From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rick Jones Subject: Re: Can I limit the number of active tx per TCP socket? Date: Thu, 06 Mar 2014 11:06:04 -0800 Message-ID: <5318C71C.1020807@hp.com> References: <063D6719AE5E284EB5DD2968C1650D6D0F6D3B91@AcuExch.aculab.com> <5318ADB1.5050107@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: David Laight , "netdev@vger.kernel.org" To: Neal Cardwell Return-path: Received: from g4t3427.houston.hp.com ([15.201.208.55]:55905 "EHLO g4t3427.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752153AbaCFTGF (ORCPT ); Thu, 6 Mar 2014 14:06:05 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On 03/06/2014 10:09 AM, Neal Cardwell wrote: > Eric's recent "auto corking" feature may be helpful in this context: > > http://lwn.net/Articles/576263/ Doesn't that depend on the bottleneck being local to the sending side? Perhaps I've mis-understood David's setup, but I get the impression the bottleneck is not at the sending side but either in the middle or at the end, so tx completions will still be happening quickly. rick > neal > > On Thu, Mar 6, 2014 at 12:17 PM, Rick Jones wrote: >> On 03/06/2014 04:28 AM, David Laight wrote: >>> >>> Is it possible to stop a TCP connection having more than one >>> tx skb (in the ethernet tx ring) at any one time? >>> The idea is to allow time for short sends from the application >>> to accumulate so that the transmitted frames are longer. >> >> >> That is precisely what Nagle is supposed to be doing - at least where the >> definition of "time" is the round-trip-time rather than "time it takes to >> get transmitted out the NIC." >> >> >>> Basically I have a TCP connection which carries a lot of separate >>> short 'user buffers'. These are not command-response so >>> TCP_NODELAY has to be set to avoid long delays. >> >> >> When you are saturating the receiver and/or the 64K line, are you certain >> that not setting TCP_NODELAY means long delays? >> >> From a later message: >> >> >>> The data is sent out on a 64k line so 1ms is only 8 byte times. >> >> >> Are you still using a 1460 byte MSS on such a connection? >> >> Perhaps you can set the MSS (or drop the MTU on the 64K line and use PTMU) >> to something less to trigger window updates a bit sooner and so get >> piggy-backed ACKs rather than delayed ACKs and so not have to set >> TCP_NODELAY? Yes, you will have a question of headers versus headers+data >> but with TCP_NODELAY set as you have it you are (probably) already trashing >> that. >> >> Setting TCP_NODELAY to avoid "long delays" and then having a 64Kbyte/s link >> seems a trifle, well, contradictory. >> >> rick jones >> >> -- >> To unsubscribe from this list: send the line "unsubscribe netdev" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >