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

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Date:	Wed, 27 Apr 2016 16:55:49 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	<linux-kernel@...r.kernel.org>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: zram: per-cpu compression streams

On Wed, Apr 27, 2016 at 04:43:35PM +0900, Sergey Senozhatsky wrote:
> 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.

Okay, I think it's worth to merge enough and see the result.
Please send formal patch which has recompression stat. ;-)

Thanks.