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

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Message-ID: <YRr/2DM84TishToA@google.com>
Date:   Mon, 16 Aug 2021 17:16:24 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     李扬韬 <frank.li@...o.com>
Cc:     Chao Yu <chao@...nel.org>, linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] f2fs: add sysfs nodes to get discard information

On 08/16, 李扬韬 wrote:
> >>>> 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.

I think you can mount debugfs for that case?

> 
> Thx,
> 
>