linux-kernel - Re: [PATCH V2] Allow compaction of unevictable pages

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Date:	Mon, 9 Mar 2015 12:57:54 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Eric B Munson <emunson@...mai.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Christoph Lameter <cl@...ux.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] Allow compaction of unevictable pages

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@...gle.com>

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

Thanks!
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