From: "Linux regression tracking (Thorsten Leemhuis)" <regressions@leemhuis.info>
To: Roman Gushchin <roman.gushchin@linux.dev>,
Linux regressions mailing list <regressions@lists.linux.dev>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Shakeel Butt <shakeelb@google.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Muchun Song <muchun.song@linux.dev>,
Andrew Morton <akpm@linux-foundation.org>,
Waiman Long <longman@redhat.com>,
Sven Luther <Sven.Luther@windriver.com>
Subject: Re: [PATCH RFC] ipc/mqueue: introduce msg cache
Date: Fri, 24 Feb 2023 11:47:14 +0100 [thread overview]
Message-ID: <07e61f29-5a0e-be38-ad24-01aefdf970bd@leemhuis.info> (raw)
In-Reply-To: <Y+/GxJcNykVQxcG+@P9FQF9L96D.corp.robot.car>
[TLDR: This mail in primarily relevant for Linux kernel regression
tracking. See link in footer if these mails annoy you.]
On 17.02.23 19:26, Roman Gushchin wrote:
> On Thu, Feb 16, 2023 at 01:29:59PM +0100, Linux regression tracking (Thorsten Leemhuis) wrote:
>>
>> On 20.12.22 19:48, Roman Gushchin wrote:
>>> Sven Luther reported a regression in the posix message queues
>>> performance caused by switching to the per-object tracking of
>>> slab objects introduced by patch series ending with the
>>> commit 10befea91b61 ("mm: memcg/slab: use a single set of kmem_caches for all
>>> allocations").
>>
>> Quick inquiry: what happened to below patch? It was supposed to fix a
>> performance regression reported here:
>
> I wouldn't call it simple a regression,
Well, performance regressions are regressions, too. That being said:
> things a bit more complicated:
> it was a switch to a different approach with different trade-offs,
> which IMO make more sense for the majority of real-world workloads.
> In two words: individual kernel memory allocations became somewhat slower
> (but still fast), but we've saved 40%+ of slab memory on typical systems
> and reduced the memory fragmentation.
>
> The regression reported by Sven and my "fix" are related to one very specific
> case: posix message queues. To my knowledge they are not widely used for
> anything that performance-sensitive, so it's quite a niche use case.
> My "fix" was also hand-crafted for the benchmark provided by Sven, so it might
> not work for a more generic case. And I don't think it can be easily generalized
> without adding cpu or memory overhead.
>
> On the other hand I'm working on improving the speed of kernel memory allocations
> in general (I posted early versions some weeks ago). Hopefully it will mitigate
> the problem for Sven as well, so we won't need these message queue-specific
> hacks.
Thx for the explanation. Sven didn't complain and it seems no one else
run into this, so I think we can live with that state of affairs.
#regzbot inconclusive: not fixed, but cause by a trade-off and a likely
corner-case anyway; more optimizations planned to improve things
#regzbot ignore-activity
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.
prev parent reply other threads:[~2023-02-24 10:47 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-20 18:48 [PATCH RFC] ipc/mqueue: introduce msg cache Roman Gushchin
2022-12-20 19:53 ` Shakeel Butt
2022-12-20 20:59 ` Roman Gushchin
2022-12-20 23:28 ` Shakeel Butt
2022-12-20 23:56 ` Roman Gushchin
2022-12-21 9:29 ` Thorsten Leemhuis
2022-12-22 11:52 ` Brian Foster
2022-12-22 16:37 ` Roman Gushchin
2022-12-22 17:54 ` Brian Foster
2023-02-16 12:29 ` Linux regression tracking (Thorsten Leemhuis)
2023-02-17 18:26 ` Roman Gushchin
2023-02-24 10:47 ` Linux regression tracking (Thorsten Leemhuis) [this message]
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