From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752331AbaGKNXP (ORCPT ); Fri, 11 Jul 2014 09:23:15 -0400 Received: from casper.infradead.org ([85.118.1.10]:41009 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751943AbaGKNXO (ORCPT ); Fri, 11 Jul 2014 09:23:14 -0400 Date: Fri, 11 Jul 2014 15:23:09 +0200 From: Peter Zijlstra To: Jiri Olsa Cc: linux-kernel@vger.kernel.org, Jiri Olsa , Alexander Yarygin , Arnaldo Carvalho de Melo , Corey Ashford , Frederic Weisbecker , Ingo Molnar , Paul Mackerras Subject: Re: [PATCH 2/5] perf: Destroy event's children on task exit Message-ID: <20140711132309.GH20603@laptop.programming.kicks-ass.net> References: <1405079782-8139-1-git-send-email-jolsa@kernel.org> <1405079782-8139-3-git-send-email-jolsa@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1405079782-8139-3-git-send-email-jolsa@kernel.org> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 11, 2014 at 01:56:19PM +0200, Jiri Olsa wrote: > From: Jiri Olsa > > When task exits we close: > 1) all events that are installed in task > 2) all events owned by task (via file descriptor) > > But we don't close children events of 2) events. Those children > events stay until the child task exits and are useless with the > parent being gone, because we have no way to get to values any > more. > > Plus if the event stays installed in task even with the owner task > gone, it runs the perf callback any time the task forks, for no > real reason. > > Closing all children events events when the owner task of the > parent event is closed. So I _think_ the reason we didn't do this is because this is potentially very expensive and keeping them around isn't too much bother, they'll die eventually. But I can't really remember. Ingo any recollections / opinions?