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Date:   Tue, 21 Nov 2023 15:24:25 +0000
Message-ID: <86o7fnyvrq.wl-maz@kernel.org>
From:   Marc Zyngier <maz@kernel.org>
To:     Mark Rutland <mark.rutland@arm.com>,
        Hector Martin <marcan@marcan.st>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Ian Rogers <irogers@google.com>,
        James Clark <james.clark@arm.com>
Cc:     linux-perf-users@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        Asahi Linux <asahi@lists.linux.dev>
Subject: Re: [REGRESSION] Perf (userspace) broken on big.LITTLE systems since v6.5
In-Reply-To: <86pm03z0kw.wl-maz@kernel.org>
References: <08f1f185-e259-4014-9ca4-6411d5c1bc65@marcan.st>
        <86pm03z0kw.wl-maz@kernel.org>
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On Tue, 21 Nov 2023 13:40:31 +0000,
Marc Zyngier <maz@kernel.org> wrote:
> 
> [Adding key people on Cc]
> 
> On Tue, 21 Nov 2023 12:08:48 +0000,
> Hector Martin <marcan@marcan.st> wrote:
> > 
> > Perf broke on all Apple ARM64 systems (tested almost everything), and
> > according to maz also on Juno (so, probably all big.LITTLE) since v6.5.
> 
> I can confirm that at least on 6.7-rc2, perf is pretty busted on any
> asymmetric ARM platform. It isn't clear what criteria is used to pick
> the PMU, but nothing works anymore.
> 
> The saving grace in my case is that Debian still ships a 6.1 perftool
> package, but that's obviously not going to last.
> 
> I'm happy to test potential fixes.

At Mark's request, I've dumped a couple of perf (as of -rc2) runs with
-vvv.  And it is quite entertaining (this is taskset to an 'icestorm'
CPU):

