linux-kernel - Re: zram: per-cpu compression streams

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Date:	Wed, 27 Apr 2016 16:43:35 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: zram: per-cpu compression streams

Hello,

On (04/27/16 16:29), Minchan Kim wrote:
[..]
> > the test:
> > 
> > -- 4 GB x86_64 box
> > -- zram 3GB, lzo
> > -- mem-hogger pre-faults 3GB of pages before the fio test
> > -- fio test has been modified to have 11% compression ratio (to increase the
> >                                                   chances of re-compressions)
> 
> Could you test concurrent mem hogger with fio rather than pre-fault before fio test
> in next submit?

this test will not prove anything, unfortunately. I performed it;
and it's impossible to guarantee even remotely stable results.
mem-hogger process can spend on pre-fault from 41 to 81 seconds;
so I'm quite sceptical about the actual value of this test.

> > considering buffer_compress_percentage=11, the box was under somewhat
> > heavy pressure.
> > 
> > now, the results
> 
> Yeb, Even, recompression case is fater than old but want to see more heavy memory
> pressure case and the ratio I mentioned above.

I did quite heavy testing over the last 7 days, with numerous OOM kills
and OOM panics.

	-ss