TSO4 network problems and scheduler selection

[Jack Vogel]

I had our test/validation group attempt to repro your problem
with TSO and they were unable to do so. I do not know what
hardware/config ingredients in your environment are causing
a problem but something odd is going on.  Test suggested
something like a speed mismatch, but we don't know for
sure.

Right now I see no evidence to suggest that its important
to disable TSO. If anyone has a scenario I can reproduce
I'd be happy to look further.

Jack


On 10/5/07, Artem Kuchin <matrix at itlegion.ru> wrote:
> Hi!
>
> A couple of weeks ago i have written about TSO4 problems on em
> network interface. The problem was that when TSO4 is enable
> em stream send perfomace drop to about ZERO. (i cannot download
> any file from ftp, i canont even get midnight commander to draw
> a full screen in ssh client). Noone has found any solution and
> it was decided that it was a bug in em driver.
>
> Today i have played with SCHED_ULE scheduler on this box
> (it is 7-CURRENT, Pentium D). Adn accidentaly found out that
> when SCHED_ULE is selected TSO4 does not cause any problems.
>
> My interface:
>
> em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
>         options=18b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWCSUM,TSO4>
>
>
> This is totally weird, but i'm letting everybody know it if
> someone step into this problem. Viva SCHED_ULE!
>
> --
> Regards,
> Artem
>
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