From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [PATCH RFC V6 0/11] Paravirtualized ticketlocks Date: Sat, 31 Mar 2012 00:18:36 +0200 Message-ID: <20120330221836.GN17822@one.firstfloor.org> References: <20120321102041.473.61069.sendpatchset@codeblue.in.ibm.com> <4F7616F5.4070000@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Thomas Gleixner Cc: the arch/x86 maintainers , KVM , Konrad Rzeszutek Wilk , Peter Zijlstra , Stefano Stabellini , Raghavendra K T , LKML , Andi Kleen , Srivatsa Vaddagiri , Avi Kivity , Jeremy Fitzhardinge , "H. Peter Anvin" , Attilio Rao , Ingo Molnar , Virtualization , Linus Torvalds , Xen Devel , Stephan Diestelhorst List-Id: xen-devel@lists.xenproject.org > So if a guest exits due to an external event it's easy to inspect the > state of that guest and avoid to schedule away when it was interrupted > in a spinlock held section. That guest/host shared state needs to be On a large system under high contention sleeping can perform surprisingly well. pthread mutexes have a tendency to beat kernel spinlocks there. So avoiding sleeping locks completely (that is what pv locks are essentially) is not necessarily that good. Your proposal is probably only a good idea on low contention and relatively small systems. -Andi -- ak@linux.intel.com -- Speaking for myself only.