Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753799AbXFYRHA (ORCPT ); Mon, 25 Jun 2007 13:07:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750880AbXFYRGx (ORCPT ); Mon, 25 Jun 2007 13:06:53 -0400 Received: from ms-smtp-05.nyroc.rr.com ([24.24.2.59]:64293 "EHLO ms-smtp-05.nyroc.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750841AbXFYRGw (ORCPT ); Mon, 25 Jun 2007 13:06:52 -0400 Subject: Re: [RFC PATCH 0/6] Convert all tasklets to workqueues From: Steven Rostedt To: Tilman Schmidt Cc: Ingo Molnar , LKML , Andrew Morton , Thomas Gleixner , Christoph Hellwig , john stultz , Oleg Nesterov , "Paul E. McKenney" , Dipankar Sarma , "David S. Miller" , matthew.wilcox@hp.com, kuznet@ms2.inr.ac.ru, Linus Torvalds In-Reply-To: <467FF23B.30509@imap.cc> References: <10876.1182698167@lwn.net> <467FF23B.30509@imap.cc> Content-Type: text/plain Date: Mon, 25 Jun 2007 13:06:43 -0400 Message-Id: <1182791203.5493.161.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.6.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1405 Lines: 29 On Mon, 2007-06-25 at 18:50 +0200, Tilman Schmidt wrote: > The Siemens Gigaset ISDN base driver uses tasklets in its isochronous > data paths. These will be scheduled for each completion of an isochronous > URB, or every 8 msec for each of the four isochronous pipes if both B > channels are connected. The driver uses three URBs for each pipe, always > maintaining two in flight while processing the third one. So the tasklet > has to run within 16 ms from being scheduled in order to avoid packet > loss (in the receive path) or data underrun (in the transmit path). > > Does that qualify as performance sensitive for the purpose of this > discussion? Actually, no. 16ms, even 8ms is an incredible amount of time. Unless you have a thread that is running at a higher priority than the thread that handles the work queue performing the task, you would have no problems making that deadline. If you did miss the deadline without having ridiculously high prio tasks, I would think that you would miss your deadline with tasklets as well. Unless the large latency has to do with preempt_disable, but that large of a latency would be IMHO a bug. -- Steve - 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/