Re: [PATCH 10/11] Direct compact when a high-order allocation fails

[Minchan Kim <minchan.kim@gmail.com>]

On Wed, Mar 24, 2010 at 8:59 PM, Minchan Kim <minchan.kim@gmail.com> wrote:
> On Wed, Mar 24, 2010 at 8:11 PM, Mel Gorman <mel@csn.ul.ie> wrote:
>> On Wed, Mar 24, 2010 at 08:10:40AM +0900, Minchan Kim wrote:
>>> Hi, Mel.
>>>
>>> On Tue, Mar 23, 2010 at 9:25 PM, Mel Gorman <mel@csn.ul.ie> wrote:
>>> > Ordinarily when a high-order allocation fails, direct reclaim is entered to
>>> > free pages to satisfy the allocation.  With this patch, it is determined if
>>> > an allocation failed due to external fragmentation instead of low memory
>>> > and if so, the calling process will compact until a suitable page is
>>> > freed. Compaction by moving pages in memory is considerably cheaper than
>>> > paging out to disk and works where there are locked pages or no swap. If
>>> > compaction fails to free a page of a suitable size, then reclaim will
>>> > still occur.
>>> >
>>> > Direct compaction returns as soon as possible. As each block is compacted,
>>> > it is checked if a suitable page has been freed and if so, it returns.
>>> >
>>> > Signed-off-by: Mel Gorman <mel@csn.ul.ie>
>>> > Acked-by: Rik van Riel <riel@redhat.com>
>>> > ---
>>> >  include/linux/compaction.h |   16 +++++-
>>> >  include/linux/vmstat.h     |    1 +
>>> >  mm/compaction.c            |  118 ++++++++++++++++++++++++++++++++++++++++++++
>>> >  mm/page_alloc.c            |   26 ++++++++++
>>> >  mm/vmstat.c                |   15 +++++-
>>> >  5 files changed, 172 insertions(+), 4 deletions(-)
>>> >
>>> > diff --git a/include/linux/compaction.h b/include/linux/compaction.h
>>> > index c94890b..b851428 100644
>>> > --- a/include/linux/compaction.h
>>> > +++ b/include/linux/compaction.h
>>> > @@ -1,14 +1,26 @@
>>> >  #ifndef _LINUX_COMPACTION_H
>>> >  #define _LINUX_COMPACTION_H
>>> >
>>> > -/* Return values for compact_zone() */
>>> > +/* Return values for compact_zone() and try_to_compact_pages() */
>>> >  #define COMPACT_INCOMPLETE     0
>>> > -#define COMPACT_COMPLETE       1
>>> > +#define COMPACT_PARTIAL                1
>>> > +#define COMPACT_COMPLETE       2
>>> >
>>> >  #ifdef CONFIG_COMPACTION
>>> >  extern int sysctl_compact_memory;
>>> >  extern int sysctl_compaction_handler(struct ctl_table *table, int write,
>>> >                        void __user *buffer, size_t *length, loff_t *ppos);
>>> > +
>>> > +extern int fragmentation_index(struct zone *zone, unsigned int order);
>>> > +extern unsigned long try_to_compact_pages(struct zonelist *zonelist,
>>> > +                       int order, gfp_t gfp_mask, nodemask_t *mask);
>>> > +#else
>>> > +static inline unsigned long try_to_compact_pages(struct zonelist *zonelist,
>>> > +                       int order, gfp_t gfp_mask, nodemask_t *nodemask)
>>> > +{
>>> > +       return COMPACT_INCOMPLETE;
>>> > +}
>>> > +
>>> >  #endif /* CONFIG_COMPACTION */
>>> >
>>> >  #if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
>>> > diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
>>> > index 56e4b44..b4b4d34 100644
>>> > --- a/include/linux/vmstat.h
>>> > +++ b/include/linux/vmstat.h
>>> > @@ -44,6 +44,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
>>> >                KSWAPD_SKIP_CONGESTION_WAIT,
>>> >                PAGEOUTRUN, ALLOCSTALL, PGROTATED,
>>> >                COMPACTBLOCKS, COMPACTPAGES, COMPACTPAGEFAILED,
>>> > +               COMPACTSTALL, COMPACTFAIL, COMPACTSUCCESS,
>>> >  #ifdef CONFIG_HUGETLB_PAGE
>>> >                HTLB_BUDDY_PGALLOC, HTLB_BUDDY_PGALLOC_FAIL,
>>> >  #endif
>>> > diff --git a/mm/compaction.c b/mm/compaction.c
>>> > index 8df6e3d..6688700 100644
>>> > --- a/mm/compaction.c
>>> > +++ b/mm/compaction.c
>>> > @@ -34,6 +34,8 @@ struct compact_control {
>>> >        unsigned long nr_anon;
>>> >        unsigned long nr_file;
