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.
