linux-kernel - Re: [patch 00/11] rseq: Optimize exit to user space

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Message-ID: <87a53wxtx5.ffs@tglx>
Date: Mon, 18 Aug 2025 22:21:26 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Michael Jeanson <mjeanson@...icios.com>, Jens Axboe <axboe@...nel.dk>,
 LKML <linux-kernel@...r.kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Peter Zijlstra
 <peterz@...radead.org>, "Paul E. McKenney" <paulmck@...nel.org>, Boqun
 Feng <boqun.feng@...il.com>, Wei Liu <wei.liu@...nel.org>
Subject: Re: [patch 00/11] rseq: Optimize exit to user space

On Mon, Aug 18 2025 at 13:38, Michael Jeanson wrote:

> On 2025-08-17 17:23, Thomas Gleixner wrote:
>> Michael, can you please run your librseq tests against that too? They
>> have the same segfault problem as the kernel and they lack a run script,
>> so I couldn't be bothered to test against them. See commit 2bff3a0e5998
>> in that branch. I'll send out a patch with a proper change log later.
>
> I ran the librseq test suite on the new branch on a Debian Trixie amd64 
> system and it succeeds, here are the rseq stats before and after.

Thanks!

> Before:
>
> exit:             746809
> signal:                3
> slowp:                99
> ids:                1053
> cs:                    0
> clear:                 0
> fixup:                 0
>
> After:
>
> exit:          229294046
> signal:               11
> slowp:              4570
> ids:              615950
> cs:              2493682
> clear:            194637
> fixup:           2299044

That looks about right. Can you reset the branch to

     commit 85b61b265635 ("rseq: Expose stats")

which is just adding primitive stats on top of the current mainline
code, and provide numbers for that too?

That gives you 'notify: , cpuid:, fixup:' numbers, which are not 1:1
mappable to the final ones, but that should give some interesting
insight.

> If you want to run the librseq tests on your system, just do the regular 
> autotools dance and then run 'make check'.

Might be useful to put such instructions into README.md, no?

Thanks,

        tglx