From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 10 Dec 2001 16:15:10 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 10 Dec 2001 16:15:00 -0500 Received: from cx97923-a.phnx3.az.home.com ([24.1.197.194]:48831 "EHLO grok.yi.org") by vger.kernel.org with ESMTP id ; Mon, 10 Dec 2001 16:14:51 -0500 Message-ID: <3C1525C7.1030408@candelatech.com> Date: Mon, 10 Dec 2001 14:14:47 -0700 From: Ben Greear Organization: Candela Technologies User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:0.9.4) Gecko/20011019 Netscape6/6.2 X-Accept-Language: en-us MIME-Version: 1.0 To: root@chaos.analogic.com CC: linux-kernel Subject: Re: min-write-size for a UDP socket to be POLLOUT cannot be set. (proposed fixes) In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Richard B. Johnson wrote: > On Mon, 10 Dec 2001, Ben Greear wrote: >>I have 4M queue size. I have 4M-2k bytes already in the >>queue (2k free). I have a 4k UDP buffer to write. I call >>select and it says the socket is writable. However, in this >>case I cannot actually write to the socket because I have only >>2 of the 4k that I need... Now, I can detect the failure to send >>and re-transmit, but that basically gets me into a tight loop because >>select keeps saying I can write, and I keep trying. The tight loop >>is doubly bad because the machine is already highly stressed or it's >>buffers would never be so full.... >> >>I want select to only say I can write when I'm at XX (say, 64k) bytes of >>free buffer-queue space... >> >>Ben >> >> > > If you have a 4M queue size, it appears as though you are trying to > use UDP where TCP should have been used. Normally, what you call the > queue size, is set to contain you largest packet you will ever want to > send. With this in mind, you don't even know if a fragmented packet > can be routed if it's more than 64k in length so you would never try > to send something larger than that under UDP. Assume that I actually want to do what I said I did! :) I never try to send a packet bigger than 64k, the protocol doesn't handle it. But, I may try to send 100000 60k UDP packets in very fast succession...which could fill up my send queue. -- Ben Greear President of Candela Technologies Inc http://www.candelatech.com ScryMUD: http://scry.wanfear.com http://scry.wanfear.com/~greear