Date: Mon, 26 Jul 2004 16:28:56 -0400 From: Don Bowman <don@sandvine.com> To: 'Luigi Rizzo' <rizzo@icir.org>, Kelly Yancey <kbyanc@posi.net> Cc: 'James' <haesu@towardex.com> Subject: RE: device polling takes more CPU hits?? Message-ID: <FE045D4D9F7AED4CBFF1B3B813C85337051D9445@mail.sandvine.com>
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From: Luigi Rizzo [mailto:rizzo@icir.org] > On Mon, Jul 26, 2004 at 01:18:46PM -0700, Kelly Yancey wrote: > ... > > Out of curiousity, what sort of testing did you do to > arrive at these > > settings? I did some testing a while back with a SmartBits > box pumping > > packets through a FreeBSD 2.8Ghz box configured to route > between two em > > gigabit interfaces; I found that changing the burst_max and > each_burst > > parameters had almost no effect on throughput (maximum 1% > difference). > > fast boxes are pci-bus limited, not CPU limited(*) so > changing the burst > size (which basically amortizes some CPU costs) has little if any > effect. The PCI-X bus will probably be 64-bit 133MHz in this case, the limit moves up to the P64H2 hub for large packets, to the CPU for small packets. Polling becomes quite critical to prevent livelock. --don
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