From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261163AbVFJS0D (ORCPT ); Fri, 10 Jun 2005 14:26:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261165AbVFJS0C (ORCPT ); Fri, 10 Jun 2005 14:26:02 -0400 Received: from mustang.oldcity.dca.net ([216.158.38.3]:24033 "HELO mustang.oldcity.dca.net") by vger.kernel.org with SMTP id S261163AbVFJSZz (ORCPT ); Fri, 10 Jun 2005 14:25:55 -0400 Subject: Re: Real-time problem due to IO congestion. From: Lee Revell To: Takashi Ikebe Cc: Jens Axboe , andrea@suse.de, Linux Kernel Mailing List In-Reply-To: <42A94611.8070502@lab.ntt.co.jp> References: <42A91D36.8090506@lab.ntt.co.jp> <20050610062452.GK5140@suse.de> <42A94611.8070502@lab.ntt.co.jp> Content-Type: text/plain Date: Fri, 10 Jun 2005 14:26:46 -0400 Message-Id: <1118428006.6423.5.camel@mindpipe> Mime-Version: 1.0 X-Mailer: Evolution 2.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2005-06-10 at 16:49 +0900, Takashi Ikebe wrote: > Jens Axboe wrote: > > On Fri, Jun 10 2005, Takashi Ikebe wrote: > > > > This basically needs io priorities to work, so that request allocation > > is prioritized as well. I didn't actually add request allocation groups > > in the cfq-ts posted with priority support, however I have some patches > > from years ago that did so. I'll see if I can find the time to brush > > those off. > > > > As you and andrew said, basically application based approach seems > reasonable, > but I'm so interesting your patch, if you have time, please show me :-) Take a look at the lock-free ringbuffers in JACK. No point reinventing the wheel... I think it's a bit strange that the disk IO issue comes up so often in these RT discussions, it's something of a red herring, because there's rarely an RT constraint in getting the data to disk; the RT constraint is in getting the data from the device to memory. Lee