On Fri, Feb 19, 2010 at 3:02 AM, Mel Gorman <mel@xxxxxxxxx> 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@xxxxxxxxx>
> Acked-by: Rik van Riel <riel@xxxxxxxxxx>
> ---
> 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 6a2eefd..1cf95e2 100644
> --- a/include/linux/compaction.h
> +++ b/include/linux/compaction.h
> @@ -1,13 +1,25 @@
> #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_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 d7f7236..0ea7a38 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 02579c2..c7c73bb 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;
> };
>
> @@ -298,10 +300,31 @@ 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;
Where do we set cc->order = -1?
Sorry but I can't find it.
--
Kind regards,
Minchan Kim
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