 0;
+ }
+ return high_pfn;
}
#ifdef CONFIG_COMPACTION
@@ -583,7 +605,7 @@ static bool compact_unlock_should_abort(spinlock_t *lock,
static unsigned long isolate_freepages_block(struct compact_control *cc,
unsigned long *start_pfn,
unsigned long end_pfn,
- struct list_head *freelist,
+ struct page_list *freelist,
unsigned int stride,
bool strict)
{
@@ -657,7 +679,8 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
nr_scanned += isolated - 1;
total_isolated += isolated;
cc->nr_freepages += isolated;
- list_add_tail(&page->lru, freelist);
+ list_add_tail(&page->lru, &freelist[order].pages);
+ freelist[order].nr_pages++;
if (!strict && cc->nr_migratepages <= cc->nr_freepages) {
blockpfn += isolated;
@@ -722,7 +745,11 @@ isolate_freepages_range(struct compact_control *cc,
unsigned long start_pfn, unsigned long end_pfn)
{
unsigned long isolated, pfn, block_start_pfn, block_end_pfn;
- LIST_HEAD(freelist);
+ int order;
+ struct page_list tmp_freepages[NR_PAGE_ORDERS];
+
+ for (order = 0; order < NR_PAGE_ORDERS; order++)
+ init_page_list(&tmp_freepages[order]);
pfn = start_pfn;
block_start_pfn = pageblock_start_pfn(pfn);
@@ -753,7 +780,7 @@ isolate_freepages_range(struct compact_control *cc,
break;
isolated = isolate_freepages_block(cc, &isolate_start_pfn,
- block_end_pfn, &freelist, 0, true);
+ block_end_pfn, tmp_freepages, 0, true);
/*
* In strict mode, isolate_freepages_block() returns 0 if
@@ -770,15 +797,15 @@ isolate_freepages_range(struct compact_control *cc,
*/
}
- /* __isolate_free_page() does not map the pages */
- split_map_pages(&freelist);
-
if (pfn < end_pfn) {
/* Loop terminated early, cleanup. */
- release_freepages(&freelist);
+ release_free_list(tmp_freepages);
return 0;
}
+ /* __isolate_free_page() does not map the pages */
+ split_map_pages(tmp_freepages);
+
/* We don't use freelists for anything. */
return pfn;
}
@@ -1462,7 +1489,7 @@ fast_isolate_around(struct compact_control *cc, unsigned long pfn)
if (!page)
return;
- isolate_freepages_block(cc, &start_pfn, end_pfn, &cc->freepages, 1, false);
+ isolate_freepages_block(cc, &start_pfn, end_pfn, cc->freepages, 1, false);
/* Skip this pageblock in the future as it's full or nearly full */
if (start_pfn == end_pfn && !cc->no_set_skip_hint)
@@ -1591,7 +1618,7 @@ static void fast_isolate_freepages(struct compact_control *cc)
nr_scanned += nr_isolated - 1;
total_isolated += nr_isolated;
cc->nr_freepages += nr_isolated;
- list_add_tail(&page->lru, &cc->freepages);
+ list_add_tail(&page->lru, &cc->freepages[order].pages);
count_compact_events(COMPACTISOLATED, nr_isolated);
} else {
/* If isolation fails, abort the search */
@@ -1668,13 +1695,12 @@ static void isolate_freepages(struct compact_control *cc)
unsigned long isolate_start_pfn; /* exact pfn we start at */
unsigned long block_end_pfn; /* end of current pageblock */
unsigned long low_pfn; /* lowest pfn scanner is able to scan */
- struct list_head *freelist = &cc->freepages;
unsigned int stride;
/* Try a small search of the free lists for a candidate */
fast_isolate_freepages(cc);
if (cc->nr_freepages)
- goto splitmap;
+ return;
/*
* Initialise the free scanner. The starting point is where we last
@@ -1734,7 +1760,7 @@ static void isolate_freepages(struct compact_control *cc)
/* Found a block suitable for isolating free pages from. */
nr_isolated = isolate_freepages_block(cc, &isolate_start_pfn,
- block_end_pfn, freelist, stride, false);
+ block_end_pfn, cc->freepages, stride, false);
/* Update the skip hint if the full pageblock was scanned */
if (isolate_start_pfn == block_end_pfn)
@@ -1775,10 +1801,6 @@ static void isolate_freepages(struct compact_control *cc)
* and the loop terminated due to isolate_start_pfn < low_pfn
*/
cc->free_pfn = isolate_start_pfn;
-
-splitmap:
- /* __isolate_free_page() does not map the pages */
- split_map_pages(freelist);
}
/*
@@ -1789,23 +1811,22 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data)
{
struct compact_control *cc = (struct compact_control *)data;
struct folio *dst;
+ int order = folio_order(src);
- /* this makes migrate_pages() split the source page and retry */
- if (folio_test_large(src) > 0)
- return NULL;
-
- if (list_empty(&cc->freepages)) {
+ if (!cc->freepages[order].nr_pages) {
isolate_freepages(cc);
-
- if (list_empty(&cc->freepages))
+ if (!cc->freepages[order].nr_pages)
return NULL;
}
- dst = list_entry(cc->freepages.next, struct folio, lru);
