Re: [PATCH] x86: Run checksumming in parallel accross multiple alu's

[Neil Horman]

On Mon, Oct 28, 2013 at 05:24:38PM +0100, Ingo Molnar wrote:
> 
> * Neil Horman <nhorman@xxxxxxxxxxxxx> wrote:
> 
> > Looking at the specific cpu counters we get this:
> > 
> > Base:
> >      Total time: 0.179 [sec]
> > 
> >  Performance counter stats for 'perf bench sched messaging -- bash -c echo 1 > /sys/module/csum_test/parameters/test_fire' (20 runs):
> > 
> >        1571.304618 task-clock                #    5.213 CPUs utilized            ( +-  0.45% )
> >             14,423 context-switches          #    0.009 M/sec                    ( +-  4.28% )
> >              2,710 cpu-migrations            #    0.002 M/sec                    ( +-  2.83% )
> 
> Hm, for these second round of measurements were you using 'perf stat 
> -a -C ...'?
> 
> The most accurate method of measurement for such single-threaded 
> workloads is something like:
> 
> 	taskset 0x1 perf stat -a -C 1 --repeat 20 ...
> 
> this will bind your workload to CPU#0, and will do PMU measurements 
> only there - without mixing in other CPUs or workloads.
> 
> Thanks,
> 
> 	Ingo
I wasn't, but I will...
Neil

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