Messages in this thread | | | Date | Wed, 7 May 2014 14:20:33 -0700 | From | Andrew Morton <> | Subject | Re: [patch v3 6/6] mm, compaction: terminate async compaction when rescheduling |
| |
On Tue, 6 May 2014 19:22:52 -0700 (PDT) David Rientjes <rientjes@google.com> wrote:
> Async compaction terminates prematurely when need_resched(), see > compact_checklock_irqsave(). This can never trigger, however, if the > cond_resched() in isolate_migratepages_range() always takes care of the > scheduling. > > If the cond_resched() actually triggers, then terminate this pageblock scan for > async compaction as well. > > .. > > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -500,8 +500,13 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc, > return 0; > } > > + if (cond_resched()) { > + /* Async terminates prematurely on need_resched() */ > + if (cc->mode == MIGRATE_ASYNC) > + return 0; > + }
Comment comments the obvious. What is less obvious is *why* we do this.
Someone please remind my why sync and async compaction use different scanning cursors?
| |