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

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Message-ID: <alpine.DEB.2.21.1809211453170.14736@nanos.tec.linutronix.de>
Date:   Fri, 21 Sep 2018 14:54:32 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Daniel Wagner <daniel.wagner@...mens.com>,
        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, 21 Sep 2018, Peter Zijlstra wrote:
> On Fri, Sep 21, 2018 at 02:02:26PM +0200, Sebastian Andrzej Siewior wrote:
> > We reproducibly observe cache line starvation on a Core2Duo E6850 (2
> > cores), a i5-6400 SKL (4 cores) and on a NXP LS2044A ARM Cortex-A72 (4
> > cores).
> > 
> > The problem can be triggered with a v4.9-RT kernel by starting
> 
> > Daniel reported that disabling ticket locks on 4.4 makes the problem go
> > away, but he hasn't run a long time test yet and as we saw with 4.14 it can
> > take quite a while.
> 
> On 4.4 and 4.9 ARM64 still uses ticket locks. So I'm very interested to
> know if the ticket locks on x86 really fix or just make it harder.

We can run 4.4. with ticket locks over the weekend.

Thanks,

	tglx