From b5a1300e1fee62b3753a107f92bce9f749fcd697 Mon Sep 17 00:00:00 2001 From: Joonsoo Kim Date: Wed, 14 May 2014 10:01:49 +1000 Subject: [PATCH] mm-compaction-cleanup-isolate_freepages-fix3 What I did here is taking end_pfn out of the loop and considering zone boundary once. After then, we can just set previous pfn to end_pfn on every iteration to move scanning window. With this change, we can remove local variable, z_end_pfn. Another things I did are removing max() operation and un-needed assignment to isolate variable. In addition, I change both the variable names, from pfn and end_pfn to block_start_pfn and block_end_pfn, respectively. They represent their meaning perfectly. Signed-off-by: Joonsoo Kim Acked-by: Vlastimil Babka Acked-by: Michal Nazarewicz Cc: Minchan Kim Cc: Mel Gorman Cc: Joonsoo Kim Cc: Bartlomiej Zolnierkiewicz Cc: Naoya Horiguchi Cc: Christoph Lameter Cc: Rik van Riel Cc: Dongjun Shin Cc: Sunghwan Yun Signed-off-by: Andrew Morton --- mm/compaction.c | 46 +++++++++++++++++++++------------------------- 1 file changed, 21 insertions(+), 25 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 6a42ee508e6c..8e501566199c 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -662,10 +662,10 @@ static void isolate_freepages(struct zone *zone, struct compact_control *cc) { struct page *page; - unsigned long pfn; /* scanning cursor */ + 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 */ - unsigned long z_end_pfn; /* zone's end pfn */ int nr_freepages = cc->nr_freepages; struct list_head *freelist = &cc->freepages; @@ -673,31 +673,33 @@ 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); /* - * Seed the value for max(next_free_pfn, pfn) updates. If no pages are - * isolated, the pfn < low_pfn check will kick in. + * If no pages are isolated, the block_start_pfn < low_pfn check + * will kick in. */ next_free_pfn = 0; - z_end_pfn = zone_end_pfn(zone); - /* * 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 @@ -706,7 +708,7 @@ static void isolate_freepages(struct zone *zone, */ cond_resched(); - if (!pfn_valid(pfn)) + if (!pfn_valid(block_start_pfn)) continue; /* @@ -716,7 +718,7 @@ 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; @@ -729,14 +731,8 @@ 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; /* @@ -744,9 +740,9 @@ 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; - next_free_pfn = max(next_free_pfn, pfn); + next_free_pfn = block_start_pfn; } } @@ -757,7 +753,7 @@ 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) + if (block_start_pfn < low_pfn) next_free_pfn = cc->migrate_pfn; cc->free_pfn = next_free_pfn; -- 2.39.5