Hi Rik,
On Wed, Jul 11, 2012 at 04:18:00PM -0400, Rik van Riel wrote:
> This patch makes the comment for cc->wrapped longer, explaining
> what is really going on. It also incorporates the comment fix
> pointed out by Minchan.
>
> Additionally, Minchan found that, when no pages get isolated,
> high_pte could be a value that is much lower than desired,
s/high_pte/high_pfn
> which might potentially cause compaction to skip a range of
> pages.
>
> Only assign zone->compact_cache_free_pfn if we actually
> isolated free pages for compaction.
>
> Split out the calculation to get the start of the last page
> block in a zone into its own, commented function.
>
> Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
> ---
> include/linux/mmzone.h | 2 +-
> mm/compaction.c | 30 ++++++++++++++++++++++--------
> mm/internal.h | 6 +++++-
> 3 files changed, 28 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index e629594..e957fa1 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -370,7 +370,7 @@ struct zone {
> spinlock_t lock;
> int all_unreclaimable; /* All pages pinned */
> #if defined CONFIG_COMPACTION || defined CONFIG_CMA
> - /* pfn where the last order > 0 compaction isolated free pages */
> + /* pfn where the last incremental compaction isolated free pages */
> unsigned long compact_cached_free_pfn;
> #endif
> #ifdef CONFIG_MEMORY_HOTPLUG
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 2668b77..3812c3e 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -472,10 +472,11 @@ static void isolate_freepages(struct zone *zone,
> * looking for free pages, the search will restart here as
> * page migration may have returned some pages to the allocator
> */
> - if (isolated)
> + if (isolated) {
> high_pfn = max(high_pfn, pfn);
> - if (cc->order > 0)
> - zone->compact_cached_free_pfn = high_pfn;
> + if (cc->order > 0)
> + zone->compact_cached_free_pfn = high_pfn;
> + }
> }
>
> /* split_free_page does not map the pages */
> @@ -569,6 +570,21 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
> return ISOLATE_SUCCESS;
> }
>
> +/*
> + * Returns the start pfn of the laste page block in a zone.
s/laste/last/
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