From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ed W Subject: Re: Raise initial congestion window size / speedup slow start? Date: Wed, 14 Jul 2010 19:48:36 +0100 Message-ID: <4C3E0684.5060409@wildgooses.com> References: <4C3D94E3.9080103@wildgooses.com> <4C3DD5EB.9070908@tmr.com> <20100714.111553.104052157.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: davidsen@tmr.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org To: David Miller Return-path: In-Reply-To: <20100714.111553.104052157.davem@davemloft.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 14/07/2010 19:15, David Miller wrote: > From: Bill Davidsen > Date: Wed, 14 Jul 2010 11:21:15 -0400 > > >> You may have to go into /proc/sys/net/core and crank up the >> rmem_* settings, depending on your distribution. >> > You should never, ever, have to touch the various networking sysctl > values to get good performance in any normal setup. If you do, it's a > bug, report it so we can fix it. > Just checking the basics here because I don't think this is a bug so much as a, less common installation that differs from the "normal" case. - When we create a tcp connection we always start with tcp slow start - This sets the congestion window to effectively 4 packets? - This applies in both directions? - Remote sender responds to my hypothetical http request with the first 4 packets of data - We need to wait one RTT for the ack to come back and now we can send the next 8 packets, - Wait for the next ack and at 16 packets we are now moving at a sensible fraction of the bandwidth delay product? So just to be clear: - We don't seem to have any user-space tuning knobs to influence this right now? - In this age of short attention spans, a couple of extra seconds between clicking something and it responding is worth optimising (IMHO) - I think I need to take this to netdev, but anyone else with any ideas happy to hear them? Thanks Ed W