diff options
author | Wonhyuk Yang <vvghjk1234@gmail.com> | 2021-02-24 12:09:36 -0800 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-03-04 12:15:14 +0100 |
commit | ae3f6316202101395c4780670b28243977db04f3 (patch) | |
tree | d53853f125e33357f525d0d5489b72ae4b3c455f /mm | |
parent | 8ae648874a9c98acf349020a00bd47e897f058b2 (diff) |
mm/compaction: fix misbehaviors of fast_find_migrateblock()
[ Upstream commit 15d28d0d11609c7a4f217b3d85e26456d9beb134 ]
In the fast_find_migrateblock(), it iterates ocer the freelist to find the
proper pageblock. But there are some misbehaviors.
First, if the page we found is equal to cc->migrate_pfn, it is considered
that we didn't find a suitable pageblock. Secondly, if the loop was
terminated because order is less than PAGE_ALLOC_COSTLY_ORDER, it could be
considered that we found a suitable one. Thirdly, if the skip bit is set
on the page block and we goto continue, it doesn't check nr_scanned.
Fourthly, if the page block's skip bit is set, it checks that page block
is the last of list, which is unnecessary.
Link: https://lkml.kernel.org/r/20210128130411.6125-1-vvghjk1234@gmail.com
Fixes: 70b44595eafe9 ("mm, compaction: use free lists to quickly locate a migration source")
Signed-off-by: Wonhyuk Yang <vvghjk1234@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/compaction.c | 27 |
1 files changed, 12 insertions, 15 deletions
diff --git a/mm/compaction.c b/mm/compaction.c index 190ccdaa6c19..2135c32efe8b 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1702,6 +1702,7 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc) unsigned long pfn = cc->migrate_pfn; unsigned long high_pfn; int order; + bool found_block = false; /* Skip hints are relied on to avoid repeats on the fast search */ if (cc->ignore_skip_hint) @@ -1744,7 +1745,7 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc) high_pfn = pageblock_start_pfn(cc->migrate_pfn + distance); for (order = cc->order - 1; - order >= PAGE_ALLOC_COSTLY_ORDER && pfn == cc->migrate_pfn && nr_scanned < limit; + order >= PAGE_ALLOC_COSTLY_ORDER && !found_block && nr_scanned < limit; order--) { struct free_area *area = &cc->zone->free_area[order]; struct list_head *freelist; @@ -1759,7 +1760,11 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc) list_for_each_entry(freepage, freelist, lru) { unsigned long free_pfn; - nr_scanned++; + if (nr_scanned++ >= limit) { + move_freelist_tail(freelist, freepage); + break; + } + free_pfn = page_to_pfn(freepage); if (free_pfn < high_pfn) { /* @@ -1768,12 +1773,8 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc) * the list assumes an entry is deleted, not * reordered. */ - if (get_pageblock_skip(freepage)) { - if (list_is_last(freelist, &freepage->lru)) - break; - + if (get_pageblock_skip(freepage)) continue; - } /* Reorder to so a future search skips recent pages */ move_freelist_tail(freelist, freepage); @@ -1781,15 +1782,10 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc) update_fast_start_pfn(cc, free_pfn); pfn = pageblock_start_pfn(free_pfn); cc->fast_search_fail = 0; + found_block = true; set_pageblock_skip(freepage); break; } - - if (nr_scanned >= limit) { - cc->fast_search_fail++; - move_freelist_tail(freelist, freepage); - break; - } } spin_unlock_irqrestore(&cc->zone->lock, flags); } @@ -1800,9 +1796,10 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc) * If fast scanning failed then use a cached entry for a page block * that had free pages as the basis for starting a linear scan. */ - if (pfn == cc->migrate_pfn) + if (!found_block) { + cc->fast_search_fail++; pfn = reinit_migrate_pfn(cc); - + } return pfn; } |