From: David Miller <davem@davemloft.net>
To: heiko.carstens@de.ibm.com
Cc: folkert@vanheusden.com, mingo@elte.hu, peterz@infradead.org,
schwidefsky@de.ibm.com, borntraeger@de.ibm.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mutex: have non-spinning mutexes on s390 by default
Date: Mon, 20 Apr 2009 05:04:03 -0700 (PDT) [thread overview]
Message-ID: <20090420.050403.56531925.davem@davemloft.net> (raw)
In-Reply-To: <20090420140103.27d92d7d@osiris.boeblingen.de.ibm.com>
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Mon, 20 Apr 2009 14:01:03 +0200
> On Fri, 17 Apr 2009 23:42:12 +0200
> Folkert van Heusden <folkert@vanheusden.com> wrote:
>
>> > The adaptive spinning mutexes will not always do what one would expect on
>> > virtualized architectures like s390. Especially the cpu_relax() loop in
>> > mutex_spin_on_owner might hurt if the mutex holding cpu has been scheduled
>> > away by the hypervisor.
>> > We would end up in a cpu_relax() loop when there is no chance that the
>> > state of the mutex changes until the target cpu has been scheduled again by
>> > the hypervisor.
>> > For that reason we should change the default behaviour to no-spin on s390.
>>
>> Hmmm. Wouldn't this be a change that applies to ibm system p as wel?
>> E.g. with linux in an lpar.
>
> This applies to every kernel that runs under a hypervisor.
I wouldn't say "every" because this change is definitely not
appropriate on sparc64 hypervisor based systems.
prev parent reply other threads:[~2009-04-20 12:04 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-09 15:47 [PATCH] mutex: have non-spinning mutexes on s390 by default Heiko Carstens
2009-04-09 15:54 ` Peter Zijlstra
2009-04-09 16:14 ` Heiko Carstens
2009-04-09 16:48 ` Heiko Carstens
2009-04-09 16:53 ` Peter Zijlstra
2009-04-09 17:38 ` Peter Zijlstra
2009-04-09 17:50 ` Jeremy Fitzhardinge
2009-04-09 18:34 ` Peter Zijlstra
2009-04-09 18:12 ` [tip:core/urgent] " Heiko Carstens
2009-04-17 21:42 ` [PATCH] " Folkert van Heusden
2009-04-20 12:01 ` Heiko Carstens
2009-04-20 12:04 ` David Miller [this message]
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