From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 18 Jan 2001 05:02:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 18 Jan 2001 05:02:28 -0500 Received: from [24.65.192.120] ([24.65.192.120]:15090 "EHLO webber.adilger.net") by vger.kernel.org with ESMTP id ; Thu, 18 Jan 2001 05:02:18 -0500 From: Andreas Dilger Message-Id: <200101181001.f0IA11I25258@webber.adilger.net> Subject: Re: Is sendfile all that sexy? In-Reply-To: <200101180823.JAA18205@cave.bitwizard.nl> "from Rogier Wolff at Jan 18, 2001 09:23:15 am" To: Rogier Wolff Date: Thu, 18 Jan 2001 03:01:01 -0700 (MST) CC: Linus Torvalds , linux-kernel@vger.kernel.org X-Mailer: ELM [version 2.4ME+ PL73 (25)] MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Roger Wolff writes: > I'd prefer an interface that says "copy this fd to that one, and > optimize that if you can". > > For example, copying a file from one disk to another. I'm pretty sure > that some efficiency can be gained if you don't need to handle the > possibility of the userspace program accessing the data in between the > read and the write. Sure this may not qualify as a "trivial > optimization, that can be done with the existing infrastructure" right > now, but programs that want to indicate "kernel, please optimize this > if you can" can say so. Actually, this is a great example, because at one point I was working on a device interface which would offload all of the disk-disk copying overhead to the disks themselves, and not involve the CPU/RAM at all. I seem to recall that I2O promised something along these lines as well (i.e. direct device-device communication). Cheers, Andreas -- Andreas Dilger \ "If a man ate a pound of pasta and a pound of antipasto, \ would they cancel out, leaving him still hungry?" http://www-mddsp.enel.ucalgary.ca/People/adilger/ -- Dogbert - 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/