Re: [Qemu-devel] [PATCH v1] test-coroutine: test cost introduced by coroutine

["Benoît Canet" <benoit.canet@irqsave.net>]

The Wednesday 13 Aug 2014 à 18:08:47 (+0800), Ming Lei wrote :
> This test runs dummy function with coroutine by using
> two enter and one yield since which is a common usage.
> 
> So we can see the cost introduced by corouting for running
> one function, for example:
> 
> 	Run operation 20000000 iterations 4.841071 s, 4131K operations/s
> 	242ns per coroutine
> 
> Signed-off-by: Ming Lei <ming.lei@canonical.com>
> ---
>  tests/test-coroutine.c |   30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/tests/test-coroutine.c b/tests/test-coroutine.c
> index 6e634f4..e22fae1 100644
> --- a/tests/test-coroutine.c
> +++ b/tests/test-coroutine.c
> @@ -311,6 +311,35 @@ static void perf_baseline(void)
>          maxcycles, duration);
>  }
>  
> +static __attribute__((noinline)) void perf_cost_func(void *opaque)
> +{
> +    qemu_coroutine_yield();
> +}
> +
> +static void perf_cost(void)
> +{
> +    const unsigned long maxcycles = 40000000;
> +    unsigned long i = 0;
> +    double duration;
> +    unsigned long ops;
> +    Coroutine *co;
> +
> +    g_test_timer_start();
> +    while (i++ < maxcycles) {
> +        co = qemu_coroutine_create(perf_cost_func);

I am not sure qemu_coroutine_create is systematically used.
I rather believe the code try to reuse existing coroutine.

> +        qemu_coroutine_enter(co, &i);
> +        qemu_coroutine_enter(co, NULL);
> +    }
> +    duration = g_test_timer_elapsed();
> +    ops = (long)(maxcycles / (duration * 1000));
> +
> +    g_test_message("Run operation %lu iterations %f s, %luK operations/s, "
> +                   "%luns per coroutine",
> +                   maxcycles,
> +                   duration, ops,
> +                   (unsigned long)(1000000000 * duration) / maxcycles);
> +}
> +
>  int main(int argc, char **argv)
>  {
>      g_test_init(&argc, &argv, NULL);
> @@ -325,6 +354,7 @@ int main(int argc, char **argv)
>          g_test_add_func("/perf/nesting", perf_nesting);
>          g_test_add_func("/perf/yield", perf_yield);
>          g_test_add_func("/perf/function-call", perf_baseline);
> +        g_test_add_func("/perf/cost", perf_cost);
>      }
>      return g_test_run();
>  }
> -- 
> 1.7.9.5
> 
>