diff options
author | Vlastimil Babka <[email protected]> | 2014-05-06 12:50:03 -0700 |
---|---|---|
committer | Linus Torvalds <[email protected]> | 2014-05-06 13:04:59 -0700 |
commit | 49e068f0b73dd042c186ffa9b420a9943e90389a (patch) | |
tree | defb673f5ac84bdc9824fb3200fee1933b28aea9 | |
parent | 0e3b7e5402cbec4cee58895a00945356ee26a720 (diff) |
mm/compaction: make isolate_freepages start at pageblock boundary
The compaction freepage scanner implementation in isolate_freepages()
starts by taking the current cc->free_pfn value as the first pfn. In a
for loop, it scans from this first pfn to the end of the pageblock, and
then subtracts pageblock_nr_pages from the first pfn to obtain the first
pfn for the next for loop iteration.
This means that when cc->free_pfn starts at offset X rather than being
aligned on pageblock boundary, the scanner will start at offset X in all
scanned pageblock, ignoring potentially many free pages. Currently this
can happen when
a) zone's end pfn is not pageblock aligned, or
b) through zone->compact_cached_free_pfn with CONFIG_HOLES_IN_ZONE
enabled and a hole spanning the beginning of a pageblock
This patch fixes the problem by aligning the initial pfn in
isolate_freepages() to pageblock boundary. This also permits replacing
the end-of-pageblock alignment within the for loop with a simple
pageblock_nr_pages increment.
Signed-off-by: Vlastimil Babka <[email protected]>
Reported-by: Heesub Shin <[email protected]>
Acked-by: Minchan Kim <[email protected]>
Cc: Mel Gorman <[email protected]>
Acked-by: Joonsoo Kim <[email protected]>
Cc: Bartlomiej Zolnierkiewicz <[email protected]>
Cc: Michal Nazarewicz <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Christoph Lameter <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Cc: Dongjun Shin <[email protected]>
Cc: Sunghwan Yun <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
-rw-r--r-- | mm/compaction.c | 22 |
1 files changed, 12 insertions, 10 deletions
diff --git a/mm/compaction.c b/mm/compaction.c index 37f976287068..627dc2e4320f 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -671,16 +671,20 @@ static void isolate_freepages(struct zone *zone, struct compact_control *cc) { struct page *page; - unsigned long high_pfn, low_pfn, pfn, z_end_pfn, end_pfn; + unsigned long high_pfn, low_pfn, pfn, z_end_pfn; int nr_freepages = cc->nr_freepages; struct list_head *freelist = &cc->freepages; /* * Initialise the free scanner. The starting point is where we last - * scanned from (or the end of the zone if starting). The low point - * is the end of the pageblock the migration scanner is using. + * successfully isolated from, zone-cached value, or the end of the + * zone when isolating for the first time. We need this aligned to + * the pageblock boundary, because we do pfn -= pageblock_nr_pages + * in the for loop. + * The low boundary is the end of the pageblock the migration scanner + * is using. */ - pfn = cc->free_pfn; + pfn = cc->free_pfn & ~(pageblock_nr_pages-1); low_pfn = ALIGN(cc->migrate_pfn + 1, pageblock_nr_pages); /* @@ -700,6 +704,7 @@ static void isolate_freepages(struct zone *zone, for (; pfn >= low_pfn && cc->nr_migratepages > nr_freepages; pfn -= pageblock_nr_pages) { unsigned long isolated; + unsigned long end_pfn; /* * This can iterate a massively long zone without finding any @@ -734,13 +739,10 @@ static void isolate_freepages(struct zone *zone, isolated = 0; /* - * As pfn may not start aligned, pfn+pageblock_nr_page - * may cross a MAX_ORDER_NR_PAGES boundary and miss - * a pfn_valid check. Ensure isolate_freepages_block() - * only scans within a pageblock + * Take care when isolating in last pageblock of a zone which + * ends in the middle of a pageblock. */ - end_pfn = ALIGN(pfn + 1, pageblock_nr_pages); - end_pfn = min(end_pfn, z_end_pfn); + end_pfn = min(pfn + pageblock_nr_pages, z_end_pfn); isolated = isolate_freepages_block(cc, pfn, end_pfn, freelist, false); nr_freepages += isolated; |