Hi Rik,
On Wed, 2016-02-10 at 20:08 -0500, r...@redhat.com wrote:
> I tested this series with a microbenchmark calling
> an invalid syscall number ten million times in a row,
> on a nohz_full cpu.
>
> Run times for the microbenchmark:
>
> 4.4 3.8 seconds
> 4.5-rc1 3.7 seconds
> 4.5-rc1 + first patch 3.3 seconds
> 4.5-rc1 + first 3 patches 3.1 seconds
> 4.5-rc1 + all patches 2.3 seconds
>
> Same test on a non-NOHZ_FULL, non-housekeeping CPU:
> all kernels 1.86 seconds
I tested 10M stat(".", &buf) calls, and saw a win of ~20% on a
nohz_full cpu. Below are nopreempt vs nohz_full+patches overhead
numbers from my box.
avg
4.4.1-nopreempt 0m1.652s 0m1.633s 0m1.635s 1.640 1.000
nohz_full + patches
nohz_full inactive 0m1.642s 0m1.631s 0m1.629s 1.634 .996
housekeeper CPU 0m2.013s 0m2.012s 0m2.033s 2.019 1.231
nohz_full CPU 0m2.247s 0m2.233s 0m2.239s 2.239 1.365
It still ain't free ;-) but between this set, and all the other work
that has gone in ~recently, it looks one hell of a lot better. That's
not too scary a pricetag.
-Mike
