Re: 回复：[PATCH] perf: optimize clear page in Intel specified model with movq instruction

[Luming Yu]

On Mon, Oct 18, 2021 at 8:43 PM Borislav Petkov <bp@xxxxxxxxx> wrote:
>
> On Mon, Oct 18, 2021 at 03:43:46PM +0800, JY Ni wrote:
> > _*Precondition:*__*do tests on a Intel CPX server.*_ CPU information of my
> > test machine is in backup part._*
>
> My machine:
>
> processor       : 0
> vendor_id       : GenuineIntel
> cpu family      : 6
> model           : 106
> stepping        : 4
>
> That's a SKYLAKE_X.
>
> I ran
>
> ./tools/perf/perf stat --repeat 5 --sync --pre=/root/bin/pre-build-kernel.sh -- make -s -j96 bzImage
>
> on -rc6, building allmodconfig each of the 10 times.
>
> pre-build-kernel.sh is
>
> ---
> #!/bin/bash
>
> make -s clean
> echo 3 > /proc/sys/vm/drop_caches
> ---
>
> Results are below but to me that's all "in the noise" with around one
> percent if I can trust the stddev. Which is not even close to 40%.
>
> So basically you're wasting your time.
>
> 5.15-rc6
> --------
>
> # ./tools/perf/perf stat --repeat 5 --sync --pre=/root/bin/pre-build-kernel.sh -- make -s -j96 bzImage
>
>  Performance counter stats for 'make -s -j96 bzImage' (5 runs):
>
>       3,072,392.92 msec task-clock                #   51.109 CPUs utilized            ( +-  0.05% )
>          1,351,534      context-switches          #  440.257 /sec                     ( +-  0.99% )
>            224,862      cpu-migrations            #   73.248 /sec                     ( +-  1.39% )
>         85,073,723      page-faults               #   27.712 K/sec                    ( +-  0.01% )
>  8,743,357,421,495      cycles                    #    2.848 GHz                      ( +-  0.06% )
>  7,643,946,991,468      instructions              #    0.88  insn per cycle           ( +-  0.00% )
>  1,705,128,638,240      branches                  #  555.440 M/sec                    ( +-  0.00% )
>     37,637,576,027      branch-misses             #    2.21% of all branches          ( +-  0.03% )
> 22,511,903,971,150      slots                     #    7.333 G/sec                    ( +-  0.03% )
>  7,377,211,958,188      topdown-retiring          #     32.5% retiring                ( +-  0.02% )
>  3,145,247,374,138      topdown-bad-spec          #     13.9% bad speculation         ( +-  0.27% )
>  8,018,664,899,041      topdown-fe-bound          #     35.2% frontend bound          ( +-  0.07% )
>  4,167,103,609,622      topdown-be-bound          #     18.3% backend bound           ( +-  0.09% )
>
>             60.114 +- 0.112 seconds time elapsed  ( +-  0.19% )
>
>
>
> 5.15-rc6 + patch
> ----------------
>
>  Performance counter stats for 'make -s -j96 bzImage' (5 runs):
>
>       3,033,250.65 msec task-clock                #   51.243 CPUs utilized            ( +-  0.05% )
>          1,329,033      context-switches          #  438.210 /sec                     ( +-  0.64% )
>            225,550      cpu-migrations            #   74.369 /sec                     ( +-  1.36% )
>         85,080,938      page-faults               #   28.053 K/sec                    ( +-  0.00% )
>  8,629,663,367,477      cycles                    #    2.845 GHz                      ( +-  0.05% )
>  7,696,237,813,803      instructions              #    0.89  insn per cycle           ( +-  0.00% )
>  1,709,909,494,107      branches                  #  563.793 M/sec                    ( +-  0.00% )
>     37,719,552,337      branch-misses             #    2.21% of all branches          ( +-  0.02% )
> 22,214,249,023,820      slots                     #    7.325 G/sec                    ( +-  0.06% )
>  7,412,342,725,008      topdown-retiring          #     33.0% retiring                ( +-  0.01% )
>  3,141,090,408,028      topdown-bad-spec          #     14.1% bad speculation         ( +-  0.17% )
>  7,996,077,873,517      topdown-fe-bound          #     35.6% frontend bound          ( +-  0.03% )
>  3,862,154,886,962      topdown-be-bound          #     17.3% backend bound           ( +-  0.28% )
>
>             59.193 +- 0.302 seconds time elapsed  ( +-  0.51% )

I'm trying to duplicate the difference and get noticed that  time && perf stat
might have a different scale view about the real time spent on the job.

And jiayu.ni's time diff showed the best at 32 jobs and the worst at 96 jobs.

[linux-5.15-rc6]# time make -s bzImage -j96

real    1m8.922s
user    55m25.750s
sys     7m30.666s

[linux-5.15-rc6]# make -s clean

[linux-5.15-rc6]# perf stat  make -s bzImage -j96
..
      61.461679693 seconds time elapsed


    2756.927852000 seconds user
     369.365209000 seconds sys

If kbuild time that jiayu.ni has shared  is not a solid proof for the
optimization idea can be accepted,
we can try other clear_page heavy workloads.

>
> --
> Regards/Gruss,
>     Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette