Re: [PATCH V2] Allow compaction of unevictable pages

From: David Rientjes
Date: Mon Mar 09 2015 - 15:58:02 EST


On Mon, 9 Mar 2015, Eric B Munson wrote:

> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index f279d9c..599fb01 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -232,8 +232,6 @@ struct lruvec {
> #define ISOLATE_UNMAPPED ((__force isolate_mode_t)0x2)
> /* Isolate for asynchronous migration */
> #define ISOLATE_ASYNC_MIGRATE ((__force isolate_mode_t)0x4)
> -/* Isolate unevictable pages */
> -#define ISOLATE_UNEVICTABLE ((__force isolate_mode_t)0x8)
>
> /* LRU Isolation modes. */
> typedef unsigned __bitwise__ isolate_mode_t;
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 8c0d945..4a8ea87 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -872,8 +872,7 @@ isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
> if (!pageblock_pfn_to_page(pfn, block_end_pfn, cc->zone))
> continue;
>
> - pfn = isolate_migratepages_block(cc, pfn, block_end_pfn,
> - ISOLATE_UNEVICTABLE);
> + pfn = isolate_migratepages_block(cc, pfn, block_end_pfn, 0);
>
> /*
> * In case of fatal failure, release everything that might
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 5e8eadd..3b2a444 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1234,10 +1234,6 @@ int __isolate_lru_page(struct page *page, isolate_mode_t mode)
> if (!PageLRU(page))
> return ret;
>
> - /* Compaction should not handle unevictable pages but CMA can do so */
> - if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE))
> - return ret;
> -
> ret = -EBUSY;
>
> /*

Looks better!

I think there's one more cleanup we can do now thanks to your patch:
dropping the isolate_mode_t formal from isolate_migratepages_block()
entirely since that function can now just do

const isolate_mode_t isolate_mode =
(cc->mode == MIGRATE_ASYNC ? ISOLATE_ASYNC_MIGRATE : 0);

since we already pass in the struct compact_control and isolate_mode only
depends on MIGRATE_ASYNC or not.

If you'd like to fold that change into this patch because it's logically
allowed by it, feel free to add my enthusiastic

Acked-by: David Rientjes <rientjes@xxxxxxxxxx>

Otherwise, I'll just send a change on top of it if you don't have time.

Thanks!
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