Date: Thu, 13 Apr 2006 21:34:46 +0100 From: David Malone <dwmalone@maths.tcd.ie> To: Dan Nelson <dnelson@allantgroup.com> Cc: freebsd-bugs@FreeBSD.org Subject: Re: kern/75122: [PATCH] Incorrect inflight bandwidth calculation on first packet Message-ID: <20060413203446.GA21222@walton.maths.tcd.ie> In-Reply-To: <200502080720.j187KGr5038302@freefall.freebsd.org> References: <200502080720.j187KGr5038302@freefall.freebsd.org>
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Hi Dan, A couple of questions on the patch: > Index: tcp_hostcache.c I guess the hostcache stuff isn't actually part of the inflight limiting changes? > + if (tp->snd_bandwidth == 0) > + tp->snd_bandwidth = tcp_inflight_min; Unless I'm wrong, this code doesn't make a lot of sense. It is trying to stop the bandwidth estimate being too small after startup/idle. However, snd_bandwidth is in units of bandwidth, but tcp_inflight_min is a window size in bytes. Do you know if this is being triggered much? I'm not sure this if statement will actually help inflight limiting deal with corner cases like this anyway - the tcp_inflight_min already stops it doing too much damage in situations where TCP has been transmitting a low (or zero) rate stream and suddenly wants to start sending more. (Since inflight limiting uses an rttbest including the varience and then averages that with the current rtt estimate, it should not be that close to the edge?) David.
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