>>> >
>>> > +       unsigned int order;             /* order a direct compactor needs */
>>> > +       int migratetype;                /* MOVABLE, RECLAIMABLE etc */
>>> >        struct zone *zone;
>>> >  };
>>> >
>>> > @@ -301,10 +303,31 @@ static void update_nr_listpages(struct compact_control *cc)
>>> >  static inline int compact_finished(struct zone *zone,
>>> >                                                struct compact_control *cc)
>>> >  {
>>> > +       unsigned int order;
>>> > +       unsigned long watermark = low_wmark_pages(zone) + (1 << cc->order);
>>> > +
>>> >        /* Compaction run completes if the migrate and free scanner meet */
>>> >        if (cc->free_pfn <= cc->migrate_pfn)
>>> >                return COMPACT_COMPLETE;
>>> >
>>> > +       /* Compaction run is not finished if the watermark is not met */
>>> > +       if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
>>> > +               return COMPACT_INCOMPLETE;
>>> > +
>>> > +       if (cc->order == -1)
>>> > +               return COMPACT_INCOMPLETE;
>>> > +
>>> > +       /* Direct compactor: Is a suitable page free? */
>>> > +       for (order = cc->order; order < MAX_ORDER; order++) {
>>> > +               /* Job done if page is free of the right migratetype */
>>> > +               if (!list_empty(&zone->free_area[order].free_list[cc->migratetype]))
>>> > +                       return COMPACT_PARTIAL;
>>> > +
>>> > +               /* Job done if allocation would set block type */
>>> > +               if (order >= pageblock_order && zone->free_area[order].nr_free)
>>> > +                       return COMPACT_PARTIAL;
>>> > +       }
>>> > +
>>> >        return COMPACT_INCOMPLETE;
>>> >  }
>>> >
>>> > @@ -348,6 +371,101 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
>>> >        return ret;
>>> >  }
>>> >
>>> > +static inline unsigned long compact_zone_order(struct zone *zone,
>>> > +                                               int order, gfp_t gfp_mask)
>>> > +{
>>> > +       struct compact_control cc = {
>>> > +               .nr_freepages = 0,
>>> > +               .nr_migratepages = 0,
>>> > +               .order = order,
>>> > +               .migratetype = allocflags_to_migratetype(gfp_mask),
>>> > +               .zone = zone,
>>> > +       };
>>> > +       INIT_LIST_HEAD(&cc.freepages);
>>> > +       INIT_LIST_HEAD(&cc.migratepages);
>>> > +
>>> > +       return compact_zone(zone, &cc);
>>> > +}
>>> > +
>>> > +/**
>>> > + * try_to_compact_pages - Direct compact to satisfy a high-order allocation
>>> > + * @zonelist: The zonelist used for the current allocation
>>> > + * @order: The order of the current allocation
>>> > + * @gfp_mask: The GFP mask of the current allocation
>>> > + * @nodemask: The allowed nodes to allocate from
>>> > + *
>>> > + * This is the main entry point for direct page compaction.
>>> > + */
>>> > +unsigned long try_to_compact_pages(struct zonelist *zonelist,
>>> > +                       int order, gfp_t gfp_mask, nodemask_t *nodemask)
>>> > +{
>>> > +       enum zone_type high_zoneidx = gfp_zone(gfp_mask);
>>> > +       int may_enter_fs = gfp_mask & __GFP_FS;
>>> > +       int may_perform_io = gfp_mask & __GFP_IO;
>>> > +       unsigned long watermark;
>>> > +       struct zoneref *z;
>>> > +       struct zone *zone;
>>> > +       int rc = COMPACT_INCOMPLETE;
>>> > +
>>> > +       /* Check whether it is worth even starting compaction */
>>> > +       if (order == 0 || !may_enter_fs || !may_perform_io)
>>> > +               return rc;
>>> > +
>>> > +       /*
>>> > +        * We will not stall if the necessary conditions are not met for
>>> > +        * migration but direct reclaim seems to account stalls similarly
>>> > +        */

Then, Let's remove this comment.


-- 
Kind regards,
Minchan Kim

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