linux-kernel - Re: [REGRESSION]: mmap performance regression starting with k-6.1

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Message-ID: <2541055a-48c9-4680-ad9b-5a3c41995a1d@leemhuis.info>
Date:   Fri, 24 Nov 2023 06:08:24 +0100
From:   "Linux regression tracking #update (Thorsten Leemhuis)" 
        <regressions@...mhuis.info>
To:     "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Bagas Sanjaya <bagasdotme@...il.com>,
        Chun Ng <chunn@...dia.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Regressions <regressions@...ts.linux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Ankita Garg <ankitag@...dia.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>
Subject: Re: [REGRESSION]: mmap performance regression starting with k-6.1

[TLDR: This mail in primarily relevant for Linux kernel regression
tracking. See link in footer if these mails annoy you.]

On 23.11.23 15:34, Liam R. Howlett wrote:
> * Bagas Sanjaya <bagasdotme@...il.com> [231123 00:07]:
>> On Wed, Nov 22, 2023 at 08:03:19PM +0000, Chun Ng wrote:
>>>
>>> Recently I observed there is performance regression on system call mmap(..). I tried both vanilla kernels and Raspberry Pi kernels on a Raspberry Pi 4 box and the results are pretty consistent among them.
>>>
>>> Bisection showed that the regression starts from k-6.1, and the latest vanilla k-6.7 is still showing the same regression.
> 
> This is almost certainly the maple tree.  The tree is slower on writes
> than the rbtree and so if the benchmark mmaps/munmaps in a tight loop
> you will see this slow down. [...]
>
>> Anyway, I'm adding this regression to regzbot:
>> #regzbot ^introduced: v6.0..v6.1

Liam, many thx for your reply. I known that you are still working on
optimizing things in this area again, so I don't think this is worth
tracking this as a regression: that doesn't buy us much afaics. And it
might not be a regression at all anyway (not totally sure, didn't look
into the details due to the former aspect; sounded a bit like the
problem only can be seen in a microbenchmark; whatever).

#regzbot resolve: not worth tracking

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
--
Everything you wanna know about Linux kernel regression tracking:
https://linux-regtracking.leemhuis.info/about/#tldr
If I did something stupid, please tell me, as explained on that page.