From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752877AbZEVIQX (ORCPT ); Fri, 22 May 2009 04:16:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751796AbZEVIQL (ORCPT ); Fri, 22 May 2009 04:16:11 -0400 Received: from viefep20-int.chello.at ([62.179.121.40]:61993 "EHLO viefep20-int.chello.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752760AbZEVIQJ (ORCPT ); Fri, 22 May 2009 04:16:09 -0400 X-SourceIP: 213.93.53.227 Subject: Re: [PATCH 2/2] perf_counter: optimize context switch between identical inherited contexts From: Peter Zijlstra To: Paul Mackerras Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Corey Ashford , Thomas Gleixner In-Reply-To: <18966.10666.517218.332164@cargo.ozlabs.ibm.com> References: <18966.10075.781053.231153@cargo.ozlabs.ibm.com> <18966.10666.517218.332164@cargo.ozlabs.ibm.com> Content-Type: text/plain Date: Fri, 22 May 2009 10:16:09 +0200 Message-Id: <1242980169.26820.617.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2009-05-22 at 14:27 +1000, Paul Mackerras wrote: > Since we don't have individual fds for the counters in a cloned > context, the only thing that can make two clones of a given parent > different after they have been cloned is enabling or disabling all > counters with prctl. To account for this, we keep a count of the > number of enabled counters in each context. Two contexts must have > the same number of enabled counters to be considered equivalent. Curious point that.. so prctl() can disable counters it doesn't own. Shouldn't we instead fix that?