linux-kernel - Re:Re: [PATCH 1/2] f2fs: add sysfs nodes to get discard information

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Date:   Mon, 16 Aug 2021 14:13:40 +0800 (GMT+08:00)
From:   李扬韬 <frank.li@...o.com>
To:     Chao Yu <chao@...nel.org>
Cc:     jaegeuk@...nel.org, linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re:Re: [PATCH 1/2] f2fs: add sysfs nodes to get discard information

>>>> I've added new sysfs nodes to show discard stat since mount, which
>>>> will help us analyze whether the performance problem is related to
>>>> discard.
>>>>
>>>> issued_discard  - Shows the number of issued discard
>>>> queued_discard  - Shows the number of cached discard cmd count
>>>> discard_cmd_cnt - Shows the number of cached discard cmd count
>>>> undiscard_blks  - Shows the number of undiscard blocks
>>>
>>> We have exported them in debugfs, can you use that?
>>>
>>> Thanks,
>> 
>> But now Android is forbidden to open debugfs, and in fact we have not
>> opened this configuration for a long time.
>
>Weren't them be used for debug purpose? can you please explain more about
>your use case?

During long-term aging test or normal use, sometimes there will be performance
degradation problems. It may be caused by storage, or it may be caused by the
filesystem. For example, the filesystem accumulates a large number of undiscard
 blocks. Although there is some remaining space, the androidbench test will
show performance degradation. Therefore, it is necessary to export information
related to discard so that we can confirm this situation.

Thx,