linux-kernel - Re: [PATCH 0/3] zsmalloc: small compaction improvements

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Message-ID: <20150715111625.GC3998@swordfish>
Date:	Wed, 15 Jul 2015 20:16:25 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] zsmalloc: small compaction improvements

On (07/15/15 09:24), Minchan Kim wrote:
> On Wed, Jul 15, 2015 at 09:21:06AM +0900, Sergey Senozhatsky wrote:
> > On (07/15/15 01:52), Minchan Kim wrote:
> > > > alrighty... again...
> > > > 
> > > > > > 
> > > > > > /sys/block/zram<id>/compact is a black box. We provide it, we don't
> > > > > > throttle it in the kernel, and user space is absolutely clueless when
> > > > > > it invokes compaction. From some remote (or alternative) point of
> > > > > 
> > > > > But we have zs_can_compact so it can effectively skip the class if it
> > > > > is not proper class.
> > > > 
> > > > user triggered compaction can compact too much.
> > > > in its current state triggering a compaction from user space is like
> > > > playing a lottery or a russian roulette.
> > > 
> > > We were on different page.
> > 
> > > I thought the motivation from this patchset is to prevent compaction
> > > overhead by frequent user-driven compaction request because user
> > > don't know how they can get free pages by compaction so they should
> > > ask compact frequently with blind.
> > 
> > this is exactly the motivation for this patchset. seriously.
> 
> User should rely on the auto-compaction.

yep, which will be available in 5-6 months... right behind the corner.

	-ss
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