On Wed, Jan 13, 2021 at 09:39:26AM +0100, David Hildenbrand wrote:
On 13.01.21 02:21, Minchan Kim wrote:
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.
s/diffrent/different/
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.
s/waitting/waiting/
Fxed both. Thanks. Let me resend once I get some review.
Michal, I appreciate if you could give an review before next revision.
Thanks!
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,I'm fine with using gfp flags (e.g., __GFP_NORETRY) as long as they don't enable other implicit behavior (e.g., move draining X to the caller) that's hard to get from the flag name.
IMHO, if we ever want to move draining to the caller, or change the behavior of alloc_contig_range() in different ways (e.g., disable PCP), we won't get around introducing a separate set of flags for alloc_contig_range().
Let's see what Michal thinks. Thanks!
-- Thanks,
David / dhildenb