+ dst = list_first_entry(&cc->freepages[order].pages, struct folio, lru);
+ cc->freepages[order].nr_pages--;
list_del(&dst->lru);
- cc->nr_freepages--;
-
- return dst;
+ post_alloc_hook(&dst->page, order, __GFP_MOVABLE);
+ if (order)
+ prep_compound_page(&dst->page, order);
+ cc->nr_freepages -= 1 << order;
+ return page_rmappable_folio(&dst->page);
}
/*
@@ -1816,9 +1837,17 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data)
static void compaction_free(struct folio *dst, unsigned long data)
{
struct compact_control *cc = (struct compact_control *)data;
+ int order = folio_order(dst);
+ struct page *page = &dst->page;
+
+ folio_set_count(dst, 0);
+ free_pages_prepare_fpi_none(page, order);
- list_add(&dst->lru, &cc->freepages);
- cc->nr_freepages++;
+ INIT_LIST_HEAD(&dst->lru);
+
+ list_add(&dst->lru, &cc->freepages[order].pages);
+ cc->freepages[order].nr_pages++;
+ cc->nr_freepages += 1 << order;
}
/* possible outcome of isolate_migratepages */
@@ -2442,6 +2471,7 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
const bool sync = cc->mode != MIGRATE_ASYNC;
bool update_cached;
unsigned int nr_succeeded = 0;
+ int order;
/*
* These counters track activities during zone compaction. Initialize
@@ -2451,7 +2481,8 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
cc->total_free_scanned = 0;
cc->nr_migratepages = 0;
cc->nr_freepages = 0;
- INIT_LIST_HEAD(&cc->freepages);
+ for (order = 0; order < NR_PAGE_ORDERS; order++)
+ init_page_list(&cc->freepages[order]);
INIT_LIST_HEAD(&cc->migratepages);
cc->migratetype = gfp_migratetype(cc->gfp_mask);
@@ -2637,7 +2668,7 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
* so we don't leave any returned pages behind in the next attempt.
*/
if (cc->nr_freepages > 0) {
- unsigned long free_pfn = release_freepages(&cc->freepages);
+ unsigned long free_pfn = release_free_list(cc->freepages);
cc->nr_freepages = 0;
VM_BUG_ON(free_pfn == 0);
@@ -2656,7 +2687,6 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
trace_mm_compaction_end(cc, start_pfn, end_pfn, sync, ret);
- VM_BUG_ON(!list_empty(&cc->freepages));
VM_BUG_ON(!list_empty(&cc->migratepages));
return ret;
diff --git a/mm/internal.h b/mm/internal.h
index f309a010d50f..886040a907d3 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -447,6 +447,8 @@ extern void prep_compound_page(struct page *page, unsigned int order);
extern void post_alloc_hook(struct page *page, unsigned int order,
gfp_t gfp_flags);
+extern bool free_pages_prepare_fpi_none(struct page *page, unsigned int order);
+
extern int user_min_free_kbytes;
extern void free_unref_page(struct page *page, unsigned int order);
@@ -473,6 +475,11 @@ int split_free_page(struct page *free_page,
/*
* in mm/compaction.c
*/
+
+struct page_list {
+ struct list_head pages;
+ unsigned long nr_pages;
+};
/*
* compact_control is used to track pages being migrated and the free pages
* they are being migrated to during memory compaction. The free_pfn starts
@@ -481,7 +488,7 @@ int split_free_page(struct page *free_page,
* completes when free_pfn <= migrate_pfn
*/
struct compact_control {
- struct list_head freepages; /* List of free pages to migrate to */
+ struct page_list freepages[NR_PAGE_ORDERS]; /* List of free pages to migrate to */
struct list_head migratepages; /* List of pages being migrated */
unsigned int nr_freepages; /* Number of isolated free pages */
unsigned int nr_migratepages; /* Number of pages to migrate */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5be4cd8f6b5a..c7c135e6d5ee 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1179,6 +1179,12 @@ static __always_inline bool free_pages_prepare(struct page *page,
return true;
}
+__always_inline bool free_pages_prepare_fpi_none(struct page *page,
+ unsigned int order)
+{
+ return free_pages_prepare(page, order, FPI_NONE);
+}
+
/*
* Frees a number of pages from the PCP lists
* Assumes all pages on list are in same zone.
--
2.43.0
On 1/23/2024 11:46 AM, Zi Yan wrote:
> From: Zi Yan <[email protected]>
>
> migrate_pages() supports >0 order folio migration and during compaction,
> even if compaction_alloc() cannot provide >0 order free pages,
> migrate_pages() can split the source page and try to migrate the base pages
> from the split. It can be a baseline and start point for adding support for
> compacting >0 order folios.
>
> Suggested-by: Huang Ying <[email protected]>
> Signed-off-by: Zi Yan <[email protected]>
LGTM.
