linux-kernel - Re: [PATCH v3] zram: extend zero pages to same element pages

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Message-ID: <20170123061350.GE24581@js1304-P5Q-DELUXE>
Date:   Mon, 23 Jan 2017 15:13:50 +0900
From:   Joonsoo Kim <iamjoonsoo.kim@....com>
To:     Minchan Kim <minchan@...nel.org>
Cc:     zhouxianrong <zhouxianrong@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        linux-kernel@...r.kernel.org, Mi.Sophia.Wang@...wei.com,
        zhouxiyu@...wei.com, weidu.du@...wei.com, zhangshiming5@...wei.com,
        won.ho.park@...wei.com
Subject: Re: [PATCH v3] zram: extend zero pages to same element pages

On Mon, Jan 23, 2017 at 01:47:20PM +0900, Minchan Kim wrote:
> Hello,
> 
> When I look at first patch, I wanted to use increment loop but didn't
> tell to you because that small piece of code is no harmful for readbility
> to me so I want to keep author's code rather than pointing the trivial
> which is just matter of preference out.
> 
> Rather than readiblity, I suspect it might hurt performance and talked
> with Namhyung but we cannot find anything decremental loop is bad
> compared to incremental. Rather than, many articles have been said
> decrement loop is faster like zhouxianrong's mentiond although I don't
> think it makes marginal difference.
> 
> Joonsoo, why do you think incremental is faster?
> zhouxianrong, why do you think decrement loops makes cache problem?
> 
> I'm okay either way. Just want to know why you guys think about it.

Hmm... I guess that cache prefetcher works better for forward access
but I'm not sure.

Thanks.