Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760746Ab0GSRIa (ORCPT ); Mon, 19 Jul 2010 13:08:30 -0400 Received: from g4t0015.houston.hp.com ([15.201.24.18]:20201 "EHLO g4t0015.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753705Ab0GSRI1 (ORCPT ); Mon, 19 Jul 2010 13:08:27 -0400 Message-ID: <4C448688.1070507@hp.com> Date: Mon, 19 Jul 2010 10:08:24 -0700 From: Rick Jones User-Agent: Mozilla/5.0 (X11; U; HP-UX 9000/785; en-US; rv:1.7.13) Gecko/20060601 X-Accept-Language: en-us, en MIME-Version: 1.0 To: "H.K. Jerry Chu" CC: Patrick McManus , David Miller , davidsen@tmr.com, lists@wildgooses.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Subject: Re: Raise initial congestion window size / speedup slow start? References: <4C3D94E3.9080103@wildgooses.com> <4C3DD5EB.9070908@tmr.com> <20100714.111553.104052157.davem@davemloft.net> <1279299709.2156.5814.camel@tng> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1444 Lines: 31 H.K. Jerry Chu wrote: > On Fri, Jul 16, 2010 at 10:01 AM, Patrick McManus wrote: >>can you tell us more about the impl concerns of initcwnd stored on the >>route? > > > We have found two issues when altering initcwnd through the ip route cmd: > 1. initcwnd is actually capped by sndbuf (i.e., tcp_wmem[1], which is > defaulted to a small value of 16KB). This problem has been made obscured > by the TSO code, which fudges the flow control limit (and could be a bug by > itself). I'll ask my Emily Litella question of the day and inquire as to why that would be unique to altering initcwnd via the route? The slightly less Emily Litella-esque question is why an appliction with a desire to know it could send more than 16K at one time wouldn't have either asked via its install docs to have the minimum tweaked (certainly if one is already tweaking routes...), or "gone all the way" and made an explicit setsockopt(SO_SNDBUF) call? We are in a realm of applications for which there was a proposal to allow them to pick their own initcwnd right? Having them pick an SO_SNDBUF size would seem to be no more to ask. rick jones sendbuf_init = max(tcp_mem,initcwnd)? -- 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/