Reviewed-by: Baolin Wang <[email protected]>
> ---
> mm/compaction.c | 43 +++++++++++++++++++++++++++++++++++--------
> 1 file changed, 35 insertions(+), 8 deletions(-)
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 27ada42924d5..61389540e1f1 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -816,6 +816,21 @@ static bool too_many_isolated(struct compact_control *cc)
> return too_many;
> }
>
> +/*
> + * 1. if the page order is larger than or equal to target_order (i.e.,
> + * cc->order and when it is not -1 for global compaction), skip it since
> + * target_order already indicates no free page with larger than target_order
> + * exists and later migrating it will most likely fail;
> + *
> + * 2. compacting > pageblock_order pages does not improve memory fragmentation,
> + * skip them;
> + */
> +static bool skip_isolation_on_order(int order, int target_order)
> +{
> + return (target_order != -1 && order >= target_order) ||
> + order >= pageblock_order;
> +}
> +
> /**
> * isolate_migratepages_block() - isolate all migrate-able pages within
> * a single pageblock
> @@ -1009,7 +1024,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
> /*
> * Regardless of being on LRU, compound pages such as THP and
> * hugetlbfs are not to be compacted unless we are attempting
> - * an allocation much larger than the huge page size (eg CMA).
> + * an allocation larger than the compound page size.
> * We can potentially save a lot of iterations if we skip them
> * at once. The check is racy, but we can consider only valid
> * values and the only danger is skipping too much.
> @@ -1017,11 +1032,18 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
> if (PageCompound(page) && !cc->alloc_contig) {
> const unsigned int order = compound_order(page);
>
> - if (likely(order <= MAX_PAGE_ORDER)) {
> - low_pfn += (1UL << order) - 1;
> - nr_scanned += (1UL << order) - 1;
> + /*
> + * Skip based on page order and compaction target order
> + * and skip hugetlbfs pages.
> + */
> + if (skip_isolation_on_order(order, cc->order) ||
> + PageHuge(page)) {
> + if (order <= MAX_PAGE_ORDER) {
> + low_pfn += (1UL << order) - 1;
> + nr_scanned += (1UL << order) - 1;
> + }
> + goto isolate_fail;
> }
> - goto isolate_fail;
> }
>
> /*
> @@ -1146,10 +1168,11 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
> }
>
> /*
> - * folio become large since the non-locked check,
> - * and it's on LRU.
> + * Check LRU folio order under the lock
> */
> - if (unlikely(folio_test_large(folio) && !cc->alloc_contig)) {
> + if (unlikely(skip_isolation_on_order(folio_order(folio),
> + cc->order) &&
> + !cc->alloc_contig)) {
> low_pfn += folio_nr_pages(folio) - 1;
> nr_scanned += folio_nr_pages(folio) - 1;
> folio_set_lru(folio);
> @@ -1767,6 +1790,10 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data)
> struct compact_control *cc = (struct compact_control *)data;
> struct folio *dst;
>
> + /* this makes migrate_pages() split the source page and retry */
> + if (folio_test_large(src) > 0)
> + return NULL;
> +
> if (list_empty(&cc->freepages)) {
> isolate_freepages(cc);
>
On 1/23/2024 11:46 AM, Zi Yan wrote:
> From: Zi Yan <[email protected]>
>
> Hi all,
>
> This patchset enables >0 order folio memory compaction, which is one of
> the prerequisitions for large folio support[1]. It is on top of
> mm-everything-2024-01-18-22-21.
>
> I am aware of that split free pages is necessary for folio
> migration in compaction, since if >0 order free pages are never split
> and no order-0 free page is scanned, compaction will end prematurely due
> to migration returns -ENOMEM. Free page split becomes a must instead of
> an optimization.
>
> Some applications from vm-scalability show different performance trends
> on default LRU and CONFIG_LRU_GEN from patch 1 (split folio during compaction),
> to patch 2 (folio migration during compaction), to patch 3 (folio
> migration during compaction with free page split). I am looking into it.
>
> lkp ncompare results (with >5% delta) for default LRU and CONFIG_LRU_GEN are
> shown at the bottom (on a 8-CPU (Intel Xeon E5-2650 v4 @ 2.20GHz) 16G VM).
Overall, I haven't found any obvious issues, thanks for your work.
However I got some percentage regression when running thpcompact on my
machine(16 cores and 120G memory) without enabling mTHP:
k6.8-rc1 k6.8-rc1-patched
Percentage huge-1 86.19 ( 0.00%) 51.17 ( -40.63%)
Percentage huge-3 93.64 ( 0.00%) 42.48 ( -54.64%)
Percentage huge-5 94.93 ( 0.00%) 31.06 ( -67.28%)
Percentage huge-7 95.40 ( 0.00%) 19.09 ( -79.99%)
Percentage huge-12 93.51 ( 0.00%) 32.06 ( -65.71%)
Percentage huge-18 83.02 ( 0.00%) 54.58 ( -34.26%)
Percentage huge-24 83.17 ( 0.00%) 49.61 ( -40.35%)
Percentage huge-30 96.69 ( 0.00%) 59.82 ( -38.13%)
Percentage huge-32 95.52 ( 0.00%) 59.20 ( -38.03%)
Ops Compaction stalls 229710.00 554846.00
Ops Compaction success 144177.00 9351.00
Ops Compaction failures 85533.00 545495.00
Ops Compaction efficiency 62.76 1.69
Ops Page migrate success 60333689.00 11687573.00
Ops Page migrate failure 25818.00 459621.00
Ops Compaction pages isolated 127723211.00 224420997.00
Ops Compaction migrate scanned 142498744.00 173345194.00
Ops Compaction free scanned 1159752360.00 624633726.00
Ops Compact scan efficiency 12.29 27.75
Ops Compaction cost 66050.96 17615.55
I did not have time to analyze this issue, just providing you some test
information. And I will measure the compaction efficiency of mTHP if I
find some time.
