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Date: Mon, 18 May 2009 14:52:33 -0700 (PDT) From: David Miller <davem@...emloft.net> To: jarkao2@...il.com Cc: dada1@...mosbay.com, vexwek@...il.com, netdev@...r.kernel.org, kaber@...sh.net, devik@....cz Subject: Re: HTB accuracy for high speed From: Jarek Poplawski <jarkao2@...il.com> Date: Mon, 18 May 2009 19:23:49 +0200 > On Mon, May 18, 2009 at 06:40:56PM +0200, Eric Dumazet wrote: >> With a typical estimator "1sec 8sec", ewma_log value is 3 >> >> At gigabit speeds, we are very close to overflow yes, since >> we only have 27 bits available, so 134217728 bytes per second >> or 1073741824 bits per second. >> >> So formula : >> e->avbps += ((long)rate - (long)e->avbps) >> e->ewma_log; >> is going to overflow. >> >> One way to avoid the overflow would be to use a smaller estimator, like "500ms 4sec" >> >> Or use a 64bits rate & avbps, this is needed fo 10Gb speeds I suppose... > > Yes, I considered this too, but because of an overhead I decided to > fix as designed (according to the comment) for now. But probably you > are right, and we should go further, so I'm OK with your patch. I like this patch too, Eric can you submit this formally with proper signoffs etc.? Thanks! -- 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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