From: Thomas Gleixner <tglx@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
bigeasy@linutronix.de,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
daniel.wagner@siemens.com, Will Deacon <will.deacon@arm.com>,
x86@kernel.org, Linus Torvalds <torvalds@linux-foundation.org>,
"H. Peter Anvin" <hpa@zytor.com>,
boqun.feng@gmail.com, Paul McKenney <paulmck@linux.vnet.ibm.com>
Subject: Re: [Problem] Cache line starvation
Date: Wed, 3 Oct 2018 12:43:57 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.21.1810031242320.1435@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20181003082842.GN26858@hirez.programming.kicks-ass.net>
On Wed, 3 Oct 2018, Peter Zijlstra wrote:
> On Wed, Oct 03, 2018 at 10:07:05AM +0200, Thomas Gleixner wrote:
> > On Wed, 3 Oct 2018, Catalin Marinas wrote:
> >
> > > On Fri, 21 Sep 2018 at 13:22, Peter Zijlstra <peterz@infradead.org> 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).
>
> > Except that the ARM64 ticket locks are not preventing the starvation
> > issue. Neither do the qrlocks on ARM64 on later kernels.
>
> That A72 is ARMv8-A afaict, that doesn't have the fancy LSE bits (which
> are new in ARMv8.1) on and thus ends up using LL/SC. And LL/SC has
> similar issues as cmpxchg loops.
>
> AFAICT Cortex-A75 is the first that has LSE on (that's an ARMv8.2-A).
I know. That doesn't help though. We need a solution for the v8-A and the
magic delay loop we have right now to work around it is more that
disturbing.
Thanks,
tglx
next prev parent reply other threads:[~2018-10-03 10:44 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-21 12:02 [Problem] Cache line starvation Sebastian Andrzej Siewior
2018-09-21 12:13 ` Thomas Gleixner
2018-09-21 12:50 ` Sebastian Andrzej Siewior
2018-09-21 12:20 ` Peter Zijlstra
2018-09-21 12:54 ` Thomas Gleixner
2018-10-03 7:51 ` Catalin Marinas
2018-10-03 8:07 ` Thomas Gleixner
2018-10-03 8:28 ` Peter Zijlstra
2018-10-03 10:43 ` Thomas Gleixner [this message]
2018-10-03 8:23 ` Peter Zijlstra
2018-09-26 7:34 ` Peter Zijlstra
2018-09-26 8:04 ` Thomas Gleixner
2018-09-26 12:53 ` Will Deacon
2018-09-27 14:25 ` Kurt Kanzenbach
2018-09-27 14:41 ` Kurt Kanzenbach
2018-09-27 14:47 ` Thomas Gleixner
2018-09-28 9:05 ` Kurt Kanzenbach
2018-09-28 15:26 ` Kurt Kanzenbach
2018-09-28 19:26 ` Sebastian Andrzej Siewior
2018-09-28 19:34 ` Thomas Gleixner
2018-10-02 6:31 ` Daniel Wagner
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