> From V1 [2]:
> 1. Used folio_test_large() instead of folio_order() > 0. (per Matthew
> Wilcox)
>
> 2. Fixed code rebase error. (per Baolin Wang)
>
> 3. Used list_split_init() instead of list_split(). (per Ryan Boberts)
>
> 4. Added free_pages_prepare_fpi_none() to avoid duplicate free page code
> in compaction_free().
>
> 5. Dropped source page order sorting patch.
>
> From RFC [1]:
> 1. Enabled >0 order folio compaction in the first patch by splitting all
> to-be-migrated folios. (per Huang, Ying)
>
> 2. Stopped isolating compound pages with order greater than cc->order
> to avoid wasting effort, since cc->order gives a hint that no free pages
> with order greater than it exist, thus migrating the compound pages will fail.
> (per Baolin Wang)
>
> 3. Retained the folio check within lru lock. (per Baolin Wang)
>
> 4. Made isolate_freepages_block() generate order-sorted multi lists.
> (per Johannes Weiner)
>
> Overview
> ===
>
> To support >0 order folio compaction, the patchset changes how free pages used
> for migration are kept during compaction. Free pages used to be split into
> order-0 pages that are post allocation processed (i.e., PageBuddy flag cleared,
> page order stored in page->private is zeroed, and page reference is set to 1).
> Now all free pages are kept in a MAX_ORDER+1 array of page lists based
> on their order without post allocation process. When migrate_pages() asks for
> a new page, one of the free pages, based on the requested page order, is
> then processed and given out.
>
>
> Feel free to give comments and ask questions.
>
> Thanks.
>
> [1] https://lore.kernel.org/linux-mm/[email protected]/
> [2] https://lore.kernel.org/linux-mm/[email protected]/
>
> vm-scalability results on CONFIG_LRU_GEN
> ===
>
> =========================================================================================
> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
> gcc-13/defconfig/debian/300s/qemu-vm/small-allocs/vm-scalability
>
> commit:
> 6.7.0-rc4+
> 6.7.0-rc4-split-folio-in-compaction+
> 6.7.0-rc4-folio-migration-in-compaction+
> 6.7.0-rc4-folio-migration-free-page-split+
>
> 6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
> ---------------- --------------------------- --------------------------- ---------------------------
> %stddev %change %stddev %change %stddev %change %stddev
> \ | \ | \ | \
> 2024326 +35.5% 2743772 ± 41% +364.0% 9392198 ± 35% +31.0% 2651634 vm-scalability.throughput
>
> =========================================================================================
> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
> gcc-13/defconfig/debian/300s/qemu-vm/small-allocs-mt/vm-scalability
>
> commit:
> 6.7.0-rc4+
> 6.7.0-rc4-split-folio-in-compaction+
> 6.7.0-rc4-folio-migration-in-compaction+
> 6.7.0-rc4-folio-migration-free-page-split+
>
> 6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
> ---------------- --------------------------- --------------------------- ---------------------------
> %stddev %change %stddev %change %stddev %change %stddev
> \ | \ | \ | \
> 1450189 +0.9% 1463418 +30.4% 1891610 ± 22% +0.3% 1454100 vm-scalability.throughput
>
> =========================================================================================
> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
> gcc-13/defconfig/debian/300s/qemu-vm/mmap-xread-seq-mt/vm-scalability
>
> commit:
> 6.7.0-rc4+
> 6.7.0-rc4-split-folio-in-compaction+
> 6.7.0-rc4-folio-migration-in-compaction+
> 6.7.0-rc4-folio-migration-free-page-split+
>
> 6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
> ---------------- --------------------------- --------------------------- ---------------------------
> %stddev %change %stddev %change %stddev %change %stddev
> \ | \ | \ | \
> 14428848 ± 27% -51.7% 6963308 ± 73% +13.5% 16372621 +11.2% 16046511 vm-scalability.throughput
>
> =========================================================================================
> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
> gcc-13/defconfig/debian/300s/qemu-vm/mmap-pread-seq/vm-scalability
>
> commit:
> 6.7.0-rc4+
> 6.7.0-rc4-split-folio-in-compaction+
> 6.7.0-rc4-folio-migration-in-compaction+
> 6.7.0-rc4-folio-migration-free-page-split+
>
> 6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
> ---------------- --------------------------- --------------------------- ---------------------------
> %stddev %change %stddev %change %stddev %change %stddev
> \ | \ | \ | \
> 13569502 ± 24% -45.9% 7340064 ± 59% +12.3% 15240531 +10.4% 14983705 vm-scalability.throughput
>
> =========================================================================================
> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
> gcc-13/defconfig/debian/300s/qemu-vm/mmap-pread-seq-mt/vm-scalability
>
> commit:
> 6.7.0-rc4+
> 6.7.0-rc4-split-folio-in-compaction+
