The patch titled
Subject: mm, compaction: abort free scanner if split fails
has been removed from the -mm tree. Its filename was
mm-compaction-abort-free-scanner-if-split-fails.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: David Rientjes <rientjes@xxxxxxxxxx>
Subject: mm, compaction: abort free scanner if split fails
If the memory compaction free scanner cannot successfully split a free
page (only possible due to per-zone low watermark), terminate the free
scanner rather than continuing to scan memory needlessly. If the
watermark is insufficient for a free page of order <= cc->order, then
terminate the scanner since all future splits will also likely fail.
This prevents the compaction freeing scanner from scanning all memory on
very large zones (very noticeable for zones > 128GB, for instance) when
all splits will likely fail while holding zone->lock.
compaction_alloc() iterating a 128GB zone has been benchmarked to take
over 400ms on some systems whereas any free page isolated and ready to
be split ends up failing in split_free_page() because of the low
watermark check and thus the iteration continues.
The next time compaction occurs, the freeing scanner will likely start
at the end of the zone again since no success was made previously and
we get the same lengthy iteration until the zone is brought above the
low watermark. All thp page faults can take >400ms in such a state
without this fix.
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1606211820350.97086@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 39 +++++++++++++++++++++------------------
1 file changed, 21 insertions(+), 18 deletions(-)
diff -puN mm/compaction.c~mm-compaction-abort-free-scanner-if-split-fails mm/compaction.c
--- a/mm/compaction.c~mm-compaction-abort-free-scanner-if-split-fails
+++ a/mm/compaction.c
@@ -441,25 +441,23 @@ static unsigned long isolate_freepages_b
/* Found a free page, break it into order-0 pages */
isolated = split_free_page(page);
+ if (!isolated)
+ break;
+
total_isolated += isolated;
+ cc->nr_freepages += isolated;
for (i = 0; i < isolated; i++) {
list_add(&page->lru, freelist);
page++;
}
-
- /* If a page was split, advance to the end of it */
- if (isolated) {
- cc->nr_freepages += isolated;
- if (!strict &&
- cc->nr_migratepages <= cc->nr_freepages) {
- blockpfn += isolated;
- break;
- }
-
- blockpfn += isolated - 1;
- cursor += isolated - 1;
- continue;
+ if (!strict && cc->nr_migratepages <= cc->nr_freepages) {
+ blockpfn += isolated;
+ break;
}
+ /* Advance to the end of split page */
+ blockpfn += isolated - 1;
+ cursor += isolated - 1;
+ continue;
isolate_fail:
if (strict)
@@ -469,6 +467,9 @@ isolate_fail:
}
+ if (locked)
+ spin_unlock_irqrestore(&cc->zone->lock, flags);
+
/*
* There is a tiny chance that we have read bogus compound_order(),
* so be careful to not go outside of the pageblock.
@@ -490,9 +491,6 @@ isolate_fail:
if (strict && blockpfn < end_pfn)
total_isolated = 0;
- if (locked)
- spin_unlock_irqrestore(&cc->zone->lock, flags);
-
/* Update the pageblock-skip if the whole pageblock was scanned */
if (blockpfn == end_pfn)
update_pageblock_skip(cc, valid_page, total_isolated, false);
@@ -1011,6 +1009,7 @@ static void isolate_freepages(struct com
block_end_pfn = block_start_pfn,
block_start_pfn -= pageblock_nr_pages,
isolate_start_pfn = block_start_pfn) {
+ unsigned long isolated;
/*
* This can iterate a massively long zone without finding any
@@ -1035,8 +1034,12 @@ static void isolate_freepages(struct com
continue;
/* Found a block suitable for isolating free pages from. */
- isolate_freepages_block(cc, &isolate_start_pfn,
- block_end_pfn, freelist, false);
+ isolated = isolate_freepages_block(cc, &isolate_start_pfn,
+ block_end_pfn, freelist, false);
+ /* If isolation failed early, do not continue needlessly */
+ if (!isolated && isolate_start_pfn < block_end_pfn &&
+ cc->nr_migratepages > cc->nr_freepages)
+ break;
/*
* If we isolated enough freepages, or aborted due to async
_
Patches currently in -mm which might be from rientjes@xxxxxxxxxx are
mm-compaction-split-freepages-without-holding-the-zone-lock-fix.patch
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