linux-kernel - Re: user-space concurrent pipe buffer scheduler interactions

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Message-ID: <CAHk-=wiOqTAX7nwQqHJ2Ti3dbxM-HrUJq3FD_Gjua5qW=QAoTg@mail.gmail.com>
Date: Wed, 3 Apr 2024 13:57:11 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Michael Clark <michael@...aparadigm.com>
Cc: Jens Axboe <axboe@...nel.dk>, Ingo Molnar <mingo@...hat.com>, 
	Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: user-space concurrent pipe buffer scheduler interactions

On Wed, 3 Apr 2024 at 13:52, Michael Clark <michael@...aparadigm.com> wrote:
>
> On 4/4/24 05:56, Linus Torvalds wrote:
> > On Tue, 2 Apr 2024 at 13:54, Michael Clark <michael@...aparadigm.com> wrote:
> >>
> >> I am working on a low latency cross-platform concurrent pipe buffer
> >> using C11 threads and atomics.
> >
> > You will never get good performance doing spinlocks in user space
> > unless you actually tell the scheduler about the spinlocks, and have
> > some way to actually sleep on contention.
> >
> > Which I don't see you as having.
>
> We can work on this.

It's been tried.

Nobody ever found a use-case that is sufficiently convincing, but see
the write-up at

   https://lwn.net/Articles/944895/

for a pointer to at least attempts.

               Linus