Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 6 Feb 2001 14:14:54 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 6 Feb 2001 14:14:44 -0500 Received: from nat-pool.corp.redhat.com ([199.183.24.200]:8829 "EHLO devserv.devel.redhat.com") by vger.kernel.org with ESMTP id ; Tue, 6 Feb 2001 14:14:31 -0500 Date: Tue, 6 Feb 2001 14:11:23 -0500 (EST) From: Ben LaHaise To: Ingo Molnar cc: "Stephen C. Tweedie" , Linus Torvalds , Alan Cox , Manfred Spraul , Steve Lord , Linux Kernel List , , Ingo Molnar Subject: Re: [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait In-Reply-To: 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, Ingo Molnar wrote: > > On Tue, 6 Feb 2001, Ben LaHaise wrote: > > > - reduce the overhead in submitting block ios, especially for > > large ios. Look at the %CPU usages differences between 512 byte > > blocks and 4KB blocks, this can be better. > > my system is already submitting 4KB bhs. If anyone's raw-IO setup submits > 512 byte bhs thats a problem of the raw IO code ... > > > - make asynchronous io possible in the block layer. This is > > impossible with the current ll_rw_block scheme and io request > > plugging. > > why is it impossible? s/impossible/unpleasant/. ll_rw_blk blocks; it should be possible to have a non blocking variant that does all of the setup in the caller's context. Yes, I know that we can do it with a kernel thread, but that isn't as clean and it significantly penalises small ios (hint: databases issue *lots* of small random ios and a good chunk of large ios). > > You mentioned non-spindle base io devices in your last message. Take > > something like a big RAM disk. Now compare kiobuf base io to buffer > > head based io. Tell me which one is going to perform better. > > roughly equal performance when using 4K bhs. And a hell of a lot more > complex and volatile code in the kiobuf case. I'm willing to benchmark you on this. -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/