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

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Message-ID: <93bafc81-b690-dff1-73fc-924d9fd897aa@huawei.com>
Date:   Mon, 23 Jan 2017 14:17:23 +0800
From:   zhouxianrong <zhouxianrong@...wei.com>
To:     Joonsoo Kim <iamjoonsoo.kim@....com>,
        Minchan Kim <minchan@...nel.org>
CC:     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

i am not sure as well about reverse hurting cache.

On 2017/1/23 14:13, Joonsoo Kim wrote:
> 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.
>
>
> .
>