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authorBaolin Wang <baolin.wang@linux.alibaba.com>2023-10-21 12:33:22 +0800
committerAndrew Morton <akpm@linux-foundation.org>2023-10-25 16:47:14 -0700
commiteebb3dabbb5cc590afe32880b5d3726d0fbf88db (patch)
tree994e65b293bb4d7cdfed5a8381800863c13bc9b6
parente5b16c862884a62c09ab60cbfc6c7b544670bf9e (diff)
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mm: migrate: record the mlocked page status to remove unnecessary lru drain
When doing compaction, I found the lru_add_drain() is an obvious hotspot when migrating pages. The distribution of this hotspot is as follows: - 18.75% compact_zone - 17.39% migrate_pages - 13.79% migrate_pages_batch - 11.66% migrate_folio_move - 7.02% lru_add_drain + 7.02% lru_add_drain_cpu + 3.00% move_to_new_folio 1.23% rmap_walk + 1.92% migrate_folio_unmap + 3.20% migrate_pages_sync + 0.90% isolate_migratepages The lru_add_drain() was added by commit c3096e6782b7 ("mm/migrate: __unmap_and_move() push good newpage to LRU") to drain the newpage to LRU immediately, to help to build up the correct newpage->mlock_count in remove_migration_ptes() for mlocked pages. However, if there are no mlocked pages are migrating, then we can avoid this lru drain operation, especailly for the heavy concurrent scenarios. So we can record the source pages' mlocked status in migrate_folio_unmap(), and only drain the lru list when the mlocked status is set in migrate_folio_move(). In addition, the page was already isolated from lru when migrating, so checking the mlocked status is stable by folio_test_mlocked() in migrate_folio_unmap(). After this patch, I can see the hotpot of the lru_add_drain() is gone: - 9.41% migrate_pages_batch - 6.15% migrate_folio_move - 3.64% move_to_new_folio + 1.80% migrate_folio_extra + 1.70% buffer_migrate_folio + 1.41% rmap_walk + 0.62% folio_add_lru + 3.07% migrate_folio_unmap Meanwhile, the compaction latency shows some improvements when running thpscale: base patched Amean fault-both-1 1131.22 ( 0.00%) 1112.55 * 1.65%* Amean fault-both-3 2489.75 ( 0.00%) 2324.15 * 6.65%* Amean fault-both-5 3257.37 ( 0.00%) 3183.18 * 2.28%* Amean fault-both-7 4257.99 ( 0.00%) 4079.04 * 4.20%* Amean fault-both-12 6614.02 ( 0.00%) 6075.60 * 8.14%* Amean fault-both-18 10607.78 ( 0.00%) 8978.86 * 15.36%* Amean fault-both-24 14911.65 ( 0.00%) 11619.55 * 22.08%* Amean fault-both-30 14954.67 ( 0.00%) 14925.66 * 0.19%* Amean fault-both-32 16654.87 ( 0.00%) 15580.31 * 6.45%* Link: https://lkml.kernel.org/r/06e9153a7a4850352ec36602df3a3a844de45698.1697859741.git.baolin.wang@linux.alibaba.com Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Reviewed-by: Zi Yan <ziy@nvidia.com> Cc: Hugh Dickins <hughd@google.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Yin Fengwei <fengwei.yin@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
-rw-r--r--mm/migrate.c48
1 files changed, 29 insertions, 19 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index 125194f5af0f..35a88334bb3c 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1027,22 +1027,28 @@ union migration_ptr {
struct anon_vma *anon_vma;
struct address_space *mapping;
};
+
+enum {
+ PAGE_WAS_MAPPED = BIT(0),
+ PAGE_WAS_MLOCKED = BIT(1),
+};
+
static void __migrate_folio_record(struct folio *dst,
- unsigned long page_was_mapped,
+ unsigned long old_page_state,
struct anon_vma *anon_vma)
{
union migration_ptr ptr = { .anon_vma = anon_vma };
dst->mapping = ptr.mapping;
- dst->private = (void *)page_was_mapped;
+ dst->private = (void *)old_page_state;
}
static void __migrate_folio_extract(struct folio *dst,
- int *page_was_mappedp,
+ int *old_page_state,
struct anon_vma **anon_vmap)
