Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 21 Nov 2000 07:00:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 21 Nov 2000 07:00:50 -0500 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:58245 "EHLO fgwmail5.fujitsu.co.jp") by vger.kernel.org with ESMTP id ; Tue, 21 Nov 2000 07:00:42 -0500 From: kumon@flab.fujitsu.co.jp Date: Tue, 21 Nov 2000 20:30:33 +0900 Message-Id: <200011211130.UAA27961@asami.proc.flab.fujitsu.co.jp> To: Jens Axboe Cc: kumon@flab.fujitsu.co.jp, linux-kernel@vger.kernel.org, Dave Jones , Andrea Arcangeli Subject: Re: [PATCH] livelock in elevator scheduling In-Reply-To: <20001121112836.B10007@suse.de> In-Reply-To: <200011210838.RAA27382@asami.proc.flab.fujitsu.co.jp> <20001121112836.B10007@suse.de> Reply-To: kumon@flab.fujitsu.co.jp Cc: kumon@flab.fujitsu.co.jp X-Mailer: Handmade Mailer version 1.0 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Jens Axboe writes: > > Problem: > > Current elevator_linus() traverses the I/O requesting queue from the > > tail to top. And when the current request has smaller sector number > > than the request on the top of queue, it is always placed just after > > the top. > > This means, if requests in some sector range are continuously > > generated, a request with larger sector number is always places at the > > last and has no chance to go to the front. e.g. it is not scheduled. > > Believe it or not, but this is intentional. In that regard, the > function name is a misnomer -- call it i/o scheduler instead :-) I never believe it intentional. If it is true, the current kernel will be suffered from a kind of DOS attack. Yes, actually I'm a victim of it. By Running ZD's ServerBench, not only the performance down, but my machine blocks all commands execution including /bin/ps, /bin/ls... , and those are not ^C able unless the benchmark is stopped. Those commands are read from disks but the requests are wating at the end of I/O queue, those won't be executed. Anyway, I'll try your patch. -- Computer Systems Laboratory, Fujitsu Labs. kumon@flab.fujitsu.co.jp - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/