linux-kernel - Re: [RFC][PATCH v3 2/5] mm/zsmalloc: remove shrinker compaction callbacks

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Message-ID: <20160314074523.GB542@swordfish>
Date:	Mon, 14 Mar 2016 16:45:23 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Joonsoo Kim <js1304@...il.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [RFC][PATCH v3 2/5] mm/zsmalloc: remove shrinker compaction
 callbacks

On (03/14/16 15:32), Minchan Kim wrote:
> On Thu, Mar 03, 2016 at 11:46:00PM +0900, Sergey Senozhatsky wrote:
> > Do not register shrinker compaction callbacks anymore, since
> > now we shedule class compaction work each time its fragmentation
> > value goes above the watermark.
> 
> I suggested to remove shrinker compaction but while I review your
> first patch in this thread, I thought we need upper-bound to
> compact zspage so background work can bail out for latency easily.
> IOW, the work could give up the job. In such case, we might need
> fall-back scheme to continue the job. And I think that could be
> a shrinker.
> 
> What do you think?

wouldn't this unnecessarily complicate the whole thing? we would
have
 a) a compaction that can be triggered by used space
 b) a compaction from zs_free() that can bail out
 c) a compaction triggered by the shrinker.

all 3 three can run simultaneously.


_if_ we can keep every class below its watermark, we can reduce the
need of "c)".

	-ss