RE: device polling takes more CPU hits??

From: Kelly Yancey (kbyanc_at_posi.net)
Date: 07/27/04

  • Next message: Julian Elischer: "Re: PPPoE problem: "Too many LQR packets lost"" 
    Date: Mon, 26 Jul 2004 20:00:10 -0700 (PDT)
To: Don Bowman <don@sandvine.com>

    On Mon, 26 Jul 2004, Don Bowman wrote:

    > 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.
    >

      Sorry, I should be been more clear. Polling certainly stopped livelock
    under extreme load, however I never found much difference whether the
    burst size was small or large. I was wondering if it was just the nature
    of my test and if in other environments the burst_max and each_burst knobs
    have a greater affect.

      Kelly 

    --
Kelly Yancey  -  kbyanc@{posi.net,FreeBSD.org}  -  kelly@nttmcl.com
FreeBSD, The Power To Serve: http://www.freebsd.org/
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  • Next message: Julian Elischer: "Re: PPPoE problem: "Too many LQR packets lost""

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