From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935400AbYEBR2U (ORCPT ); Fri, 2 May 2008 13:28:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S935136AbYEBR1g (ORCPT ); Fri, 2 May 2008 13:27:36 -0400 Received: from x346.tv-sign.ru ([89.108.83.215]:53837 "EHLO mail.screens.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935048AbYEBR1f (ORCPT ); Fri, 2 May 2008 13:27:35 -0400 Date: Fri, 2 May 2008 21:28:03 +0400 From: Oleg Nesterov To: Bj?rn Steinbrink Cc: Petr Tesarik , Thomas Gleixner , linux-kernel@vger.kernel.org, Roland McGrath , Frank Mayhar Subject: Re: CPU POSIX timers livelock Message-ID: <20080502172803.GA1541@tv-sign.ru> References: <1209740741.15210.49.camel@elijah.suse.cz> <20080502152126.GA3130@atjola.homenet> <1209744785.15210.52.camel@elijah.suse.cz> <20080502164334.GA3585@atjola.homenet> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080502164334.GA3585@atjola.homenet> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/02, Bj?rn Steinbrink wrote: > > Hm, I have some message in that thread from April they don't seem to be > on lkml.org nor in the bugzilla though. Oh well, I can send you an mbox > of that thread in a private mail, just let me know if you want that. Me too please ;) Please note there is a related problem if we have a single thread but a lot of timers attached to this thread. If the signal is ignored, each timer should be re-armed, this all can consume >= 1/HZ CPU time. We have "maxfire = 20" in check_thread_timers/check_process_timers to prevent this, but it is just a workaround. And it is a bit silly to just waste the CPU if the signal is ignored, arm_timer() is heavy and doesn't scale well. However, I have already forgot this code, perhaps I missed something, and at least maxfire does help. Oleg.