From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: Preemptable Ticket Spinlock Date: Mon, 22 Apr 2013 22:44:35 +0200 Message-ID: <1366663475.8337.10.camel@laptop> References: <51745650.9050204@redhat.com> <1366631460.4443.3.camel@laptop> <51753289.70406@redhat.com> <1366660147.6454.6.camel@laptop> <517595FA.800@redhat.com> <1366661294.6454.18.camel@laptop> <51759E43.2080003@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Jiannan Ouyang , LKML , Raghavendra K T , Avi Kivity , Gleb Natapov , Ingo Molnar , Marcelo Tosatti , Srikar , "H. Peter Anvin" , "Nikunj A. Dadhania" , KVM , Thomas Gleixner , Chegu Vinod , "Andrew M. Theurer" , Srivatsa Vaddagiri , Andrew Jones , Karen Noel To: Rik van Riel Return-path: Received: from merlin.infradead.org ([205.233.59.134]:45598 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754852Ab3DVUoi (ORCPT ); Mon, 22 Apr 2013 16:44:38 -0400 Received: from dhcp-089-099-019-018.chello.nl ([89.99.19.18] helo=dyad.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.80.1 #2 (Red Hat Linux)) id 1UUNbK-0001Ys-9p for kvm@vger.kernel.org; Mon, 22 Apr 2013 20:44:38 +0000 In-Reply-To: <51759E43.2080003@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Mon, 2013-04-22 at 16:32 -0400, Rik van Riel wrote: > > IIRC one of the reasons was that the performance improvement wasn't > as obvious. Rescheduling VCPUs takes a fair amount of time, quite > probably more than the typical hold time of a spinlock. IIRC it would spin for a while before blocking.. /me goes re-read some of that thread... Ah, its because PLE is curing most of it.. !PLE it had huge gains but apparently nobody cares about !PLE hardware anymore :-)