linux-kernel - Re: [PATCH RFC] slub: reap free slabs periodically

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Date:	Tue, 14 Jun 2016 11:13:12 +0300
From:	Vladimir Davydov <vdavydov@...tuozzo.com>
To:	Christoph Lameter <cl@...ux.com>
CC:	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	<linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] slub: reap free slabs periodically

On Fri, Jun 10, 2016 at 04:32:26PM -0500, Christoph Lameter wrote:
> One reason for SLUBs creation was the 2 second scans in  SLAB which causes
> significant disruption of latency sensitive tasksk.

That's not good, indeed.

> 
> You can simply implement a reaper in userspace by running
> 
> slabinfo -s
> 
> if you have to have this.

Doing this periodically would probably hurt performance of active caches
as 'slabinfo -s' shrinks all slabs unconditionally, even if they are
being actively used. OTOH, one could trigger shrinking slabs only on
memory pressure. That would require yet another daemon tracking the
system state, but it is doable I guess.

Thanks a lot for your input, Christoph.

> 
> There is no need to duplicate SLAB problems.