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Date: Wed, 11 Mar 2009 08:34:23 -0700 From: John Heffner <johnwheffner@...il.com> To: Andi Kleen <andi@...stfloor.org> Cc: David Miller <davem@...emloft.net>, md@....sk, netdev@...r.kernel.org Subject: Re: TCP rx window autotuning harmful at LAN context On Wed, Mar 11, 2009 at 8:01 AM, Andi Kleen <andi@...stfloor.org> wrote: > On Wed, Mar 11, 2009 at 06:30:58AM -0700, David Miller wrote: >> From: Andi Kleen <andi@...stfloor.org> >> Date: Wed, 11 Mar 2009 11:03:35 +0100 >> >> > Perhaps this points to the default buffer sizing heuristics to >> > be too aggressive for >= 1GB? >> >> It's necessary Andi, you can't fill a connection on a trans- >> continental connection without at least a 4MB receive buffer. > > Seems pretty arbitary to me. It's the value for a given bandwidth*latency > product, but why not half or twice the bandwidth? I don't think > that number is written in stone like you claim. It is of course just a number, though not exactly arbitrary -- it's approximately the required value for transcontinental 100 Mbps paths. Choosing the value is a matter of engineering trade-offs, and seemed like a reasonable cap at this time. Any cap so much lower that it would give a small bound for LAN latencies would bring us back to the bad old days where you couldn't get anything more than 10 Mbps on the wide area. -John -- 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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