Re: [PATCH] x86: Run checksumming in parallel accross multiple alu's
From: Ingo Molnar
Date: Thu Oct 31 2013 - 06:22:12 EST
* Neil Horman <nhorman@xxxxxxxxxxxxx> wrote:
> > etc. For such short runtimes make sure the last column displays
> > close to 100%, so that the PMU results become trustable.
> > A nehalem+ PMU will allow 2-4 events to be measured in parallel,
> > plus generics like 'cycles', 'instructions' can be added 'for free'
> > because they get counted in a separate (fixed purpose) PMU register.
> > The last colum tells you what percentage of the runtime that
> > particular event was actually active. 100% (or empty last column)
> > means it was active all the time.
> > Thanks,
> > Ingo
> I ran this test:
> for i in `seq 0 1 3`
> echo $i > /sys/module/csum_test/parameters/module_test_mode
> taskset -c 0 perf stat --repeat 20 -C 0 -e L1-dcache-load-misses -e L1-dcache-prefetches -e cycles -e instructions -ddd ./test.sh
You need to remove '-ddd' which is a shortcut for a ton of useful
events, but here you want to use fewer events, to increase the
precision of the measurement.
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