--- Jesper Juhl <jesper.juhl@xxxxxxxxx> wrote:Configuring "preempt" gives lower latency, because then
On 8/21/05, Danial Thom <danial_thom@xxxxxxxxx>Ok, well you'll have to explain this one:
wrote:
I just started fiddling with 2.6.12, andthere
seems to be a big drop-off in performancefrom
2.4.x in terms of networking on auniprocessor
system. Just bridging packets through thedropping
machine, 2.6.12 starts dropping packets at
~100Kpps, whereas 2.4.x doesn't start
until over 350Kpps on the same hardware(2.0Ghz
Opteron with e1000 driver). This is pitiful512
prformance for this hardware. I've
increased the rx ring in the e1000 driver to
with little change (interrupt moderation isset
to 8000 Ints/second). Has "tuning" for MPthere
destroyed UP performance altogether, or is
some tuning parameter that could make a4-fold
difference? All debugging is off and thereare
no messages on the console or in the errorlogs.
The kernel is the standard kernel.org dowloadethernet
config with SMP turned off and the intel
card drivers as modules without any other2.4
changes, which is exactly the config for my
kernels.If you have preemtion enabled you could disable
it. Low latency comes
at the cost of decreased throughput - can't
have both. Also try using
a HZ of 100 if you are currently using 1000,
that should also improve
throughput a little at the cost of slightly
higher latencies.
I doubt that it'll do any huge difference, but
if it does, then that
would probably be valuable info.
"Low latency comes at the cost of decreased
throughput - can't have both"