lkml.org 
[lkml]   [2010]   [Jan]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 7/7] Do not compact within a preferred zone after a compaction failure
On Wed, Jan 13, 2010 at 03:28:16PM -0800, David Rientjes wrote:
> 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?
>

Yep

> >
> > 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().
>

Moved to an inline called defer_compaction()

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab


\
 
 \ /
  Last update: 2010-01-20 10:55    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site