linux-kernel - Re: [PATCH 2/3] selftests/zram01.sh: Fix compression ratio calculation

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Date:   Wed, 26 Jan 2022 06:08:42 +0000
From:   "xuyang2018.jy@...itsu.com" <xuyang2018.jy@...itsu.com>
To:     Shuah Khan <skhan@...uxfoundation.org>
CC:     "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "shuah@...nel.org" <shuah@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "naresh.kamboju@...aro.org" <naresh.kamboju@...aro.org>,
        "aleksei.kodanev@...l-sw.com" <aleksei.kodanev@...l-sw.com>
Subject: Re: [PATCH 2/3] selftests/zram01.sh: Fix compression ratio
 calculation

on 2022/1/26 4:37, Shuah Khan wrote:
> On 12/15/21 2:56 AM, Yang Xu wrote:
>> zram01 uses `free -m` to measure zram memory usage. The results are
>> nonsense
>> because they are polluted by all running processes on the system.
>>
>
> Are the results inaccurate or does /sys/block/zram<id>/mm_stat is a quick
> way to get the information?
The "free -m" result is inaccurate because it caculted global systemd 
free memory instead of process that used zram device.

We should use mm_stat as Documentation/admin-guide/blockdev/zram.rst wrote:

File /sys/block/zram<id>/mm_stat

The mm_stat file represents the device's mm statistics. It consists of a 
single
line of text and contains the following stats separated by whitespace:

  ================ 
=============================================================
  orig_data_size   uncompressed size of data stored in this disk.
                   Unit: bytes
  compr_data_size  compressed size of data stored in this disk
  mem_used_total   the amount of memory allocated for this disk. This
                   includes allocator fragmentation and metadata
>
> In any case, this patch and all 3 patches in this series have:
>
> WARNING: Possible unwrapped commit description (prefer a maximum 75
> chars per line)
>
> Please run checkpatch.pl and clean these up.
Ok, Will do it in v2.

Best Regards
Yang Xu
>
> thanks,
> -- Shuah