Re: [PATCH 3/5] perf core: Prepare writing into ring buffer from end

[Peter Zijlstra]

On Fri, Mar 25, 2016 at 10:14:36PM +0800, Wangnan (F) wrote:
> >>I think you enabled some unusual config options?

x86_64-defconfig

> >You must enabled CONFIG_OPTIMIZE_INLINING. Now I get similar result:

It has that indeed.

> After enabling CONFIG_OPTIMIZE_INLINING:
> 
> Test its performance by calling 'close(-1)' for 3000000 times and
> use 'perf record -o /dev/null -e raw_syscalls:* test-ring-buffer' to
> capture system calls:
> 
>                   MEAN         STDVAR
> BASE            800077.1     23448.13
> RAWPERF.PRE    2465858.0    603473.70
> RAWPERF.POST   2471925.0    609437.60
> 
> Considering the high stdvar, after applying this patch the performance
> is not change.

Why is your variance so immense? And doesn't that render the
measurements pointless?