{
union migration_ptr ptr = { .mapping = dst->mapping };
*anon_vmap = ptr.anon_vma;
- *page_was_mappedp = (unsigned long)dst->private;
+ *old_page_state = (unsigned long)dst->private;
dst->mapping = NULL;
dst->private = NULL;
}
@@ -1103,7 +1109,7 @@ static int migrate_folio_unmap(new_folio_t get_new_folio,
{
struct folio *dst;
int rc = -EAGAIN;
- int page_was_mapped = 0;
+ int old_page_state = 0;
struct anon_vma *anon_vma = NULL;
bool is_lru = !__folio_test_movable(src);
bool locked = false;
@@ -1157,6 +1163,8 @@ static int migrate_folio_unmap(new_folio_t get_new_folio,
folio_lock(src);
}
locked = true;
+ if (folio_test_mlocked(src))
+ old_page_state |= PAGE_WAS_MLOCKED;
if (folio_test_writeback(src)) {
/*
@@ -1206,7 +1214,7 @@ static int migrate_folio_unmap(new_folio_t get_new_folio,
dst_locked = true;
if (unlikely(!is_lru)) {
- __migrate_folio_record(dst, page_was_mapped, anon_vma);
+ __migrate_folio_record(dst, old_page_state, anon_vma);
return MIGRATEPAGE_UNMAP;
}
@@ -1232,11 +1240,11 @@ static int migrate_folio_unmap(new_folio_t get_new_folio,
VM_BUG_ON_FOLIO(folio_test_anon(src) &&
!folio_test_ksm(src) && !anon_vma, src);
try_to_migrate(src, mode == MIGRATE_ASYNC ? TTU_BATCH_FLUSH : 0);
- page_was_mapped = 1;
+ old_page_state |= PAGE_WAS_MAPPED;
}
if (!folio_mapped(src)) {
- __migrate_folio_record(dst, page_was_mapped, anon_vma);
+ __migrate_folio_record(dst, old_page_state, anon_vma);
return MIGRATEPAGE_UNMAP;
}
@@ -1248,7 +1256,8 @@ out:
if (rc == -EAGAIN)
ret = NULL;
- migrate_folio_undo_src(src, page_was_mapped, anon_vma, locked, ret);
+ migrate_folio_undo_src(src, old_page_state & PAGE_WAS_MAPPED,
+ anon_vma, locked, ret);
migrate_folio_undo_dst(dst, dst_locked, put_new_folio, private);
return rc;
@@ -1261,12 +1270,12 @@ static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private,
struct list_head *ret)
{
int rc;
- int page_was_mapped = 0;
+ int old_page_state = 0;
struct anon_vma *anon_vma = NULL;
bool is_lru = !__folio_test_movable(src);
struct list_head *prev;
- __migrate_folio_extract(dst, &page_was_mapped, &anon_vma);
+ __migrate_folio_extract(dst, &old_page_state, &anon_vma);
prev = dst->lru.prev;
list_del(&dst->lru);
@@ -1287,10 +1296,10 @@ static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private,
* isolated from the unevictable LRU: but this case is the easiest.
*/
folio_add_lru(dst);
- if (page_was_mapped)
+ if (old_page_state & PAGE_WAS_MLOCKED)
lru_add_drain();
- if (page_was_mapped)
+ if (old_page_state & PAGE_WAS_MAPPED)
remove_migration_ptes(src, dst, false);
out_unlock_both:
@@ -1322,11 +1331,12 @@ out:
*/
if (rc == -EAGAIN) {
list_add(&dst->lru, prev);
- __migrate_folio_record(dst, page_was_mapped, anon_vma);
+ __migrate_folio_record(dst, old_page_state, anon_vma);
return rc;
}
- migrate_folio_undo_src(src, page_was_mapped, anon_vma, true, ret);
+ migrate_folio_undo_src(src, old_page_state & PAGE_WAS_MAPPED,
+ anon_vma, true, ret);
migrate_folio_undo_dst(dst, true, put_new_folio, private);
return rc;
@@ -1799,12 +1809,12 @@ out:
dst = list_first_entry(&dst_folios, struct folio, lru);
dst2 = list_next_entry(dst, lru);
list_for_each_entry_safe(folio, folio2, &unmap_folios, lru) {
- int page_was_mapped = 0;
+ int old_page_state = 0;
struct anon_vma *anon_vma = NULL;
- __migrate_folio_extract(dst, &page_was_mapped, &anon_vma);
- migrate_folio_undo_src(folio, page_was_mapped, anon_vma,
- true, ret_folios);
+ __migrate_folio_extract(dst, &old_page_state, &anon_vma);
+ migrate_folio_undo_src(folio, old_page_state & PAGE_WAS_MAPPED,
+ anon_vma, true, ret_folios);
list_del(&dst->lru);
migrate_folio_undo_dst(dst, true, put_new_folio, private);
dst = dst2;