Date: Mon, 7 Jul 2008 13:44:40 +0100 (BST) From: Robert Watson <rwatson@FreeBSD.org> To: Bruce Evans <brde@optusnet.com.au> Cc: FreeBSD Net <freebsd-net@FreeBSD.org>, Andre Oppermann <andre@FreeBSD.org>, Ingo Flaschberger <if@xip.at>, Paul <paul@gtcomm.net> Subject: Re: Freebsd IP Forwarding performance (question, and some info) [7-stable, current, em, smp] Message-ID: <20080707134036.S63144@fledge.watson.org> In-Reply-To: <20080707213356.G7572@besplex.bde.org> References: <4867420D.7090406@gtcomm.net> <ea7b9c170806302050p2a3a5480t29923a4ac2d7c852@mail.gmail.com> <4869ACFC.5020205@gtcomm.net> <4869B025.9080006@gtcomm.net> <486A7E45.3030902@gtcomm.net> <486A8F24.5010000@gtcomm.net> <486A9A0E.6060308@elischer.org> <486B41D5.3060609@gtcomm.net> <alpine.LFD.1.10.0807021052041.557@filebunker.xip.at> <486B4F11.6040906@gtcomm.net> <alpine.LFD.1.10.0807021155280.557@filebunker.xip.at> <486BC7F5.5070604@gtcomm.net> <20080703160540.W6369@delplex.bde.org> <486C7F93.7010308@gtcomm.net> <20080703195521.O6973@delplex.bde.org> <486D35A0.4000302@gtcomm.net> <alpine.LFD.1.10.0807041106591.19613@filebunker.xip.at> <486DF1A3.9000409@gtcomm.net> <alpine.LFD.1.10.0807041303490.20760@filebunker.xip.at> <486E65E6.3060301@gtcomm.net> <alpine.LFD.1.10.0807052356130.2145@filebunker.xip.at> <4871DB8E.5070903@freebsd.org> <20080707191918.B4703@besplex.bde.org> <4871FB66.1060406@freebsd.org> <20080707213356.G7572@besplex.bde.org>
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On Mon, 7 Jul 2008, Bruce Evans wrote:
> I use low-end memory, but on the machine that does 640 kpps it somehow has
> latency almost 4 times as low as on new FreeBSD cluster machines (~42 nsec
> instead of ~150). perfmon (fixed for AXP and A64) and hwpmc report an
> average of 11 k8-dc-misses per sendto() while sending via bge at 640 kpps.
> 11 * 42 accounts for 442 nsec out of the 1562 per packet at this rate. 11 *
> 150 = 1650 would probably make this rate unachievable despite the system
> having 20 times as much CPU and bus.
Since you're doing fine-grained performance measurements of a code path that
interests me a lot, could you compare the cost per-send on UDP for the
following four cases:
(1) sendto() to a specific address and port on a socket that has been bound to
INADDR_ANY and a specific port.
(2) sendto() on a specific address and port on a socket that has been bound to
a specific IP address (not INADDR_ANY) and a specific port.
(3) send() on a socket that has been connect()'d to a specific IP address and
a specific port, and bound to INADDR_ANY and a specific port.
(4) send() on a socket that has been connect()'d to a specific IP address
and a specific port, and bound to a specific IP address (not INADDR_ANY)
and a specific port.
The last of these should really be quite a bit faster than the first of these,
but I'd be interested in seeing specific measurements for each if that's
possible!
Thanks,
Robert N M Watson
Computer Laboratory
University of Cambridge
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