linux-kernel - Re: [PATCHv2 0/3] Allow ZRAM to use any zpool-compatible backend

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Message-ID: <CAMJBoFPrPuPpcfNCKGF0EkSZ+0R7Un6HuoQhBPsznjVTUkVBSQ@mail.gmail.com>
Date:   Fri, 20 Dec 2019 07:04:05 +0100
From:   Vitaly Wool <vitalywool@...il.com>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Linux-MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Streetman <ddstreet@...e.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Shakeel Butt <shakeelb@...gle.com>,
        Henry Burns <henrywolfeburns@...il.com>,
        "Theodore Ts'o" <tytso@...nk.org>
Subject: Re: [PATCHv2 0/3] Allow ZRAM to use any zpool-compatible backend

On Fri, Dec 20, 2019 at 4:14 AM Minchan Kim <minchan@...nel.org> wrote:

<snip>
> Look https://lkml.org/lkml/2019/10/29/1169
>
> z3fold read is 15% faster *only* when when compression ratio is bad below 50%
> since zsmalloc involves copy operation if the object is located in the
> boundary of discrete pages. It's never popular workload.
> Even, once write is involved(write-only, mixed read-write), z3fold is always
> slow. Think about that swap-in could cause swap out in the field because devices
> are usually under memory pressure. Also, look at the memory usage.
> zsmalloc saves bigger memory for all of compression ratios.

Yes I remember that. Since your measurements were done on "an x86" without
providing any detail on the actual platform used, they are as good as none.

~Vitaly