Messages in this thread | | | Date | Wed, 19 Jun 2013 12:50:39 -0600 | From | David Ahern <> | Subject | Re: [PATCH 0/3] tracing/perf: perf_trace_buf/perf_xxx hacks. |
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On 6/19/13 11:51 AM, Oleg Nesterov wrote: > On 06/19, Oleg Nesterov wrote: >> >> On 06/19, Peter Zijlstra wrote: >>> >>> I'm probably missing something obviuos, but what are we trying to do? >> >> Say, "perf record -e sched:sched_switch -p1". >> >> Every task except /sbin/init will do perf_trace_sched_switch() and >> perf_trace_buf_prepare() + perf_trace_buf_submit for no reason(), >> it doesn't have a counter. > > I did some testing under kvm, not sure these numbers actually mean > something, but still. > > So, the test-case: > > int pipe1[2], pipe2[2]; > > void *tfunc(void *arg) > { > for (;;) { > char c; > assert(read(pipe1[0], &c, 1) == 1); > assert(write(pipe2[1], &c, 1) == 1); > } > } > > int main(void) > { > pthread_t thr; > int nr; > > assert(pipe(pipe1) == 0); > assert(pipe(pipe2) == 0); > > assert(pthread_create(&thr, NULL, tfunc, NULL) == 0); > > for (nr = 0; nr < 1000 * 1000; ++nr) { > char c; > > assert(write(pipe1[1], &c, 1) == 1); > assert(read(pipe2[0], &c, 1) == 1); > } > > return 0; > }
Same as "perf bench sched pipe"
David
> > Idle machine, "/usr/bin/time -f "%e %S %U" taskset 1 ./pf" 3 times: > > 20.73 20.05 0.66 > 20.68 20.04 0.63 > 20.68 20.02 0.65 > > Now with "perf record -e sched:sched_switch -p1" running, > > before 3/3: > > 21.59 20.77 0.80 > 21.40 20.70 0.68 > 21.50 20.72 0.78 > > after 3/3: > > 21.00 20.23 0.76 > 20.89 20.19 0.69 > 20.94 20.26 0.66 > > Oleg. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
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