linux-kernel - Re: [PATCH] mm: extend zero pages to same element pages for zram

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Date:   Wed, 25 Jan 2017 13:18:58 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Minchan Kim <minchan@...nel.org>,
        zhouxianrong <zhouxianrong@...wei.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        sergey.senozhatsky@...il.com, ngupta@...are.org,
        Mi.Sophia.Wang@...wei.com, zhouxiyu@...wei.com,
        weidu.du@...wei.com, zhangshiming5@...wei.com,
        won.ho.park@...wei.com
Subject: Re: [PATCH] mm: extend zero pages to same element pages for zram

On (01/24/17 18:48), Matthew Wilcox wrote:
> On Wed, Jan 25, 2017 at 10:32:44AM +0900, Sergey Senozhatsky wrote:
> > Hello,
> > 
> > On (01/25/17 10:29), Minchan Kim wrote:
> > [..]
> > > > the result as listed below:
> > > > 
> > > > zero    pattern_char   pattern_short   pattern_int   pattern_long   total      (unit)
> > > > 162989  14454          3534            23516         2769           3294399    (page)
> > > > 
> > >
> > > so, int covers 93%. As considering non-zero dedup hit ratio is low, I think *int* is
> > > enough if memset is really fast. So, I'd like to go with 'int' if Sergey doesn't mind.
> > 
> > yep, 4 byte pattern matching and memset() sounds like a good plan to me
> 
> what?  memset ONLY HANDLES BYTES.
> 
> I pointed this out earlier, but you don't seem to be listening.  Let me
> try it again.
> 
> MEMSET ONLY HANDLES BYTES.

dammit... how did that happen...


Matthew, you are absolute right. and, yes, I missed out your previous
mail, indeed. sorry. and thanks for "re-pointing" that out.


Minchan, zhouxianrong, I was completely wrong. we can't
do memset(). d'oh, I did not know it truncates 4 bytes to
one byte only (doesn't make too much sense to me).

my apologies.

	-ss