linux-kernel - RE: [RFC PATCH] x86/CPU/AMD: Bring back Compute Unit ID

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Date:   Thu, 2 Feb 2017 16:14:54 +0000
From:   "Ghannam, Yazen" <Yazen.Ghannam@....com>
To:     Borislav Petkov <bp@...en8.de>
CC:     x86-ml <x86@...nel.org>, Yves Dionne <yves.dionne@...il.com>,
        Brice Goglin <Brice.Goglin@...ia.fr>,
        Peter Zijlstra <peterz@...radead.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: RE: [RFC PATCH] x86/CPU/AMD: Bring back Compute Unit ID

> -----Original Message-----
> From: Borislav Petkov [mailto:bp@...en8.de]
> Sent: Thursday, February 2, 2017 7:11 AM
> 
> Context switches have dropped, cache misses are the same and we have a
> rise in cpu-migrations. That last bit is interesting and I don't have an
> answer yet. Maybe peterz has an idea.
> 

Could it be that the scheduler is more lax about migrations between SMT
siblings?

> Cycles have dropped too.
> 
> And we're 6 secs faster so I'll take that.
> 
> Now on to run the same thing on a bigger bulldozer.
> 

Here are my results on a 32C Bulldozer system with an SSD. Also, I use ccache so
I added "ccache -C" in the pre-build script so the cache gets cleared.

Before:
Performance counter stats for 'make -s -j65 bzImage' (3 runs):

    2375752.777479      task-clock (msec)         #   23.589 CPUs utilized            ( +-  0.35% )
         1,198,979      context-switches          #    0.505 K/sec                    ( +-  0.34% )
     8,964,671,259      cache-misses                                                  ( +-  0.44% )
            79,399      cpu-migrations            #    0.033 K/sec                    ( +-  1.92% )
        37,840,875      page-faults               #    0.016 M/sec                    ( +-  0.20% )
 5,425,612,846,538      cycles                    #    2.284 GHz                      ( +-  0.36% )
 3,367,750,745,825      instructions              #    0.62  insn per cycle                                              ( +-  0.11% )
   750,591,286,261      branches                  #  315.938 M/sec                    ( +-  0.11% )
    43,544,059,077      branch-misses             #    5.80% of all branches          ( +-  0.08% )

     100.716043494 seconds time elapsed                                          ( +-  1.97% )

After:
Performance counter stats for 'make -s -j65 bzImage' (3 runs):

    1736720.488346      task-clock (msec)         #   23.529 CPUs utilized            ( +-  0.16% )
         1,144,737      context-switches          #    0.659 K/sec                    ( +-  0.20% )
     8,570,352,975      cache-misses                                                  ( +-  0.33% )
            91,817      cpu-migrations            #    0.053 K/sec                    ( +-  1.67% )
        37,688,118      page-faults               #    0.022 M/sec                    ( +-  0.03% )
 5,547,082,899,245      cycles                    #    3.194 GHz                      ( +-  0.19% )
 3,363,365,420,405      instructions              #    0.61  insn per cycle                                              ( +-  0.00% )
   749,676,420,820      branches                  #  431.662 M/sec                    ( +-  0.00% )
    43,243,046,270      branch-misses             #    5.77% of all branches          ( +-  0.01% )

      73.810517234 seconds time elapsed                                          ( +-  0.02% )

Thanks,
Yazen