> 6.7.0-rc4-folio-migration-in-compaction+
> 6.7.0-rc4-folio-migration-free-page-split+
>
> 6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
> ---------------- --------------------------- --------------------------- ---------------------------
> %stddev %change %stddev %change %stddev %change %stddev
> \ | \ | \ | \
> 13305823 ± 24% -45.1% 7299664 ± 56% +12.5% 14974725 +10.4% 14695963 vm-scalability.throughput
>
> =========================================================================================
> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
> gcc-13/defconfig/debian/300s/qemu-vm/lru-file-readtwice/vm-scalability
>
> commit:
> 6.7.0-rc4+
> 6.7.0-rc4-split-folio-in-compaction+
> 6.7.0-rc4-folio-migration-in-compaction+
> 6.7.0-rc4-folio-migration-free-page-split+
>
> 6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
> ---------------- --------------------------- --------------------------- ---------------------------
> %stddev %change %stddev %change %stddev %change %stddev
> \ | \ | \ | \
> 13244376 ± 28% +54.2% 20425838 ± 23% -4.4% 12660113 ± 3% -9.0% 12045809 ± 3% vm-scalability.throughput
>
> =========================================================================================
> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
> gcc-13/defconfig/debian/300s/qemu-vm/lru-file-mmap-read/vm-scalability
>
> commit:
> 6.7.0-rc4+
> 6.7.0-rc4-split-folio-in-compaction+
> 6.7.0-rc4-folio-migration-in-compaction+
> 6.7.0-rc4-folio-migration-free-page-split+
>
> 6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
> ---------------- --------------------------- --------------------------- ---------------------------
> %stddev %change %stddev %change %stddev %change %stddev
> \ | \ | \ | \
> 7021425 ± 11% -20.9% 5556751 ± 19% +14.8% 8057811 ± 3% +9.4% 7678613 ± 4% vm-scalability.throughput
>
> =========================================================================================
> compiler/kconfig/rootfs/runtime/size/tbox_group/test/testcase:
> gcc-13/defconfig/debian/300s/256G/qemu-vm/msync/vm-scalability
>
> commit:
> 6.7.0-rc4+
> 6.7.0-rc4-split-folio-in-compaction+
> 6.7.0-rc4-folio-migration-in-compaction+
> 6.7.0-rc4-folio-migration-free-page-split+
>
> 6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
> ---------------- --------------------------- --------------------------- ---------------------------
> %stddev %change %stddev %change %stddev %change %stddev
> \ | \ | \ | \
> 1208994 ±137% +263.5% 4394683 ± 49% -49.4% 611204 ± 6% -48.1% 627937 ± 13% vm-scalability.throughput
>
>
>
> vm-scalability results on default LRU (with -no-mglru suffix)
> ===
>
> =========================================================================================
> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
> gcc-13/defconfig/debian/300s/qemu-vm/lru-file-readtwice/vm-scalability
>
> commit:
> 6.7.0-rc4-no-mglru+
> 6.7.0-rc4-split-folio-in-compaction-no-mglru+
> 6.7.0-rc4-folio-migration-in-compaction-no-mglru+
> 6.7.0-rc4-folio-migration-free-page-split-no-mglru+
>
> 6.7.0-rc4-no-mgl 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
> ---------------- --------------------------- --------------------------- ---------------------------
> %stddev %change %stddev %change %stddev %change %stddev
> \ | \ | \ | \
> 8412072 ± 3% +32.1% 11114537 ± 41% +3.5% 8703491 ± 3% +1.5% 8536343 ± 3% vm-scalability.throughput
>
> =========================================================================================
> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
> gcc-13/defconfig/debian/300s/qemu-vm/lru-file-mmap-read/vm-scalability
>
> commit:
> 6.7.0-rc4-no-mglru+
> 6.7.0-rc4-split-folio-in-compaction-no-mglru+
> 6.7.0-rc4-folio-migration-in-compaction-no-mglru+
> 6.7.0-rc4-folio-migration-free-page-split-no-mglru+
>
> 6.7.0-rc4-no-mgl 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
> ---------------- --------------------------- --------------------------- ---------------------------
> %stddev %change %stddev %change %stddev %change %stddev
> \ | \ | \ | \
> 7095358 +10.8% 7863635 ± 16% +5.5% 7484110 +1.5% 7200666 ± 4% vm-scalability.throughput
>
>
> Zi Yan (3):
> mm/compaction: enable compacting >0 order folios.
> mm/compaction: add support for >0 order folio memory compaction.
> mm/compaction: optimize >0 order folio compaction with free page
> split.
>
> mm/compaction.c | 218 ++++++++++++++++++++++++++++++++++--------------
> mm/internal.h | 9 +-
> mm/page_alloc.c | 6 ++
> 3 files changed, 169 insertions(+), 64 deletions(-)
>
On 26 Jan 2024, at 4:03, Baolin Wang wrote:
> On 1/23/2024 11:46 AM, Zi Yan wrote:
>> From: Zi Yan <[email protected]>
>>
>> Hi all,
>>
>> This patchset enables >0 order folio memory compaction, which is one of
>> the prerequisitions for large folio support[1]. It is on top of
>> mm-everything-2024-01-18-22-21.
