On Fri, 2015-05-01 at 11:20 -0400, Rik van Riel wrote:
> On 05/01/2015 02:40 AM, Ingo Molnar wrote:
>
> >> This patch builds on top of these patches by Paolo:
> >> https://lkml.org/lkml/2015/4/28/188
> >> https://lkml.org/lkml/2015/4/29/139
> >>
> >> Together with this patch I posted earlier this week, the syscall path
> >> on a nohz_full cpu seems to be about 10% faster.
> >> https://lkml.org/lkml/2015/4/24/394
> >>
> >> My test is a simple microbenchmark that calls getpriority() in a loop
> >> 10 million times:
> >>
> >> run time system time
> >> vanilla 5.49s 2.08s
> >> __acct patch 5.21s 1.92s
> >> both patches 4.88s 1.71s
> >
> > Just curious, what are the numbers if you don't have context tracking
> > enabled, i.e. without nohz_full?
> >
> > I.e. what's the baseline we are talking about?
>
> It's an astounding difference. This is not a kernel without nohz_full,
> just a CPU without nohz_full running the same kernel I tested with
> yesterday:
>
> run time system time
> vanilla 5.49s 2.08s
> __acct patch 5.21s 1.92s
> both patches 4.88s 1.71s
> CPU w/o nohz 3.12s 1.63s <-- your numbers, mostly
Below are v4.1-rc1-172-g6c3c1eb3c35e + patches measurements.
100M * stat() on isolated cpu
NO_HZ_FULL off inactive housekeeper nohz_full
real 0m14.266s 0m14.367s 0m20.427s 0m27.921s
user 0m1.756s 0m1.553s 0m1.976s 0m10.447s
sys 0m12.508s 0m12.769s 0m18.400s 0m17.464s
(real) 1.000 1.007 1.431 1.957
1.000 1.000
real 0m20.423s 0m27.930s +rik 1,2
user 0m2.072s 0m10.450s
sys 0m18.304s 0m17.471s
vs off 1.431 1.957
vs prev 1.000 1.000
real 0m20.256s 0m27.803s +paolo 1,2 (2
missing prototypes)
user 0m1.884s 0m10.551s
sys 0m18.353s 0m17.242s
vs off 1.419 1.948
vs prev .991 .995
real 0m19.122s 0m26.946s +rik 3
user 0m1.896s 0m10.292s
sys 0m17.198s 0m16.644s
vs off 1.340 1.888
vs prev .944 .969
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