diff options
author | Vlastimil Babka <vbabka@suse.cz> | 2014-06-04 16:07:26 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-06-04 16:54:00 -0700 |
commit | c96b9e508f3d06ddb601dcc9792d62c044ab359e (patch) | |
tree | b4acb0fb4634a8fbe98968b02532b6f1b05ddaaf /mm | |
parent | 13fb44e4b0414d7e718433a49e6430d5b76bd46e (diff) | |
download | linux-c96b9e508f3d06ddb601dcc9792d62c044ab359e.tar.bz2 |
mm/compaction: cleanup isolate_freepages()
isolate_freepages() is currently somewhat hard to follow thanks to many
looks like it is related to the 'low_pfn' variable, but in fact it is not.
This patch renames the 'high_pfn' variable to a hopefully less confusing name,
and slightly changes its handling without a functional change. A comment made
obsolete by recent changes is also updated.
[akpm@linux-foundation.org: comment fixes, per Minchan]
[iamjoonsoo.kim@lge.com: cleanups]
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: 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>
Cc: Rik van Riel <riel@redhat.com>
Cc: Dongjun Shin <d.j.shin@samsung.com>
Cc: Sunghwan Yun <sunghwan.yun@samsung.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/compaction.c | 56 |
1 files changed, 27 insertions, 29 deletions
diff --git a/mm/compaction.c b/mm/compaction.c index 95f7531458f7..6010aabde28c 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -665,7 +665,10 @@ static void isolate_freepages(struct zone *zone, struct compact_control *cc) { struct page *page; - unsigned long high_pfn, low_pfn, pfn, z_end_pfn; + unsigned long block_start_pfn; /* start of current pageblock */ + unsigned long block_end_pfn; /* end of current pageblock */ + unsigned long low_pfn; /* lowest pfn scanner is able to scan */ + unsigned long next_free_pfn; /* start pfn for scaning at next round */ int nr_freepages = cc->nr_freepages; struct list_head *freelist = &cc->freepages; @@ -673,32 +676,33 @@ static void isolate_freepages(struct zone *zone, * Initialise the free scanner. The starting point is where we last * 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 pageblock boundary, because we do + * block_start_pfn -= pageblock_nr_pages in the for loop. + * For ending point, take care when isolating in last pageblock of a + * a zone which ends in the middle of a pageblock. * The low boundary is the end of the pageblock the migration scanner * is using. */ - pfn = cc->free_pfn & ~(pageblock_nr_pages-1); + block_start_pfn = cc->free_pfn & ~(pageblock_nr_pages-1); + block_end_pfn = min(block_start_pfn + pageblock_nr_pages, + zone_end_pfn(zone)); low_pfn = ALIGN(cc->migrate_pfn + 1, pageblock_nr_pages); /* - * Take care that if the migration scanner is at the end of the zone - * that the free scanner does not accidentally move to the next zone - * in the next isolation cycle. + * If no pages are isolated, the block_start_pfn < low_pfn check + * will kick in. */ - high_pfn = min(low_pfn, pfn); - - z_end_pfn = zone_end_pfn(zone); + next_free_pfn = 0; /* * Isolate free pages until enough are available to migrate the * pages on cc->migratepages. We stop searching if the migrate * and free page scanners meet or enough free pages are isolated. */ - for (; pfn >= low_pfn && cc->nr_migratepages > nr_freepages; - pfn -= pageblock_nr_pages) { + for (; block_start_pfn >= low_pfn && cc->nr_migratepages > nr_freepages; + block_end_pfn = block_start_pfn, + block_start_pfn -= pageblock_nr_pages) { unsigned long isolated; - unsigned long end_pfn; /* * This can iterate a massively long zone without finding any @@ -707,7 +711,7 @@ static void isolate_freepages(struct zone *zone, */ cond_resched(); - if (!pfn_valid(pfn)) + if (!pfn_valid(block_start_pfn)) continue; /* @@ -717,7 +721,7 @@ static void isolate_freepages(struct zone *zone, * i.e. it's possible that all pages within a zones range of * pages do not belong to a single zone. */ - page = pfn_to_page(pfn); + page = pfn_to_page(block_start_pfn); if (page_zone(page) != zone) continue; @@ -730,14 +734,8 @@ static void isolate_freepages(struct zone *zone, continue; /* Found a block suitable for isolating free pages from */ - - /* - * Take care when isolating in last pageblock of a zone which - * ends in the middle of a pageblock. - */ - end_pfn = min(pfn + pageblock_nr_pages, z_end_pfn); - isolated = isolate_freepages_block(cc, pfn, end_pfn, - freelist, false); + isolated = isolate_freepages_block(cc, block_start_pfn, + block_end_pfn, freelist, false); nr_freepages += isolated; /* @@ -745,9 +743,9 @@ static void isolate_freepages(struct zone *zone, * looking for free pages, the search will restart here as * page migration may have returned some pages to the allocator */ - if (isolated) { + if (isolated && next_free_pfn == 0) { cc->finished_update_free = true; - high_pfn = max(high_pfn, pfn); + next_free_pfn = block_start_pfn; } } @@ -758,10 +756,10 @@ static void isolate_freepages(struct zone *zone, * If we crossed the migrate scanner, we want to keep it that way * so that compact_finished() may detect this */ - if (pfn < low_pfn) - cc->free_pfn = max(pfn, zone->zone_start_pfn); - else - cc->free_pfn = high_pfn; + if (block_start_pfn < low_pfn) + next_free_pfn = cc->migrate_pfn; + + cc->free_pfn = next_free_pfn; cc->nr_freepages = nr_freepages; } |