linux-kernel - Re: [RFC 0/4] ZRAM: make it just store the high compression rate page

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Date:   Wed, 24 Aug 2016 09:29:49 +0800
From:   Hui Zhu <teawater@...il.com>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Hui Zhu <zhuhui@...omi.com>, ngupta@...are.org,
        sergey.senozhatsky.work@...il.com, Hugh Dickins <hughd@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>, acme@...nel.org,
        alexander.shishkin@...ux.intel.com,
        Andrew Morton <akpm@...ux-foundation.org>, mhocko@...e.com,
        hannes@...xchg.org, mgorman@...hsingularity.net, vbabka@...e.cz,
        redkoi@...tuozzo.com, luto@...nel.org,
        kirill.shutemov@...ux.intel.com, geliangtang@....com,
        baiyaowei@...s.chinamobile.com, dan.j.williams@...el.com,
        vdavydov@...tuozzo.com, aarcange@...hat.com, dvlasenk@...hat.com,
        jmarchan@...hat.com, koct9i@...il.com, yang.shi@...aro.org,
        dave.hansen@...ux.intel.com, vkuznets@...hat.com,
        vitalywool@...il.com, ross.zwisler@...ux.intel.com,
        Thomas Gleixner <tglx@...utronix.de>,
        kwapulinski.piotr@...il.com, axboe@...com, mchristi@...hat.com,
        Joe Perches <joe@...ches.com>, namit@...are.com,
        Rik van Riel <riel@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [RFC 0/4] ZRAM: make it just store the high compression rate page

Hi Minchan,

On Wed, Aug 24, 2016 at 9:04 AM, Minchan Kim <minchan@...nel.org> wrote:
> Hi Hui,
>
> On Mon, Aug 22, 2016 at 04:25:05PM +0800, Hui Zhu wrote:
>> Current ZRAM just can store all pages even if the compression rate
>> of a page is really low.  So the compression rate of ZRAM is out of
>> control when it is running.
>> In my part, I did some test and record with ZRAM.  The compression rate
>> is about 40%.
>>
>> This series of patches make ZRAM can just store the page that the
>> compressed size is smaller than a value.
>> With these patches, I set the value to 2048 and did the same test with
>> before.  The compression rate is about 20%.  The times of lowmemorykiller
>> also decreased.
>
> I have an interest about the feature for a long time but didn't work on it
> because I didn't have a good idea to implment it with generic approach
> without layer violation. I will look into this after handling urgent works.
>
> Thanks.

That will be great.  Thanks.

Best,
Hui