>>
>> I am aware of that split free pages is necessary for folio
>> migration in compaction, since if >0 order free pages are never split
>> and no order-0 free page is scanned, compaction will end prematurely due
>> to migration returns -ENOMEM. Free page split becomes a must instead of
>> an optimization.
>>
>> Some applications from vm-scalability show different performance trends
>> on default LRU and CONFIG_LRU_GEN from patch 1 (split folio during compaction),
>> to patch 2 (folio migration during compaction), to patch 3 (folio
>> migration during compaction with free page split). I am looking into it.
>>
>> lkp ncompare results (with >5% delta) for default LRU and CONFIG_LRU_GEN are
>> shown at the bottom (on a 8-CPU (Intel Xeon E5-2650 v4 @ 2.20GHz) 16G VM).
>
> Overall, I haven't found any obvious issues, thanks for your work. However I got some percentage regression when running thpcompact on my machine(16 cores and 120G memory) without enabling mTHP:
> k6.8-rc1 k6.8-rc1-patched
> Percentage huge-1 86.19 ( 0.00%) 51.17 ( -40.63%)
> Percentage huge-3 93.64 ( 0.00%) 42.48 ( -54.64%)
> Percentage huge-5 94.93 ( 0.00%) 31.06 ( -67.28%)
> Percentage huge-7 95.40 ( 0.00%) 19.09 ( -79.99%)
> Percentage huge-12 93.51 ( 0.00%) 32.06 ( -65.71%)
> Percentage huge-18 83.02 ( 0.00%) 54.58 ( -34.26%)
> Percentage huge-24 83.17 ( 0.00%) 49.61 ( -40.35%)
> Percentage huge-30 96.69 ( 0.00%) 59.82 ( -38.13%)
> Percentage huge-32 95.52 ( 0.00%) 59.20 ( -38.03%)
>
> Ops Compaction stalls 229710.00 554846.00
> Ops Compaction success 144177.00 9351.00
> Ops Compaction failures 85533.00 545495.00
> Ops Compaction efficiency 62.76 1.69
> Ops Page migrate success 60333689.00 11687573.00
> Ops Page migrate failure 25818.00 459621.00
> Ops Compaction pages isolated 127723211.00 224420997.00
> Ops Compaction migrate scanned 142498744.00 173345194.00
> Ops Compaction free scanned 1159752360.00 624633726.00
> Ops Compact scan efficiency 12.29 27.75
> Ops Compaction cost 66050.96 17615.55
>
> I did not have time to analyze this issue, just providing you some test information. And I will measure the compaction efficiency of mTHP if I find some time.
Thanks a lot. These are useful numbers. I can see that the number of
migration failures doubled and only ~1/5 of successes. I will use
thpcompact to look into the issues.
>
>> From V1 [2]:
>> 1. Used folio_test_large() instead of folio_order() > 0. (per Matthew
>> Wilcox)
>>
>> 2. Fixed code rebase error. (per Baolin Wang)
>>
>> 3. Used list_split_init() instead of list_split(). (per Ryan Boberts)
>>
>> 4. Added free_pages_prepare_fpi_none() to avoid duplicate free page code
>> in compaction_free().
>>
>> 5. Dropped source page order sorting patch.
>>
>> From RFC [1]:
>> 1. Enabled >0 order folio compaction in the first patch by splitting all
>> to-be-migrated folios. (per Huang, Ying)
>>
>> 2. Stopped isolating compound pages with order greater than cc->order
>> to avoid wasting effort, since cc->order gives a hint that no free pages
>> with order greater than it exist, thus migrating the compound pages will fail.
>> (per Baolin Wang)
>>
>> 3. Retained the folio check within lru lock. (per Baolin Wang)
>>
>> 4. Made isolate_freepages_block() generate order-sorted multi lists.
>> (per Johannes Weiner)
>>
>> Overview
>> ===
>>
>> To support >0 order folio compaction, the patchset changes how free pages used
>> for migration are kept during compaction. Free pages used to be split into
>> order-0 pages that are post allocation processed (i.e., PageBuddy flag cleared,
>> page order stored in page->private is zeroed, and page reference is set to 1).
>> Now all free pages are kept in a MAX_ORDER+1 array of page lists based
>> on their order without post allocation process. When migrate_pages() asks for
>> a new page, one of the free pages, based on the requested page order, is
>> then processed and given out.
>>
>>
>> Feel free to give comments and ask questions.
>>
>> Thanks.
