From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: To: 9fans@cse.psu.edu Subject: Re: [9fans] sendfile interface From: "rob pike, esq." In-Reply-To: <20030224065045.A5493@unicorn.math.spbu.ru> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="upas-dmsjkkcsahvhesqmylctuopjqf" Date: Sun, 23 Feb 2003 19:56:46 -0800 Topicbox-Message-UUID: 6f712ecc-eacb-11e9-9e20-41e7f4b1d025 This is a multi-part message in MIME format. --upas-dmsjkkcsahvhesqmylctuopjqf Content-Disposition: inline Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Not quite what you are after, but we put readv and writev into the library as a step towards putting them into the kernel interface. The notion was to permit scatter-gather I/O in user space by connecting the segments of the I/O request into blocks (Blocks) rather than copying them several times assembling them into blocks. This would also improve the implementation of devmnt. I'm not sure how much work has been done in that direction since that first tentative step. -rob --upas-dmsjkkcsahvhesqmylctuopjqf Content-Type: message/rfc822 Content-Disposition: inline Return-Path: <9fans-admin@cse.psu.edu> Received: from killy.mspring.net ([207.69.231.40] verified) by mail.mightycheese.com (CommuniGate Pro SMTP 3.4.7) with ESMTP-TLS id 501600 for rob@mail.mightycheese.com; Sun, 23 Feb 2003 21:51:28 -0600 Received: from mail.cse.psu.edu (psuvax1.cse.psu.edu [130.203.4.6]) by killy.mspring.net (8.12.5/8.8.6) with ESMTP id h1O3pPXg089834 for ; Sun, 23 Feb 2003 22:51:25 -0500 (EST) Received: from psuvax1.cse.psu.edu (psuvax1.cse.psu.edu [130.203.18.6]) by mail.cse.psu.edu (CSE Mail Server) with ESMTP id 395A019AC3; Sun, 23 Feb 2003 22:51:16 -0500 (EST) Delivered-To: 9fans@cse.psu.edu Received: from unicorn.math.spbu.ru (unicorn.math.spbu.ru [195.19.226.166]) by mail.cse.psu.edu (CSE Mail Server) with ESMTP id 22E7119AAA for <9fans@cse.psu.edu>; Sun, 23 Feb 2003 22:50:48 -0500 (EST) Received: (from vugluskr@localhost) by unicorn.math.spbu.ru (8.9.3/8.9.3) id GAA05530 for 9fans@cse.psu.edu; Mon, 24 Feb 2003 06:50:46 +0300 From: "Roman V. Shaposhnick" To: 9fans@cse.psu.edu Subject: Re: [9fans] sendfile interface Message-ID: <20030224065045.A5493@unicorn.math.spbu.ru> References: <20030220013204.A6122@unicorn.math.spbu.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 1.0pre3i In-Reply-To: <20030220013204.A6122@unicorn.math.spbu.ru> Sender: 9fans-admin@cse.psu.edu Errors-To: 9fans-admin@cse.psu.edu X-BeenThere: 9fans@cse.psu.edu X-Mailman-Version: 2.0.11 Precedence: bulk Reply-To: 9fans@cse.psu.edu List-Id: Fans of the OS Plan 9 from Bell Labs <9fans.cse.psu.edu> List-Archive: Date: Mon, 24 Feb 2003 06:50:45 +0300 Wow! No reply whatsoever :-( Does it mean that it's completely impossible to make sense out of scattered-read hardware (like some network cards for example) under Plan9 ? I understand that performance could be sacrificed for clarity, but was it the case here ? Thanks, Roman. On Thu, Feb 20, 2003 at 01:32:04AM +0300, Roman V. Shaposhnick wrote: > While studying how Linux implements sendfile(2), I couldn't help > but notice, that it is yet another hack a'la mmap. "There must > be a better way to do that" I though at the moment. > > Now, I imagine, that for Plan9 there should be no problem telling > kernel that one Chan should server as an "alias", or proxy if you > will, for another one. By doing that, it should be possible to > eliminate the whole "copy to userland buffer; copy back to kernel" > routine and it could be even possible to utilize hardware > scattered-write. How easy it will be for network connections ? Or may > be I'm stretching my imagination too far, and there's no really > a better way to do it. Please comment. > > Thanks, > Roman. --upas-dmsjkkcsahvhesqmylctuopjqf--