Re: 2.6.12 Performance problems

Danial Thom
2005-08-25T14:26:49Z

--- Ben Greear <greearb@candelatech.com> wrote:

> Danial Thom wrote:
> >
> > --- Ben Greear <greearb@candelatech.com>
> wrote:
> >
> >
> >>Danial Thom wrote:
> >>
> >>
> >>>I think the concensus is that 2.6 has made
> >>
> >>trade
> >>
> >>>offs that lower raw throughput, which is
> what
> >>
> >>a
> >>
> >>>networking device needs. So as a router or
> >>>network appliance, 2.6 seems less suitable.
> A
> >>
> >>raw
> >>
> >>>bridging test on a 2.0Ghz operton system:
> >>>
> >>>FreeBSD 4.9: Drops no packets at 900K pps
> >>>Linux 2.4.24: Starts dropping packets at
> 350K
> >>
> >>pps
> >>
> >>>Linux 2.6.12: Starts dropping packets at
> 100K
> >>
> >>pps
> >>
> >>I ran some quick tests using kernel 2.6.11,
> 1ms
> >>tick (HZ=1000), SMP kernel.
> >>Hardware is P-IV 3.0Ghz + HT on a new
> >>SuperMicro motherboard with 64/133Mhz
> >>PCI-X bus. NIC is dual Intel pro/1000.
> Kernel
> >>is close to stock 2.6.11.
> >>
> >>I used brctl to create a bridge with the two
> >>GigE adapters in it and
> >>used pktgen to stream traffic through it
> >>(250kpps in one direction, 1kpps in
> >>the other.)
> >>
> >>I see a reasonable amount of drops at 250kpps
> >>(60 byte packets):
> >>about 60,000,000 packets received, 20,700
> >>dropped.
>
> I get slightly worse performance on this system
> when running RH9
> with kernel 2.4.29 (my hacks, HZ=1000, SMP).
> Tried increasing
> e1000 descriptors to 2048 tx and rx, but that
> didn't help, or at least
> not much.
>
> Will try some other tunings, but I doubt it
> will affect performance
> enough to come close to the discrepency that
> you show between 2.4
> and 2.6 kernels...
>
> I tried copying a 500MB CDROM to HD on my RH9
> system, and only 6kpps
> of the 250kpps get through the bridge...btw.

The tests I reported where on UP systems. Perhaps
the default settings are better for this in 2.4,
since that is what I used, and you used your
hacks for both.

Are you getting drops or overruns (or both)? I
would assume drops is a decision to drop rather
than an overrun which is a ring overrun. Overruns
would imply more about performance than tuning,
I'd think.

I wouldn't think that HT would be appropriate for
this sort of setup...?

You're using a dual PCI-X NIC rather than the
onboard ports? Supermicro runs their onboard
controllers at 32bit/33mhz for some mindless
reason.

Danial

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