linux-kernel - Re: [RFC][PATCHv3 3/7] zsmalloc: always keep per-class stats

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Message-ID: <20150629064029.GA13179@bbox>
Date:	Mon, 29 Jun 2015 15:40:29 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [RFC][PATCHv3 3/7] zsmalloc: always keep per-class stats

On Thu, Jun 18, 2015 at 08:46:40PM +0900, Sergey Senozhatsky wrote:
> Always account per-class `zs_size_stat' stats. This data will
> help us make better decisions during compaction. We are especially
> interested in OBJ_ALLOCATED and OBJ_USED, which can tell us if
> class compaction will result in any memory gain.
> 
> For instance, we know the number of allocated objects in the class,
> the number of objects being used (so we also know how many objects
> are not used) and the number of objects per-page. So we can ensure
> if we have enough unused objects to form at least one ZS_EMPTY
> zspage during compaction.
> 
> We calculate this value on per-class basis so we can calculate a
> total number of zspages that can be released. Which is exactly what
> a shrinker wants to know.
> 
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Acked-by: Minchan Kim <minchan@...nel.org>

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