linux-kernel - Re: [mm] f35b5d7d67: will-it-scale.per_process

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Date:   Fri, 2 Dec 2022 07:43:17 +0100
From:   Thorsten Leemhuis <regressions@...mhuis.info>
To:     "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [mm] f35b5d7d67: will-it-scale.per_process_ops -95.5% regression
 #forregzbot

On 29.11.22 09:59, Thorsten Leemhuis wrote:
> [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.]
> 
> 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

#regzbot fix: revert "mm: align larger anonymous mappings on THP boundaries"

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.