Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756483AbXFVVLw (ORCPT ); Fri, 22 Jun 2007 17:11:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752066AbXFVVLp (ORCPT ); Fri, 22 Jun 2007 17:11:45 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:53214 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751998AbXFVVLo (ORCPT ); Fri, 22 Jun 2007 17:11:44 -0400 Date: Fri, 22 Jun 2007 23:10:32 +0200 From: Ingo Molnar To: Christoph Hellwig , Linus Torvalds , Steven Rostedt , LKML , Andrew Morton , Thomas Gleixner , john stultz , Oleg Nesterov , "Paul E. McKenney" , Dipankar Sarma , "David S. Miller" , matthew.wilcox@hp.com, kuznet@ms2.inr.ac.ru Subject: Re: [RFC PATCH 0/6] Convert all tasklets to workqueues Message-ID: <20070622211032.GA17607@elte.hu> References: <20070622040014.234651401@goodmis.org> <20070622204058.GA11777@elte.hu> <20070622210013.GA1353@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070622210013.GA1353@infradead.org> User-Agent: Mutt/1.5.14 (2007-02-12) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.1.7 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1135 Lines: 27 * Christoph Hellwig wrote: > Note that we also have a lot of inefficiency in the way we do deferred > processing. Think of a setup where you run a XFS filesystem runs over > a megaraid adapter. > > (1) we get a real hardirq, which just clears the interrupt and then > deferes to a tasklet > (2) tasklet walks the producer / consumer queue and then calls scsi_done > for each completeted scsi command which ends up doing > raise_softirq_irqoff(BLOCK_SOFTIRQ); > (3) block softirq does the heavy lifting for command completion and finally > calls back into the bio's completion routine > (4) xfs wants to avoid irq safe locking and thus deferes the command to a > kthread i dont understand - why is a tasklet used at all? Why not do it straight in the BLOCK_SOFTIRQ? Using tasklets there is extra, unnecessary overhead already. Ingo - 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/