Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966622AbaFTNo6 (ORCPT ); Fri, 20 Jun 2014 09:44:58 -0400 Received: from mail-oa0-f42.google.com ([209.85.219.42]:62611 "EHLO mail-oa0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965260AbaFTNo5 (ORCPT ); Fri, 20 Jun 2014 09:44:57 -0400 MIME-Version: 1.0 In-Reply-To: References: <1403193509-22393-1-git-send-email-eranian@google.com> <1403193509-22393-2-git-send-email-eranian@google.com> <20140619180028.GU8178@tassilo.jf.intel.com> <20140619201801.GV8178@tassilo.jf.intel.com> <20140619204041.GW8178@tassilo.jf.intel.com> Date: Fri, 20 Jun 2014 15:44:56 +0200 Message-ID: Subject: Re: [PATCH 1/2] perf/x86: update Haswell PEBS event constraints From: Stephane Eranian To: Andi Kleen Cc: LKML , Peter Zijlstra , "mingo@elte.hu" , Joe Mario , Don Zickus , Jiri Olsa , Arnaldo Carvalho de Melo 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, Jun 19, 2014 at 10:45 PM, Stephane Eranian wrote: > On Thu, Jun 19, 2014 at 10:40 PM, Andi Kleen wrote: >> On Thu, Jun 19, 2014 at 10:31:29PM +0200, Stephane Eranian wrote: >>> On Thu, Jun 19, 2014 at 10:18 PM, Andi Kleen wrote: >>> >> I don't quite understand that. >>> >> You need to know which events support PEBS. You need a table >>> > >>> > We're talking about the kernel allowing things here. >>> > Yes the user still needs to know what supports PEBS, but >>> > that doesn't concern the kernel. >>> > >>> Just need to make sure you don't return bogus information. >> >> GIGO. We only need to prevent security issues. >> >>> > You can just allow it for all, it's a nop if the event doesn't >>> > support it. And also the fields like DataLA are simply 0 when >>> > not supported. >>> > >>> >>> Let's take a example. If I do resource_stalls:pp, the kernel >>> will let it go through and clear the PMI bit on the config as >>> is required for PEBS mode. The counter will count normally >>> and never fire an interrupt, even when it overflows. It would >>> never execute the PMI handler and thus never look at the >>> PEBS content. You'd never get any samples. >> >> Yes if the user specifies a bogus raw event it will not count. >> That's fine. The important part is just that nothing ever crashes. >> > That would certainly avoid the problem of missing events in pebs table. > I had a problem with that just today. It also speed up scheduling > as well by avoid the table lookups. > I can take of writing the patch to do this, if you want. > Note that I will soon post a patch to speed up scheduling for all x86 > processors. I'll put that one in too. -- 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/