Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754252AbaJWI6D (ORCPT ); Thu, 23 Oct 2014 04:58:03 -0400 Received: from mail-oi0-f42.google.com ([209.85.218.42]:38593 "EHLO mail-oi0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753892AbaJWI56 (ORCPT ); Thu, 23 Oct 2014 04:57:58 -0400 MIME-Version: 1.0 In-Reply-To: <20141023085310.GN21513@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> <20141022091239.GG12706@worktop.programming.kicks-ass.net> <20141023085310.GN21513@worktop.programming.kicks-ass.net> Date: Thu, 23 Oct 2014 10:57:57 +0200 Message-ID: Subject: Re: [PATCH v2 0/12] perf/x86: implement HT leak workaround for SNB/IVB/HSW From: Stephane Eranian To: Peter Zijlstra Cc: LKML , "mingo@elte.hu" , "ak@linux.intel.com" , Jiri Olsa , "Liang, Kan" , Borislav Petkov , Maria Dimakopoulou Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 23, 2014 at 10:53 AM, Peter Zijlstra wrote: > On Wed, Oct 22, 2014 at 11:04:31PM +0200, Stephane Eranian wrote: >> Here is a simple case: >> Limiting each HT to only 2 counters, can be any, 2 out of 4 possible. >> >> HT0: you measure a MEM* in ctr2, it is started first, and it keeps running >> HT1: you measure PREC_DIST with PEBS (it requires ctr2) >> >> HT0 is measuring a corrupting event on ctr2, this prevents ctr2 on HT1 >> from being used. >> HT1 is starved, it cannot measure PREC_DIST >> >> Yes you have a quota of 2 out of 4 counters. >> >> The quota dynamic or static can help mitigate the starvation. The only >> way to eliminate >> it is to force multiplexing even though you are using fewer counters >> than actually avail. > > Ah yes, the very narrowly constrained events. Those suck indeed. And I > imagine rotation might not even help here -- rotation doesn't guarantee > SMT1 will try and schedule before SMT0, in fact there are setups > (staggered tick) where its almost guaranteed not to. > > Still I suppose for 'normal' event its a much better state, SMT1 can > always schedule some events. Yes, I agree with you. The soft partition helps. I will add that in V3. Thanks. -- 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/