Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262640AbVDPLe2 (ORCPT ); Sat, 16 Apr 2005 07:34:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262650AbVDPLe2 (ORCPT ); Sat, 16 Apr 2005 07:34:28 -0400 Received: from postel.suug.ch ([195.134.158.23]:9706 "EHLO postel.suug.ch") by vger.kernel.org with ESMTP id S262640AbVDPLeZ (ORCPT ); Sat, 16 Apr 2005 07:34:25 -0400 Date: Sat, 16 Apr 2005 13:34:46 +0200 From: Thomas Graf To: Herbert Xu Cc: Steven Rostedt , hadi@cyberus.ca, netdev , Tarhon-Onu Victor , kuznet@ms2.inr.ac.ru, devik@cdi.cz, linux-kernel@vger.kernel.org, Patrick McHardy , "David S. Miller" Subject: Re: ACPI/HT or Packet Scheduler BUG? Message-ID: <20050416113446.GJ4114@postel.suug.ch> References: <1113601029.4294.80.camel@localhost.localdomain> <1113601446.17859.36.camel@localhost.localdomain> <1113602052.4294.89.camel@localhost.localdomain> <20050415225422.GF4114@postel.suug.ch> <20050416014906.GA3291@gondor.apana.org.au> <20050416110639.GI4114@postel.suug.ch> <20050416112329.GA31847@gondor.apana.org.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050416112329.GA31847@gondor.apana.org.au> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1141 Lines: 23 * Herbert Xu <20050416112329.GA31847@gondor.apana.org.au> 2005-04-16 21:23 > On Sat, Apr 16, 2005 at 01:06:39PM +0200, Thomas Graf wrote: > > > > It's not completely useless, it speeds up the deletion classful > > qdiscs having some depth. However, it's not worth the locking > > troubles I guess. > > RCU is meant to optimise the common reader path. In this case > that's the packet transmission code. Unfortunately it fails > miserably when judged by that criterion. There is one case where it can do good for latency which is for per flow qdiscs or any other scenarios implying hundreds or thousands of leaf qdiscs where a destroyage of one such qdisc tree will take up quite some cpu to traverse all the classes under dev->queue_lock. I don't have any numbers on this, but I don't completely dislike the method of hiding the qdiscs under the lock and do the expensive traveling unlocked. - 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/