Re: em driver worse then fxp driver ... why?

From: Eli Dart (dart_at_nersc.gov)
Date: 08/10/04

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    To: "Marc G. Fournier" <scrappy@hub.org>
Date: Tue, 10 Aug 2004 14:09:33 -0700

    In reply to "Marc G. Fournier" <scrappy@hub.org> :

    >
    > I have 5 servers sitting on a Linksys 10/100 switch ... 4 of the 5 are
    > running fxp0 ethernet, while the 5th is running em ... and the 5th
    > performs atrociously:
    >
    > neptune# netstat -ni | head
    > Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Co
     ll
    > em0 1500 <Link#1> 00:07:e9:05:1b:2e 36915965 10306 28888840 1 10858
     513
    >
    > I've tried in bth half and full duplex mode .. full duplex, Ierrs climbs, hal
     f-duplex, Collisions climb ...

    I would expect collisions on a half-duplex link -- this is not
    necessarily a Bad Thing.

    It could be that the unmanaged switch is unable to talk full-duplex
    to the em interface for some reason.....

    Do you have throughput numbers for the two configs (half-duplex em,
    full-duplex em, and full-duplex fxp)?

                    --eli

    >
    > the fxp devices are all running at full-duplex, and perform quite well:
    >
    > pluto# netstat -ni | head
    > Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Co
     ll
    > fxp0 1500 <Link#1> 00:03:47:bd:67:66 105856025 0 97330263 2
     0
    > jupiter# netstat -ni | head
    > Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Co
     ll
    > fxp0 1500 <Link#1> 00:03:47:30:a7:1b 28832141 0 29437148 0 0
    > mars# netstat -ni | head
    > Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Co
     ll
    > fxp0 1500 <Link#1> 00:e0:81:21:d7:f6 34195201 0 29871571 0 0
    > venus# netstat -ni | head
    > Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Co
     ll
    > fxp0 1500 <Link#1> 00:e0:81:29:56:5b 95579278 1 87014732 1 0
    >
    > Originally, it was explained that unmanaged switches tended to be
    > problematic, but I'd expect some sort of uniformity in problems, but 'just
    > the server with the em device' ...
    >
    > So, is there a bug in the em device driver that doesn't exist on the fxp0
    > devices?
    >
    >
    > ----
    > Marc G. Fournier Hub.Org Networking Services (http://www.hub.org)
    > Email: scrappy@hub.org Yahoo!: yscrappy ICQ: 7615664
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