On Wed, 4 Jun 2014, Vlastimil Babka wrote: > diff --git a/mm/compaction.c b/mm/compaction.c > index f0fd4b5..27c73d7 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -332,6 +332,16 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, > goto isolate_fail; > > /* > + * If we already hold the lock, we can skip some rechecking. > + * Note that if we hold the lock now, checked_pageblock was > + * already set in some previous iteration (or strict is true), > + * so it is correct to skip the suitable migration target > + * recheck as well. > + */ > + if (locked) > + goto skip_recheck; > + > + /* > * The zone lock must be held to isolate freepages. > * Unfortunately this is a very coarse lock and can be > * heavily contended if there are parallel allocations > @@ -339,9 +349,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, > * spin on the lock and we acquire the lock as late as > * possible. > */ > - if (!locked) > - locked = compact_trylock_irqsave(&cc->zone->lock, > - &flags, cc); > + locked = compact_trylock_irqsave(&cc->zone->lock, &flags, cc); > if (!locked) > break; > > @@ -361,6 +369,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, > if (!PageBuddy(page)) > goto isolate_fail; > > +skip_recheck: > /* Found a free page, break it into order-0 pages */ > isolated = split_free_page(page); > total_isolated += isolated; This doesn't apply cleanly, you probably need Andrew's "mm/compaction.c:isolate_freepages_block(): small tuneup"? Rebasing the series on -mm would probably be best. > @@ -671,10 +680,11 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc, > page_count(page) > page_mapcount(page)) > continue; > > - /* If the lock is not held, try to take it */ > - if (!locked) > - locked = compact_trylock_irqsave(&zone->lru_lock, > - &flags, cc); > + /* If we already hold the lock, we can skip some rechecking */ > + if (locked) > + goto skip_recheck; > + > + locked = compact_trylock_irqsave(&zone->lru_lock, &flags, cc); > if (!locked) > break; > > @@ -686,6 +696,7 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc, > continue; > } > > +skip_recheck: > lruvec = mem_cgroup_page_lruvec(page, zone); > > /* Try isolate the page */ Looks good. I wonder how the lock-taking and the rechecks would look nested in a "if (!locked)" clause and whether that would be cleaner (and avoid the gotos), but I assume you already looked at that. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>