Re: [mm] f35b5d7d67: will-it-scale.per_process_ops -95.5% regression #forregzbot

From: Thorsten Leemhuis <regressions@leemhuis.info>
To: "regressions@lists.linux.dev" <regressions@lists.linux.dev>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [mm] f35b5d7d67: will-it-scale.per_process_ops -95.5% regression #forregzbot
Date: Tue, 29 Nov 2022 09:59:39 +0100	[thread overview]
Message-ID: <84964891-5a39-adb2-3093-54b716ca94ae@leemhuis.info> (raw)
In-Reply-To: <Y1DNQaoPWxE+rGce@dev-arch.thelio-3990X>

[Note: this mail is primarily send for documentation purposes and/or for
regzbot, my Linux kernel regression tracking bot. That's why I removed
most or all folks from the list of recipients, but left any that looked
like a mailing lists. These mails usually contain '#forregzbot' in the
subject, to make them easy to spot and filter out.]

[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.]

Hi, this is your Linux kernel regression tracker.

On 20.10.22 06:23, Nathan Chancellor wrote:
> [...]
> For what it's worth, I just bisected a massive and visible performance
> regression on my Threadripper 3990X workstation to commit f35b5d7d676e
> ("mm: align larger anonymous mappings on THP boundaries"), which seems
> directly related to this report/analysis. I initially noticed this
> because my full set of kernel builds against mainline went from 2 hours
> and 20 minutes or so to over 3 hours. Zeroing in on x86_64 allmodconfig,
> which I used for the bisect:

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 f35b5d7d676e59e4
#regzbot title performance: mm: building Linux with clang takes a lot
longer (~27 %)
#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; above webpage 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.