发自我的 iPhone
> 在 2016年3月27日，下午11:20，Peter Zijlstra <pet...@infradead.org> 写道： > > 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? > For some unknown reason, about 10% of these results raises 2 times of normal results. Say, "normal results" are about 2200000, but those "outliers" are about 4400000 (I can't access raw data now). Variance becomes much smaller if I remove those outliers. I guess the outliers is caused by some type of lock stepping? No clue about it. Thank you.
