Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 6 Feb 2001 13:10:37 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 6 Feb 2001 13:10:27 -0500 Received: from nat-pool.corp.redhat.com ([199.183.24.200]:59482 "EHLO devserv.devel.redhat.com") by vger.kernel.org with ESMTP id ; Tue, 6 Feb 2001 13:10:25 -0500 Date: Tue, 6 Feb 2001 13:09:09 -0500 (EST) From: Ben LaHaise To: Jens Axboe cc: "Stephen C. Tweedie" , Linus Torvalds , Alan Cox , Manfred Spraul , Steve Lord , , , Ingo Molnar Subject: Re: [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait In-Reply-To: <20010206190018.E580@suse.de> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 6 Feb 2001, Jens Axboe wrote: > Stephen already covered this point, the merging is not a problem > to deal with for read-ahead. The underlying system can easily I just wanted to make sure that was clear =) > queue that in nice big chunks. Delayed allocation makes it > easier to to flush big chunks as well. I seem to recall the xfs people > having problems with the lack of merging causing a performance hit > on smaller I/O. That's where readaround buffers come into play. If we have a fixed number of readaround buffers that are used when small ios are issued, they should provide a low overhead means of substantially improving things like find (which reads many nearby inodes out of order but sequentially). I need to implement this can get cache hit rates for various workloads. ;-) > Of course merging doesn't have to happen in ll_rw_blk. > > > As for io completion, can't we just issue seperate requests for the > > critical data and the readahead? That way for SCSI disks, the important > > io should be finished while the readahead can continue. Thoughts? > > Priorities? Definately. I'd like to be able to issue readaheads with a "don't bother executing if this request unless the cost is low" bit set. It might also be helpful for heavy multiuser loads (or even a single user with multiple processes) to ensure progress is made for others. -ben - 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/