diff options
authorVlastimil Babka <vbabka@suse.cz>2014-05-06 12:50:03 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-06-16 13:42:53 -0700
commitee7f7615f9119c1e952a0b364ec5862f37a3ada7 (patch)
parent87c4475c903e68e494facf6ddf4c2c952b46b936 (diff)
mm/compaction: make isolate_freepages start at pageblock boundary
commit 49e068f0b73dd042c186ffa9b420a9943e90389a upstream. 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 <vbabka@suse.cz> Reported-by: Heesub Shin <heesub.shin@samsung.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Mel Gorman <mgorman@suse.de> Acked-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> Cc: Michal Nazarewicz <mina86@mina86.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Christoph Lameter <cl@linux.com> Acked-by: Rik van Riel <riel@redhat.com> Cc: Dongjun Shin <d.j.shin@samsung.com> Cc: Sunghwan Yun <sunghwan.yun@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 12 insertions, 10 deletions
diff --git a/mm/compaction.c b/mm/compaction.c
index 110daa4b3f7..fb797a32362 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -657,16 +657,20 @@ 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);
@@ -686,6 +690,7 @@ 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;
if (!pfn_valid(pfn))
@@ -713,13 +718,10 @@ 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;