Re: [REGRESSION] Perf (userspace) broken on big.LITTLE systems since v6.5

From: Mark Rutland
Date: Tue Nov 21 2023 - 11:03:04 EST

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On Tue, Nov 21, 2023 at 07:46:57AM -0800, Ian Rogers wrote:
> On Tue, Nov 21, 2023 at 7:40 AM Mark Rutland <mark.rutland@xxxxxxx> wrote:
> >
> > On Tue, Nov 21, 2023 at 03:24:25PM +0000, Marc Zyngier wrote:
> > > On Tue, 21 Nov 2023 13:40:31 +0000,
> > > Marc Zyngier <maz@xxxxxxxxxx> wrote:
> > > >
> > > > [Adding key people on Cc]
> > > >
> > > > On Tue, 21 Nov 2023 12:08:48 +0000,
> > > > Hector Martin <marcan@xxxxxxxxx> 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):
> >
> > IIUC the tool is doing the wrong thing here and overriding explicit
> > ${pmu}/${event}/ events with PERF_TYPE_HARDWARE events rather than events using
> > that ${pmu}'s type and event namespace.
> >
> > Regardless of the *new* ABI that allows PERF_TYPE_HARDWARE events to be
> > targetted to a specific PMU, it's semantically wrong to rewrite events like
> > this since ${pmu}/${event}/ is not necessarily equivalent to a similarly-named
> > PERF_COUNT_HW_${EVENT}.
>
> If you name a PMU and an event then the event should only be opened on
> that PMU, 100% agree. There's a bunch of output, but when the legacy
> cycles event is opened it appears to be because it was explicitly
> requested.

I think you've missed that the named PMU events are being erreously transformed
into PERF_TYPE_HARDWARE events. Look at the -vvv output, e.g.

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

... which should not be PERF_TYPE_HARDWARE && PERF_COUNT_HW_CPU_CYCLES.

Marc said that he bisected the issue down to commit:

5ea8f2ccffb23983 ("perf parse-events: Support hardware events as terms")

... so it looks like something is going wrong when the events are being parsed,
e.g. losing the HW PMU information?

Thanks,
Mark.

>
>
> Thanks,
> Ian
>
> > Mark.
> >
> > > <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.

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In reply to: Ian Rogers: "Re: [REGRESSION] Perf (userspace) broken on big.LITTLE systems since v6.5"
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