Re: [PATCH 04/15] powerpc/time: Prepare to stop elapsing in dynticks-idle

[Shrikanth Hegde]

Hi Christophe.

> > No. With this patch there will not be any performance difference.
> > All it does is, instead of using mftb uses sched_clock at those places.
>
> For the record, I did some benchmark test with tools/testing/selftests/ 
> powerpc/benchmarks/null_syscall on powerpc 885 microcontroller:
>
> Without your proposed patch:
>
> root@vgoip:~# ./null_syscall
>     2729.98 ns     360.36 cycles
>
> With your proposed patch below:
>
> root@vgoip:~# ./null_syscall
>     3370.80 ns     444.95 cycles
>
> So as expected it is a huge regression, almost 25% more time to run the 
> syscall.
>
> Christophe
>
>
> >

Got it. My bad  in assuming it may not happen multiple before vtime_flush.

Btw, can you try latest vtime_reset patch? It shouldn't make any difference.
I tried perf bench syscall basic, and ./null_syscall.
I don't any difference for vtime_reset patch.