>>
>> [1] https://lore.kernel.org/linux-mm/[email protected]/
>> [2] https://lore.kernel.org/linux-mm/[email protected]/
>>
>> vm-scalability results on CONFIG_LRU_GEN
>> ===
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>> gcc-13/defconfig/debian/300s/qemu-vm/small-allocs/vm-scalability
>>
>> commit:
>> 6.7.0-rc4+
>> 6.7.0-rc4-split-folio-in-compaction+
>> 6.7.0-rc4-folio-migration-in-compaction+
>> 6.7.0-rc4-folio-migration-free-page-split+
>>
>> 6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>> %stddev %change %stddev %change %stddev %change %stddev
>> \ | \ | \ | \
>> 2024326 +35.5% 2743772 ± 41% +364.0% 9392198 ± 35% +31.0% 2651634 vm-scalability.throughput
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>> gcc-13/defconfig/debian/300s/qemu-vm/small-allocs-mt/vm-scalability
>>
>> commit:
>> 6.7.0-rc4+
>> 6.7.0-rc4-split-folio-in-compaction+
>> 6.7.0-rc4-folio-migration-in-compaction+
>> 6.7.0-rc4-folio-migration-free-page-split+
>>
>> 6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>> %stddev %change %stddev %change %stddev %change %stddev
>> \ | \ | \ | \
>> 1450189 +0.9% 1463418 +30.4% 1891610 ± 22% +0.3% 1454100 vm-scalability.throughput
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>> gcc-13/defconfig/debian/300s/qemu-vm/mmap-xread-seq-mt/vm-scalability
>>
>> commit:
>> 6.7.0-rc4+
>> 6.7.0-rc4-split-folio-in-compaction+
>> 6.7.0-rc4-folio-migration-in-compaction+
>> 6.7.0-rc4-folio-migration-free-page-split+
>>
>> 6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>> %stddev %change %stddev %change %stddev %change %stddev
>> \ | \ | \ | \
>> 14428848 ± 27% -51.7% 6963308 ± 73% +13.5% 16372621 +11.2% 16046511 vm-scalability.throughput
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>> gcc-13/defconfig/debian/300s/qemu-vm/mmap-pread-seq/vm-scalability
>>
>> commit:
>> 6.7.0-rc4+
>> 6.7.0-rc4-split-folio-in-compaction+
>> 6.7.0-rc4-folio-migration-in-compaction+
>> 6.7.0-rc4-folio-migration-free-page-split+
>>
>> 6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>> %stddev %change %stddev %change %stddev %change %stddev
>> \ | \ | \ | \
>> 13569502 ± 24% -45.9% 7340064 ± 59% +12.3% 15240531 +10.4% 14983705 vm-scalability.throughput
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>> gcc-13/defconfig/debian/300s/qemu-vm/mmap-pread-seq-mt/vm-scalability
>>
>> commit:
>> 6.7.0-rc4+
>> 6.7.0-rc4-split-folio-in-compaction+
>> 6.7.0-rc4-folio-migration-in-compaction+
>> 6.7.0-rc4-folio-migration-free-page-split+
>>
>> 6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>> %stddev %change %stddev %change %stddev %change %stddev
>> \ | \ | \ | \
>> 13305823 ± 24% -45.1% 7299664 ± 56% +12.5% 14974725 +10.4% 14695963 vm-scalability.throughput
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>> gcc-13/defconfig/debian/300s/qemu-vm/lru-file-readtwice/vm-scalability
>>
>> commit:
>> 6.7.0-rc4+
>> 6.7.0-rc4-split-folio-in-compaction+
>> 6.7.0-rc4-folio-migration-in-compaction+
>> 6.7.0-rc4-folio-migration-free-page-split+
>>
>> 6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>> %stddev %change %stddev %change %stddev %change %stddev
>> \ | \ | \ | \
>> 13244376 ± 28% +54.2% 20425838 ± 23% -4.4% 12660113 ± 3% -9.0% 12045809 ± 3% vm-scalability.throughput
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>> gcc-13/defconfig/debian/300s/qemu-vm/lru-file-mmap-read/vm-scalability
>>
>> commit:
>> 6.7.0-rc4+
>> 6.7.0-rc4-split-folio-in-compaction+
>> 6.7.0-rc4-folio-migration-in-compaction+
>> 6.7.0-rc4-folio-migration-free-page-split+
>>
>> 6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>> %stddev %change %stddev %change %stddev %change %stddev
>> \ | \ | \ | \
>> 7021425 ± 11% -20.9% 5556751 ± 19% +14.8% 8057811 ± 3% +9.4% 7678613 ± 4% vm-scalability.throughput
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/size/tbox_group/test/testcase:
>> gcc-13/defconfig/debian/300s/256G/qemu-vm/msync/vm-scalability
>>
>> commit:
>> 6.7.0-rc4+
>> 6.7.0-rc4-split-folio-in-compaction+
>> 6.7.0-rc4-folio-migration-in-compaction+
>> 6.7.0-rc4-folio-migration-free-page-split+
>>
>> 6.7.0-rc4+ 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>> %stddev %change %stddev %change %stddev %change %stddev
>> \ | \ | \ | \
>> 1208994 ±137% +263.5% 4394683 ± 49% -49.4% 611204 ± 6% -48.1% 627937 ± 13% vm-scalability.throughput
>>
>>
>>
>> vm-scalability results on default LRU (with -no-mglru suffix)
>> ===
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>> gcc-13/defconfig/debian/300s/qemu-vm/lru-file-readtwice/vm-scalability
>>
>> commit:
>> 6.7.0-rc4-no-mglru+
>> 6.7.0-rc4-split-folio-in-compaction-no-mglru+
>> 6.7.0-rc4-folio-migration-in-compaction-no-mglru+
>> 6.7.0-rc4-folio-migration-free-page-split-no-mglru+
>>
>> 6.7.0-rc4-no-mgl 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>> %stddev %change %stddev %change %stddev %change %stddev
>> \ | \ | \ | \
>> 8412072 ± 3% +32.1% 11114537 ± 41% +3.5% 8703491 ± 3% +1.5% 8536343 ± 3% vm-scalability.throughput
>>
>> =========================================================================================
>> compiler/kconfig/rootfs/runtime/tbox_group/test/testcase:
>> gcc-13/defconfig/debian/300s/qemu-vm/lru-file-mmap-read/vm-scalability
>>
>> commit:
>> 6.7.0-rc4-no-mglru+
>> 6.7.0-rc4-split-folio-in-compaction-no-mglru+
>> 6.7.0-rc4-folio-migration-in-compaction-no-mglru+
>> 6.7.0-rc4-folio-migration-free-page-split-no-mglru+
>>
>> 6.7.0-rc4-no-mgl 6.7.0-rc4-split-folio-in-co 6.7.0-rc4-folio-migration-i 6.7.0-rc4-folio-migration-f
>> ---------------- --------------------------- --------------------------- ---------------------------
>> %stddev %change %stddev %change %stddev %change %stddev
>> \ | \ | \ | \
>> 7095358 +10.8% 7863635 ± 16% +5.5% 7484110 +1.5% 7200666 ± 4% vm-scalability.throughput
>>
>>
>> Zi Yan (3):
>> mm/compaction: enable compacting >0 order folios.
