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Date: Mon, 20 Apr 2009 05:04:03 -0700 (PDT) From: David Miller <davem@...emloft.net> To: heiko.carstens@...ibm.com Cc: folkert@...heusden.com, mingo@...e.hu, peterz@...radead.org, schwidefsky@...ibm.com, borntraeger@...ibm.com, linux-kernel@...r.kernel.org Subject: Re: [PATCH] mutex: have non-spinning mutexes on s390 by default From: Heiko Carstens <heiko.carstens@...ibm.com> Date: Mon, 20 Apr 2009 14:01:03 +0200 > On Fri, 17 Apr 2009 23:42:12 +0200 > Folkert van Heusden <folkert@...heusden.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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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