[PATCH v3 2/4] mm: failfast mode with __GFP_NORETRY in alloc_contig_range
From: Minchan Kim <minchan@kernel.org>
Date: 2021-01-13 01:22:52
Also in:
linux-devicetree, linux-media, lkml
Subsystem:
memory management, memory management - page allocator, the rest · Maintainers:
Andrew Morton, Vlastimil Babka, Linus Torvalds
Contiguous memory allocation can be stalled due to waiting on page writeback and/or page lock which causes unpredictable delay. It's a unavoidable cost for the requestor to get *big* contiguous memory but it's expensive for *small* contiguous memory(e.g., order-4) because caller could retry the request in diffrent range where would have easy migratable pages without stalling. This patch introduce __GFP_NORETRY as compaction gfp_mask in alloc_contig_range so it will fail fast without blocking when it encounters pages needed waitting. Signed-off-by: Minchan Kim <minchan@kernel.org> --- mm/page_alloc.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5b3923db9158..ff41ceb4db51 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c@@ -8489,12 +8489,16 @@ static int __alloc_contig_migrate_range(struct compact_control *cc, unsigned int nr_reclaimed; unsigned long pfn = start; unsigned int tries = 0; + unsigned int max_tries = 5; int ret = 0; struct migration_target_control mtc = { .nid = zone_to_nid(cc->zone), .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL, }; + if (cc->alloc_contig && cc->mode == MIGRATE_ASYNC) + max_tries = 1; + migrate_prep(); while (pfn < end || !list_empty(&cc->migratepages)) {
@@ -8511,7 +8515,7 @@ static int __alloc_contig_migrate_range(struct compact_control *cc, break; } tries = 0; - } else if (++tries == 5) { + } else if (++tries == max_tries) { ret = ret < 0 ? ret : -EBUSY; break; }
@@ -8562,7 +8566,7 @@ int alloc_contig_range(unsigned long start, unsigned long end, .nr_migratepages = 0, .order = -1, .zone = page_zone(pfn_to_page(start)), - .mode = MIGRATE_SYNC, + .mode = gfp_mask & __GFP_NORETRY ? MIGRATE_ASYNC : MIGRATE_SYNC, .ignore_skip_hint = true, .no_set_skip_hint = true, .gfp_mask = current_gfp_context(gfp_mask),
--
2.30.0.284.gd98b1dd5eaa7-goog