linux-kernel - Re: [PATCH] mm/zsmalloc: add trace events for zs

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Date:	Wed, 8 Jun 2016 23:10:58 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Ganesh Mahendran <opensource.ganesh@...il.com>
Cc:	Minchan Kim <minchan@...nel.org>, Linux-MM <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nitin Gupta <ngupta@...are.org>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	rostedt@...dmis.org, mingo@...hat.com
Subject: Re: [PATCH] mm/zsmalloc: add trace events for zs_compact

Hello,

On (06/08/16 14:39), Ganesh Mahendran wrote:
> >> > On Tue, Jun 07, 2016 at 04:56:44PM +0800, Ganesh Mahendran wrote:
> >> >> Currently zsmalloc is widely used in android device.
> >> >> Sometimes, we want to see how frequently zs_compact is
> >> >> triggered or how may pages freed by zs_compact(), or which
> >> >> zsmalloc pool is compacted.
> >> >>
> >> >> Most of the time, user can get the brief information from
> >> >> trace_mm_shrink_slab_[start | end], but in some senario,
> >> >> they do not use zsmalloc shrinker, but trigger compaction manually.
> >> >> So add some trace events in zs_compact is convenient. Also we
> >> >> can add some zsmalloc specific information(pool name, total compact
> >> >> pages, etc) in zsmalloc trace.
> >> >
> >> > Sorry, I cannot understand what's the problem now and what you want to
> >> > solve. Could you elaborate it a bit?
> >> >
> >> > Thanks.
> >>
> >> We have backported the zs_compact() to our product(kernel 3.18).
> >> It is usefull for a longtime running device.
> >> But there is not a convenient way to get the detailed information
> >> of zs_comapct() which is usefull for  performance optimization.
> >> Information about how much time zs_compact used, which pool is
> >> compacted, how many page freed, etc.

sorry, couldn't check my email earlier.

zs_compact() is just one of the N sites that are getting called by
the shrinker; optimization here will "solve" only 1/N of the problems.
are there any trace events in any other shrinker callbacks?


why trace_mm_shrink_slab_start()/trace_mm_shrink_slab_end()/etc. don't work you?

	-ss