linux-kernel - Re: [PATCH 0/2] execve scalability issues, part 1

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Date:   Tue, 22 Aug 2023 11:51:54 +0200
From:   Jan Kara <jack@...e.cz>
To:     Mateusz Guzik <mjguzik@...il.com>
Cc:     Dennis Zhou <dennis@...nel.org>, linux-kernel@...r.kernel.org,
        tj@...nel.org, cl@...ux.com, akpm@...ux-foundation.org,
        shakeelb@...gle.com, linux-mm@...ck.org, jack@...e.cz
Subject: Re: [PATCH 0/2] execve scalability issues, part 1

On Tue 22-08-23 00:29:49, Mateusz Guzik wrote:
> On 8/21/23, Mateusz Guzik <mjguzik@...il.com> wrote:
> > True Fix(tm) is a longer story.
> >
> > Maybe let's sort out this patchset first, whichever way. :)
> >
> 
> So I found the discussion around the original patch with a perf
> regression report.
> 
> https://lore.kernel.org/linux-mm/20230608111408.s2minsenlcjow7q3@quack3/
> 
> The reporter suggests dodging the problem by only allocating per-cpu
> counters when the process is going multithreaded. Given that there is
> still plenty of forever single-threaded procs out there I think that's
> does sound like a great plan regardless of what happens with this
> patchset.
> 
> Almost all access is already done using dedicated routines, so this
> should be an afternoon churn to sort out, unless I missed a
> showstopper. (maybe there is no good place to stuff a flag/whatever
> other indicator about the state of counters?)
> 
> That said I'll look into it some time this or next week.

Good, just let me know how it went, I also wanted to start looking into
this to come up with some concrete patches :). What I had in mind was that
we could use 'counters == NULL' as an indication that the counter is still
in 'single counter mode'.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR