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Message-Id: <200903111102.31599.remi.denis-courmont@nokia.com> Date: Wed, 11 Mar 2009 11:02:31 +0200 From: "Rémi Denis-Courmont" <remi.denis-courmont@...ia.com> To: ext Marian Ďurkovič <md@....sk> Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org> Subject: Re: TCP rx window autotuning harmful at LAN context On Monday 09 March 2009 13:25:21 ext Marian Ďurkovič wrote: > The behaviour could be descibed as "spiraling death" syndrome. While > TCP with constant and decently sized rx window natively reduces > transmission rate when RTT increases, autotuning performs exactly the > opposite - as a response to increased RTT it increases the rx window size > (which in turn again increases RTT...) As this happens again and again, the > result is complete waste of all available buffers at sending host or at the > bottleneck point, resulting in upto 267 msec (!) latency in LAN context > (with 100 Mbps ethernet connection, default txqueuelen=1000, MTU=1500 and > sky2 driver). Needles to say that this means the LAN is almost unusable. This is very likely a stupid question, but anyway... Is this with all applications, or only some pathological ones (one of which we both wrote code for, alright) with abnormally large send buffers? -- Rémi Denis-Courmont Maemo Software, Nokia Devices R&D -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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