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Date: Mon, 08 Sep 2008 22:17:42 -0700 (PDT) From: David Miller <davem@...emloft.net> To: csnook@...hat.com Cc: rick.jones2@...com, netdev@...r.kernel.org Subject: Re: RFC: Nagle latency tuning From: Chris Snook <csnook@...hat.com> Date: Tue, 09 Sep 2008 01:10:05 -0400 > This is open to debate, but there are certainly a great many apps > doing a great deal of very important business that are subject to > this problem to some degree. Let's be frank and be honest that we're talking about message passing financial service applications. And I specifically know that the problem they run into is that the congestion window doesn't open up because of Nagle _AND_ the fact that congestion control is done using packet counts rather that data byte totals. So if you send lots of small stuff, the window doesn't open. Nagle just makes this problem worse, rather than create it. And we have a workaround for them, which is a combination of the tcp_slow_start_after_idle sysctl in combination with route metrics specifying the initial congestion window value to use. I specifically added that sysctl for this specific situation. Really, the situation here is well established and I highly encourage you to take a deeper look into the actual problems being hit, and show us some specific traces we can analyze properly if the problem is still there. Otherwise we're just shooting into the wind without any specifics to work on whatsoever. -- 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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