>> mm/compaction: add support for >0 order folio memory compaction.
>> mm/compaction: optimize >0 order folio compaction with free page
>> split.
>>
>> mm/compaction.c | 218 ++++++++++++++++++++++++++++++++++--------------
>> mm/internal.h | 9 +-
>> mm/page_alloc.c | 6 ++
>> 3 files changed, 169 insertions(+), 64 deletions(-)
>>
--
Best Regards,
Yan, Zi
On 22 Jan 2024, at 22:46, Zi Yan wrote:
> From: Zi Yan <[email protected]>
>
> Before last commit, memory compaction only migrates order-0 folios and
> skips >0 order folios. Last commit splits all >0 order folios during
> compaction. This commit migrates >0 order folios during compaction by
> keeping isolated free pages at their original size without splitting them
> into order-0 pages and using them directly during migration process.
>
> What is different from the prior implementation:
> 1. All isolated free pages are kept in a NR_PAGE_ORDERS array of page
> lists, where each page list stores free pages in the same order.
> 2. All free pages are not post_alloc_hook() processed nor buddy pages,
> although their orders are stored in first page's private like buddy
> pages.
> 3. During migration, in new page allocation time (i.e., in
> compaction_alloc()), free pages are then processed by post_alloc_hook().
> When migration fails and a new page is returned (i.e., in
> compaction_free()), free pages are restored by reversing the
> post_alloc_hook() operations using newly added
> free_pages_prepare_fpi_none().
>
> Step 3 is done for a latter optimization that splitting and/or merging free
> pages during compaction becomes easier.
>
> Note: without splitting free pages, compaction can end prematurely due to
> migration will return -ENOMEM even if there is free pages. This happens
> when no order-0 free page exist and compaction_alloc() return NULL.
>
> Signed-off-by: Zi Yan <[email protected]>
> ---
> mm/compaction.c | 148 +++++++++++++++++++++++++++++-------------------
> mm/internal.h | 9 ++-
> mm/page_alloc.c | 6 ++
> 3 files changed, 103 insertions(+), 60 deletions(-)
>
<snip>
> @@ -1462,7 +1489,7 @@ fast_isolate_around(struct compact_control *cc, unsigned long pfn)
> if (!page)
> return;
>
> - isolate_freepages_block(cc, &start_pfn, end_pfn, &cc->freepages, 1, false);
> + isolate_freepages_block(cc, &start_pfn, end_pfn, cc->freepages, 1, false);
>
> /* Skip this pageblock in the future as it's full or nearly full */
> if (start_pfn == end_pfn && !cc->no_set_skip_hint)
> @@ -1591,7 +1618,7 @@ static void fast_isolate_freepages(struct compact_control *cc)
> nr_scanned += nr_isolated - 1;
> total_isolated += nr_isolated;
> cc->nr_freepages += nr_isolated;
> - list_add_tail(&page->lru, &cc->freepages);
> + list_add_tail(&page->lru, &cc->freepages[order].pages);
I did not increase nr_pages here, so compaction_alloc() thought no free page
was isolated.
This is the fix:
diff --git a/mm/compaction.c b/mm/compaction.c
index 335a6f6787e4..fa9993c8a389 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1638,6 +1638,7 @@ static void fast_isolate_freepages(struct compact_control *cc)
total_isolated += nr_isolated;
cc->nr_freepages += nr_isolated;
list_add_tail(&page->lru, &cc->freepages[order].pages);
+ cc->freepages[order].nr_pages++;
count_compact_events(COMPACTISOLATED, nr_isolated);
} else {
/* If isolation fails, abort the search */
I will send out v3 once I rerun vm-scalability and thpcompact.
--
Best Regards,
Yan, Zi