Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751261AbWHMObh (ORCPT ); Sun, 13 Aug 2006 10:31:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751264AbWHMObh (ORCPT ); Sun, 13 Aug 2006 10:31:37 -0400 Received: from brick.kernel.dk ([62.242.22.158]:57640 "EHLO kernel.dk") by vger.kernel.org with ESMTP id S1751261AbWHMObh (ORCPT ); Sun, 13 Aug 2006 10:31:37 -0400 Date: Sun, 13 Aug 2006 16:31:35 +0200 From: Jens Axboe To: Andrew Morton Cc: linux-kernel@vger.kernel.org Subject: Re: softirq considered harmful Message-ID: <20060813143135.GB3245@suse.de> References: <20060810110627.GM11829@suse.de> <20060812162857.d85632b9.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060812162857.d85632b9.akpm@osdl.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1544 Lines: 40 On Sat, Aug 12 2006, Andrew Morton wrote: > On Thu, 10 Aug 2006 13:06:27 +0200 > Jens Axboe wrote: > > > Ok maybe that is a little too strong, but I am indeed seeing some very > > sucky behaviour with softirqs here. The block layer uses it for doing > > request completions > > I wasn't even aware that this change had been made. I don't recall (and I > cannot locate) any mailing list discussion of it. > > Maybe I missed the discussion. But if not, this is yet another case of > significant changes getting into mainline via a git merge and sneaking > under everyone's radar. It's not a significant change, it pretty much falls into a code relocation issue. The softirq completion stuff was made generic, and SCSI the primary user of it. The completion path didn't change for SCSI. > It seems like a bad idea to me. Any additional latency at all in disk > completion adds directly onto process waiting time - we do a _lot_ of > synchronous disk IO. Doesn't seem like a good idea to me either, hence I'm investigating the current possible problems with it... > There is no mention in the changelog of any observed problems which this > patch solves. Can we revert it please? As you should see now, it wont change anything. The problem would be the same. -- Jens Axboe - 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/