From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754723AbZBFEeg (ORCPT ); Thu, 5 Feb 2009 23:34:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751341AbZBFEe1 (ORCPT ); Thu, 5 Feb 2009 23:34:27 -0500 Received: from ozlabs.org ([203.10.76.45]:53151 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751259AbZBFEe0 (ORCPT ); Thu, 5 Feb 2009 23:34:26 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <18827.48582.613391.869829@cargo.ozlabs.ibm.com> Date: Fri, 6 Feb 2009 15:34:14 +1100 From: Paul Mackerras To: Ingo Molnar Cc: "Zhang, Yanmin" , linux-kernel@vger.kernel.org Subject: Re: [PATCH] perf_counter: Prevent oopses from per-cpu software counters In-Reply-To: <20090205142229.GB28443@elte.hu> References: <18826.28805.120988.303819@drongo.ozlabs.ibm.com> <20090205142229.GB28443@elte.hu> X-Mailer: VM 8.0.9 under Emacs 22.2.1 (i486-pc-linux-gnu) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ingo Molnar writes: > So how about fixing these sw counts to properly work as percpu counters too? OK, so for page faults it looks like I want to look at get_cpu_var(vm_event_states).event[PGFAULT] to get the per-cpu page fault count, as long as CONFIG_VM_EVENT_COUNTERS is set. It looks like the scheduler doesn't keep per-cpu counts of context switches or task migrations, or if it does I couldn't find them. We could do stuff in perf_counter_task_sched_in/out to implement per-cpu context switch and migration counters by adding up the delta values for each task that gets scheduled onto the cpu. Or we could add explicit per-cpu counters for these things in the scheduler. What do you think? Paul.