Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964902AbXBLMWk (ORCPT ); Mon, 12 Feb 2007 07:22:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964897AbXBLMWk (ORCPT ); Mon, 12 Feb 2007 07:22:40 -0500 Received: from relay.2ka.mipt.ru ([194.85.82.65]:38175 "EHLO 2ka.mipt.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964880AbXBLMWj (ORCPT ); Mon, 12 Feb 2007 07:22:39 -0500 Date: Mon, 12 Feb 2007 15:19:40 +0300 From: Evgeniy Polyakov To: Andi Kleen Cc: David Miller , Ulrich Drepper , Andrew Morton , netdev , Zach Brown , Christoph Hellwig , Chase Venters , Johann Borck , linux-kernel@vger.kernel.org, Jeff Garzik , Jamal Hadi Salim , Ingo Molnar , linux-fsdevel@vger.kernel.org Subject: Re: [take36 10/10] kevent: Kevent based generic AIO. Message-ID: <20070212121940.GA31252@2ka.mipt.ru> References: <11712796493850@2ka.mipt.ru> <1171279650540@2ka.mipt.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=koi8-r Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.9i X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-1.7.5 (2ka.mipt.ru [0.0.0.0]); Mon, 12 Feb 2007 15:20:08 +0300 (MSK) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1738 Lines: 36 On Mon, Feb 12, 2007 at 02:08:10PM +0100, Andi Kleen (ak@suse.de) wrote: > Evgeniy Polyakov writes: > > > > aio_sendfile_path() is essentially aio_sendfile(), except that it takes > > source filename as parameter, has a pointer to private header > > and its size (which allows to send header and file's content in one syscall > > instead of three (open, send, sendfile) and returns opened file descriptor. > > Are you sure this is a useful optimization? Do you have numbers vs open+aio_sendfile+close? > > Compared to the cost of sending a complete file three system calls should be quite in the noise. > And Linux system calls are not that expensive (few hundred cycles normally) > > Adding such compound system calls would be a worrying precedent because > I'm sure others would want them then for their favourite system call combo > too. If they were really useful it might make more sense to have a batch() > system call that works for arbitary calls, but I'm not convinced yet > it's even needed. It would be certainly ugly. Yes, that call ends up about 10MB/sec faster for 100 1mb file transfers over 1gbit network (78 MB/s vs 66-72 MB/s over 1 Gb network, sendfile sending server is one-way AMD Athlong 64 3500+), but indeed, it can be the case that async IO sending was main speed factor. I added header by request from Suparna Bhattacharya - my main position is the same about syscall overhead, but I do not that care. > -Andi -- Evgeniy Polyakov - 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/