Messages in this thread | | | Date | Wed, 13 Jan 2010 15:28:16 -0800 (PST) | From | David Rientjes <> | Subject | Re: [PATCH 7/7] Do not compact within a preferred zone after a compaction failure |
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On Wed, 6 Jan 2010, Mel Gorman wrote:
> The fragmentation index may indicate that a failure it due to external > fragmentation, a compaction run complete and an allocation failure still > fail. There are two obvious reasons as to why > > o Page migration cannot move all pages so fragmentation remains > o A suitable page may exist but watermarks are not met > > In the event of compaction and allocation failure, this patch prevents > compaction happening for a short interval. It's only recorded on the > preferred zone but that should be enough coverage. This could have been > implemented similar to the zonelist_cache but the increased size of the > zonelist did not appear to be justified. > > Signed-off-by: Mel Gorman <mel@csn.ul.ie> > --- > include/linux/mmzone.h | 7 +++++++ > mm/page_alloc.c | 15 ++++++++++++++- > 2 files changed, 21 insertions(+), 1 deletions(-) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 30fe668..1d6ccbe 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -328,6 +328,13 @@ struct zone { > unsigned long *pageblock_flags; > #endif /* CONFIG_SPARSEMEM */ > > +#ifdef CONFIG_MIGRATION > + /* > + * If a compaction fails, do not try compaction again until > + * jiffies is after the value of compact_resume > + */ > + unsigned long compact_resume; > +#endif
CONFIG_COMPACTION?
> > ZONE_PADDING(_pad1_) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 7275afb..9c86606 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1729,7 +1729,7 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order, > cond_resched(); > > /* Try memory compaction for high-order allocations before reclaim */ > - if (order) { > + if (order && time_after(jiffies, preferred_zone->compact_resume)) { > *did_some_progress = try_to_compact_pages(zonelist, > order, gfp_mask, nodemask); > if (*did_some_progress != COMPACT_INCOMPLETE) { > @@ -1748,6 +1748,19 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order, > * but not enough to satisfy watermarks. > */ > count_vm_event(COMPACTFAIL); > + > + /* > + * On failure, avoid compaction for a short time. > + * XXX: This is very unsatisfactory. The failure > + * to compact has nothing to do with time > + * and everything to do with the requested > + * order, the number of free pages and > + * watermarks. How to wait on that is more > + * unclear, but the answer would apply to > + * other areas where the VM waits based on > + * time. > + */ > + preferred_zone->compact_resume = jiffies + HZ/50; > } > } >
This will need to be moved to (another) inline function dependent on CONFIG_COMPACTION since we don't have zone->compact_resume without it; it's probably better to seperate the function out rather than add #ifdef's within __alloc_pages_direct_reclaim().
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