linux-kernel - Re: [Problem] Cache line starvation

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Date:   Tue, 2 Oct 2018 08:31:59 +0200
From:   Daniel Wagner <wagi@...om.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     linux-kernel@...r.kernel.org,
        Daniel Wagner <daniel.wagner@...mens.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will.deacon@....com>, x86@...nel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Boqun Feng <boqun.feng@...il.com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [Problem] Cache line starvation

On Fri, Sep 21, 2018 at 02:02:26PM +0200, Sebastian Andrzej Siewior wrote:
> This matches Daniel Wagner's observations which he described in [0] on
> v4.4-RT.

Peter Z recommended to drop to ticket spinlocks instead trying to port
back all the qspinlock changes to v4.4-rt.

With ticket spinlocks, 'stress-ng --ptrace 4' run for 50 hours without
a problem (before it was seconds) and my normal workload for -rt testing
for 60 hours without a problem (before it broke within 24h).

The cyclictest max values went slightly down from 32us to 30us but
that might just be coincidence.

Thanks,
Daniel