linux-ext4 - Re: Ext4: Buffered random writes performance regression with dioread

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Date:   Tue, 20 Sep 2022 10:07:07 +0200
From:   Thorsten Leemhuis <regressions@...mhuis.info>
To:     hazem ahmed mohamed <hazem.ahmed.abuelfotoh@...il.com>,
        "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
        "tytso@....edu" <tytso@....edu>,
        "adilger.kernel@...ger.ca" <adilger.kernel@...ger.ca>,
        "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     "Mohamed Abuelfotoh, Hazem" <abuehaze@...zon.com>
Subject: Re: Ext4: Buffered random writes performance regression with
 dioread_nolock enabled

On 19.09.22 17:18, hazem ahmed mohamed wrote:
> 
> I am sending this e-mail to report a performance regression that’s
> caused by commit 244adf6426(ext4: make dioread_nolock the default) , I
> am listing the performance regression symptoms below & our analysis
> for the reported regression.

FWIW, that patch went into v5.6-rc1~113^2~12

And BTW: it seems 0-day back then noticed that 244adf6426 caused a
performance regression as well, but it seems that was ignored:
https://lore.kernel.org/all/20201024120829.GK31092@shao2-debian/

Anyway, now to the main reason why I write this mail:

[TLDR: I'm adding this regression report to the list of tracked
regressions; all text from me you find below is based on a few templates
paragraphs you might have encountered already already in similar form.]

Thanks for the report. To be sure below issue doesn't fall through the
cracks unnoticed, I'm adding it to regzbot, my Linux kernel regression
tracking bot:

#regzbot ^introduced 244adf6426
#regzbot ignore-activity

This isn't a regression? This issue or a fix for it are already
discussed somewhere else? It was fixed already? You want to clarify when
the regression started to happen? Or point out I got the title or
something else totally wrong? Then just reply -- ideally with also
telling regzbot about it, as explained here:
https://linux-regtracking.leemhuis.info/tracked-regression/

Reminder for developers: When fixing the issue, add 'Link:' tags
pointing to the report (the mail this one replies to), as explained for
in the Linux kernel's documentation; the webpage mention at the end of
the last para explains why this is important for tracked regressions.

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)

P.S.: As the Linux kernel's regression tracker I deal with a lot of
reports and sometimes miss something important when writing mails like
this. If that's the case here, don't hesitate to tell me in a public
reply, it's in everyone's interest to set the public record straight.