Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932543AbaJVJMz (ORCPT ); Wed, 22 Oct 2014 05:12:55 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:33151 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932254AbaJVJMx (ORCPT ); Wed, 22 Oct 2014 05:12:53 -0400 Date: Wed, 22 Oct 2014 11:12:39 +0200 From: Peter Zijlstra To: Stephane Eranian Cc: LKML , "mingo@elte.hu" , "ak@linux.intel.com" , Jiri Olsa , "Liang, Kan" , Borislav Petkov , Maria Dimakopoulou Subject: Re: [PATCH v2 0/12] perf/x86: implement HT leak workaround for SNB/IVB/HSW Message-ID: <20141022091239.GG12706@worktop.programming.kicks-ass.net> References: <1412872486-2930-1-git-send-email-eranian@google.com> <20141021112501.GY23531@worktop.programming.kicks-ass.net> <20141021130320.GE12706@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 21, 2014 at 03:08:32PM +0200, Stephane Eranian wrote: > On Tue, Oct 21, 2014 at 3:03 PM, Peter Zijlstra wrote: > > On Tue, Oct 21, 2014 at 02:28:06PM +0200, Stephane Eranian wrote: > >> Peter, > >> > >> On Tue, Oct 21, 2014 at 1:25 PM, Peter Zijlstra wrote: > >> > > >> > > >> > lkml.kernel.org/r/CABPqkBRbst4sgpgE5O_VXt-CSC0VD=aP2KWA0e3Uy64tw7df3A@mail.gmail.com > >> > > >> > I missed that 3 lines if they were in here. > >> > > >> I did not put them in there because there is another problem. > >> If you partition the generic counters 2 and 2, then some CPUs will not > >> be able to measure some events. > >> Unfortunately, there is no way to partition the 4 counters such that > >> all the events can be measured by > >> each CPU. Some events or precise sampling requires counter 2 for > >> instance (like prec_dist). > >> That's why I did not put this fix in. > > > > Ah, I wasn't thinking about a hard partition, just a limit on the number > > of exclusive counters any one CPU can claim such as to not starve. Or is > > that what you were talking about? I feel not being able to starve > > another CPU is more important than a better utilization bound for > > counter scheduling. > > So you're saying, just limit number of used counters to 2 regardless > of which one they are. used as in marked exclusive and forced empty on the other side. > So sometimes, this will avoid the problem aforementioned and sometimes > not. We can try that. How will this sometimes not avoid the starvation issue? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/