<quote>
maz@valley-girl:~/hot-poop/arm-platforms/tools/perf$ sudo taskset -c 0 ./perf stat -vvv -e apple_icestorm_pmu/cycles/ -e
 apple_firestorm_pmu/cycles/ -e cycles ls
Using CPUID 0x00000000612f0280
Attempt to add: apple_icestorm_pmu/cycles=0/
..after resolving event: apple_icestorm_pmu/cycles=0/
Opening: unknown-hardware:HG
------------------------------------------------------------
perf_event_attr:
  type                             0 (PERF_TYPE_HARDWARE)
  config                           0xb00000000
  disabled                         1
------------------------------------------------------------
sys_perf_event_open: pid 0  cpu -1  group_fd -1  flags 0x8
sys_perf_event_open failed, error -95
Attempt to add: apple_firestorm_pmu/cycles=0/
..after resolving event: apple_firestorm_pmu/cycles=0/
Control descriptor is not initialized
Opening: apple_icestorm_pmu/cycles/
------------------------------------------------------------
perf_event_attr:
  type                             0 (PERF_TYPE_HARDWARE)
  size                             136
  config                           0 (PERF_COUNT_HW_CPU_CYCLES)
  sample_type                      IDENTIFIER
  read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
  disabled                         1
  inherit                          1
  enable_on_exec                   1
  exclude_guest                    1
------------------------------------------------------------
sys_perf_event_open: pid 1045843  cpu -1  group_fd -1  flags 0x8 = 3
Opening: apple_firestorm_pmu/cycles/
------------------------------------------------------------
perf_event_attr:
  type                             0 (PERF_TYPE_HARDWARE)
  size                             136
  config                           0 (PERF_COUNT_HW_CPU_CYCLES)
  sample_type                      IDENTIFIER
  read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
  disabled                         1
  inherit                          1
  enable_on_exec                   1
  exclude_guest                    1
------------------------------------------------------------
sys_perf_event_open: pid 1045843  cpu -1  group_fd -1  flags 0x8 = 4
Opening: cycles
------------------------------------------------------------
perf_event_attr:
  type                             0 (PERF_TYPE_HARDWARE)
  size                             136
  config                           0 (PERF_COUNT_HW_CPU_CYCLES)
  sample_type                      IDENTIFIER
  read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
  disabled                         1
  inherit                          1
  enable_on_exec                   1
  exclude_guest                    1
------------------------------------------------------------
sys_perf_event_open: pid 1045843  cpu -1  group_fd -1  flags 0x8 = 5
arch			builtin-diff.o      builtin-mem.o	 common-cmds.h    perf-completion.sh
bench			builtin-evlist.c    builtin-probe.c	 CREDITS	  perf.h
Build			builtin-evlist.o    builtin-probe.o	 design.txt	  perf-in.o
builtin-annotate.c	builtin-ftrace.c    builtin-record.c	 dlfilters	  perf-iostat
builtin-annotate.o	builtin-ftrace.o    builtin-record.o	 Documentation    perf-iostat.sh
builtin-bench.c		builtin.h	    builtin-report.c	 FEATURE-DUMP	  perf.o
builtin-bench.o		builtin-help.c      builtin-report.o	 include	  perf-read-vdso.c
builtin-buildid-cache.c  builtin-help.o      builtin-sched.c	 jvmti		  perf-sys.h
builtin-buildid-cache.o  builtin-inject.c    builtin-script.c	 libapi	  PERF-VERSION-FILE
builtin-buildid-list.c	builtin-inject.o    builtin-script.o	 libperf	  perf-with-kcore
builtin-buildid-list.o	builtin-kallsyms.c  builtin-stat.c	 libsubcmd	  pmu-events
builtin-c2c.c		builtin-kallsyms.o  builtin-stat.o	 libsymbol	  python
builtin-c2c.o		builtin-kmem.c      builtin-timechart.c  Makefile	  python_ext_build
builtin-config.c	builtin-kvm.c	    builtin-top.c	 Makefile.config  scripts
builtin-config.o	builtin-kvm.o	    builtin-top.o	 Makefile.perf    tests
builtin-daemon.c	builtin-kwork.c     builtin-trace.c	 MANIFEST	  trace
builtin-daemon.o	builtin-list.c      builtin-version.c	 perf		  ui
builtin-data.c		builtin-list.o      builtin-version.o	 perf-archive	  util
builtin-data.o		builtin-lock.c      check-headers.sh	 perf-archive.sh
builtin-diff.c		builtin-mem.c	    command-list.txt	 perf.c
apple_icestorm_pmu/cycles/: -1: 0 873709 0
apple_firestorm_pmu/cycles/: -1: 0 873709 0
cycles: -1: 0 873709 0
apple_icestorm_pmu/cycles/: 0 873709 0
apple_firestorm_pmu/cycles/: 0 873709 0
cycles: 0 873709 0

 Performance counter stats for 'ls':

     <not counted>      apple_icestorm_pmu/cycles/                                              (0.00%)
     <not counted>      apple_firestorm_pmu/cycles/                                             (0.00%)
     <not counted>      cycles                                                                  (0.00%)

       0.000002250 seconds time elapsed

       0.000000000 seconds user
       0.000000000 seconds sys
</quote>

If I run the same thing on another CPU cluster (firestorm), I get
this:

<quote>
maz@valley-girl:~/hot-poop/arm-platforms/tools/perf$ sudo taskset -c 2 ./perf stat -vvv -e apple_icestorm_pmu/cycles/ -e
 apple_firestorm_pmu/cycles/ -e cycles ls
Using CPUID 0x00000000612f0280
Attempt to add: apple_icestorm_pmu/cycles=0/
..after resolving event: apple_icestorm_pmu/cycles=0/
Opening: unknown-hardware:HG
------------------------------------------------------------
perf_event_attr:
  type                             0 (PERF_TYPE_HARDWARE)
  config                           0xb00000000
  disabled                         1
------------------------------------------------------------
sys_perf_event_open: pid 0  cpu -1  group_fd -1  flags 0x8
sys_perf_event_open failed, error -95
Attempt to add: apple_firestorm_pmu/cycles=0/
..after resolving event: apple_firestorm_pmu/cycles=0/
Control descriptor is not initialized
Opening: apple_icestorm_pmu/cycles/
------------------------------------------------------------
perf_event_attr:
  type                             0 (PERF_TYPE_HARDWARE)
  size                             136
  config                           0 (PERF_COUNT_HW_CPU_CYCLES)
  sample_type                      IDENTIFIER
  read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
  disabled                         1
  inherit                          1
  enable_on_exec                   1
  exclude_guest                    1
------------------------------------------------------------
sys_perf_event_open: pid 1045925  cpu -1  group_fd -1  flags 0x8 = 3
Opening: apple_firestorm_pmu/cycles/
------------------------------------------------------------
perf_event_attr:
  type                             0 (PERF_TYPE_HARDWARE)
  size                             136
  config                           0 (PERF_COUNT_HW_CPU_CYCLES)
  sample_type                      IDENTIFIER
  read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
  disabled                         1
  inherit                          1
  enable_on_exec                   1
  exclude_guest                    1
------------------------------------------------------------
sys_perf_event_open: pid 1045925  cpu -1  group_fd -1  flags 0x8 = 4
Opening: cycles
------------------------------------------------------------
perf_event_attr:
  type                             0 (PERF_TYPE_HARDWARE)
  size                             136
  config                           0 (PERF_COUNT_HW_CPU_CYCLES)
  sample_type                      IDENTIFIER
  read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
  disabled                         1
  inherit                          1
  enable_on_exec                   1
  exclude_guest                    1
------------------------------------------------------------
sys_perf_event_open: pid 1045925  cpu -1  group_fd -1  flags 0x8 = 5
arch			builtin-diff.o      builtin-mem.o	 common-cmds.h    perf-completion.sh
bench			builtin-evlist.c    builtin-probe.c	 CREDITS	  perf.h
Build			builtin-evlist.o    builtin-probe.o	 design.txt	  perf-in.o
builtin-annotate.c	builtin-ftrace.c    builtin-record.c	 dlfilters	  perf-iostat
builtin-annotate.o	builtin-ftrace.o    builtin-record.o	 Documentation    perf-iostat.sh
builtin-bench.c		builtin.h	    builtin-report.c	 FEATURE-DUMP	  perf.o
builtin-bench.o		builtin-help.c      builtin-report.o	 include	  perf-read-vdso.c
builtin-buildid-cache.c  builtin-help.o      builtin-sched.c	 jvmti		  perf-sys.h
builtin-buildid-cache.o  builtin-inject.c    builtin-script.c	 libapi	  PERF-VERSION-FILE
builtin-buildid-list.c	builtin-inject.o    builtin-script.o	 libperf	  perf-with-kcore
builtin-buildid-list.o	builtin-kallsyms.c  builtin-stat.c	 libsubcmd	  pmu-events
builtin-c2c.c		builtin-kallsyms.o  builtin-stat.o	 libsymbol	  python
builtin-c2c.o		builtin-kmem.c      builtin-timechart.c  Makefile	  python_ext_build
builtin-config.c	builtin-kvm.c	    builtin-top.c	 Makefile.config  scripts
builtin-config.o	builtin-kvm.o	    builtin-top.o	 Makefile.perf    tests
builtin-daemon.c	builtin-kwork.c     builtin-trace.c	 MANIFEST	  trace
builtin-daemon.o	builtin-list.c      builtin-version.c	 perf		  ui
builtin-data.c		builtin-list.o      builtin-version.o	 perf-archive	  util
builtin-data.o		builtin-lock.c      check-headers.sh	 perf-archive.sh
builtin-diff.c		builtin-mem.c	    command-list.txt	 perf.c
apple_icestorm_pmu/cycles/: -1: 1035101 469125 469125
apple_firestorm_pmu/cycles/: -1: 1035035 469125 469125
cycles: -1: 1034653 469125 469125
apple_icestorm_pmu/cycles/: 1035101 469125 469125
apple_firestorm_pmu/cycles/: 1035035 469125 469125
cycles: 1034653 469125 469125

 Performance counter stats for 'ls':

         1,035,101      apple_icestorm_pmu/cycles/                                            
         1,035,035      apple_firestorm_pmu/cycles/                                           
         1,034,653      cycles                                                                

       0.000001333 seconds time elapsed

       0.000000000 seconds user
       0.000000000 seconds sys
</quote>

which doesn't make any sense either. I really don't understand what
this PERF_TYPE_HARDWARE does here (the *real* types are 10 and 11),
nor what this 'cycle=0' stuff is.

/puzzled

	M.

-- 
Without deviation from the norm, progress is not possible.