Messages in this thread | | | Date | Wed, 22 Nov 2023 10:06:23 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [REGRESSION] Perf (userspace) broken on big.LITTLE systems since v6.5 |
| |
Em Wed, Nov 22, 2023 at 12:23:27PM +0900, Hector Martin escreveu: > On 2023/11/22 1:38, Ian Rogers wrote: > > On Tue, Nov 21, 2023 at 8:15 AM Mark Rutland <mark.rutland@arm.com> wrote: > >> On Tue, Nov 21, 2023 at 08:09:37AM -0800, Ian Rogers wrote: > >>> On Tue, Nov 21, 2023 at 8:03 AM Mark Rutland <mark.rutland@arm.com> wrote: > >>>> 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@arm.com> 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@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): > >>>>>> > >>>>>> 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? > >>> > >>> Ok, I think I'm getting confused by other things. This looks like the issue. > >>> > >>> I think it may be working as intended, but not how you intended :-) If > >>> a core PMU is listed and then a legacy event, the legacy event should
The point is that "cycles" when prefixed with "pmu/" shouldn't be considered "cycles" as HW/0, in that setting it is "cycles" for that PMU. (but we only have "cpu_cycles" for at least the a53 and a72 PMUs I have access in a Libre Computer rockchip 3399-pc hybrid board, if we use it, then we get what we want/had before, see below):
And there is an attempt at using the specified PMU, see the first perf_event_open:
root@roc-rk3399-pc:~# strace -e perf_event_open perf stat -vv -e cycles,armv8_cortex_a53/cycles/,armv8_cortex_a72/cycles/ echo Using CPUID 0x00000000410fd082 ------------------------------------------------------------ perf_event_attr: type 0 (PERF_TYPE_HARDWARE) config 0x700000000 disabled 1 ------------------------------------------------------------ sys_perf_event_open: pid 0 cpu -1 group_fd -1 flags 0x8perf_event_open({type=PERF_TYPE_HARDWARE, size=0 /* PERF_ATTR_SIZE_??? */, config=0x7<<32|PERF_COUNT_HW_CPU_CYCLES, sample_period=0, sample_type=0, read_format=0, disabled=1, precise_ip=0 /* arbitrary skid */, ...}, 0, -1, -1, PERF_FLAG_FD_CLOEXEC) = -1 ENOENT (No such file or directory) //// HERE: it tries config=0x7<<32|PERF_COUNT_HW_CPU_CYCLES taking into //account the PMU number 0x7
root@roc-rk3399-pc:~# cat /sys/devices/armv8_cortex_a53/type 7 root@roc-rk3399-pc:~#
But then we don't have "cycles" in that PMU:
root@roc-rk3399-pc:~# ls -la /sys/devices/armv8_cortex_a53/events/cycles ls: cannot access '/sys/devices/armv8_cortex_a53/events/cycles': No such file or directory root@roc-rk3399-pc:~#
Maybe:
root@roc-rk3399-pc:~# taskset -c 5,6 perf stat -v -e armv8_cortex_a53/cpu_cycles/,armv8_cortex_a72/cpu_cycles/ echo Using CPUID 0x00000000410fd034 Control descriptor is not initialized
armv8_cortex_a53/cpu_cycles/: 0 2079000 0 armv8_cortex_a72/cpu_cycles/: 2488961 2079000 2079000
Performance counter stats for 'echo':
<not counted> armv8_cortex_a53/cpu_cycles/ (0.00%) 2488961 armv8_cortex_a72/cpu_cycles/
0.003449266 seconds time elapsed
0.003502000 seconds user 0.000000000 seconds sys
root@roc-rk3399-pc:~# taskset -c 0,1,2,3,4 perf stat -v -e armv8_cortex_a53/cpu_cycles/,armv8_cortex_a72/cpu_cycles/ echo Using CPUID 0x00000000410fd034 Control descriptor is not initialized
armv8_cortex_a53/cpu_cycles/: 2986601 6999416 6999416 armv8_cortex_a72/cpu_cycles/: 0 6999416 0
Performance counter stats for 'echo':
2986601 armv8_cortex_a53/cpu_cycles/ <not counted> armv8_cortex_a72/cpu_cycles/ (0.00%)
0.011434508 seconds time elapsed
0.003911000 seconds user 0.007454000 seconds sys
root@roc-rk3399-pc:~#
root@roc-rk3399-pc:~# cat /sys/devices/armv8_cortex_a53/events/cpu_cycles event=0x0011 root@roc-rk3399-pc:~# cat /sys/devices/armv8_cortex_a72/events/cpu_cycles event=0x0011 root@roc-rk3399-pc:~#
And the syscalls seem sane:
root@roc-rk3399-pc:~# strace -e perf_event_open taskset -c 0,1,2,3,4 perf stat -v -e armv8_cortex_a53/cpu_cycles/,armv8_cortex_a72/cpu_cycles/ echo Using CPUID 0x00000000410fd034 Control descriptor is not initialized perf_event_open({type=0x7 /* PERF_TYPE_??? */, size=0x88 /* PERF_ATTR_SIZE_??? */, config=0x11, sample_period=0, sample_type=PERF_SAMPLE_IDENTIFIER, read_format=PERF_FORMAT_TOTAL_TIME_ENABLED|PERF_FORMAT_TOTAL_TIME_RUNNING, disabled=1, inherit=1, enable_on_exec=1, precise_ip=0 /* arbitrary skid */, exclude_guest=1, ...}, 14573, -1, -1, PERF_FLAG_FD_CLOEXEC) = 3 perf_event_open({type=0x8 /* PERF_TYPE_??? */, size=0x88 /* PERF_ATTR_SIZE_??? */, config=0x11, sample_period=0, sample_type=PERF_SAMPLE_IDENTIFIER, read_format=PERF_FORMAT_TOTAL_TIME_ENABLED|PERF_FORMAT_TOTAL_TIME_RUNNING, disabled=1, inherit=1, enable_on_exec=1, precise_ip=0 /* arbitrary skid */, exclude_guest=1, ...}, 14573, -1, -1, PERF_FLAG_FD_CLOEXEC) = 4
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=14573, si_uid=0, si_status=0, si_utime=0, si_stime=0} --- armv8_cortex_a53/cpu_cycles/: 3227098 4480875 4480875 armv8_cortex_a72/cpu_cycles/: 0 4480875 0
Performance counter stats for 'echo':
3227098 armv8_cortex_a53/cpu_cycles/ <not counted> armv8_cortex_a72/cpu_cycles/ (0.00%)
0.008381759 seconds time elapsed
0.004064000 seconds user 0.004121000 seconds sys
--- SIGCHLD {si_signo=SIGCHLD, si_code=SI_USER, si_pid=14572, si_uid=0} --- +++ exited with 0 +++ root@roc-rk3399-pc:~#
As:
root@roc-rk3399-pc:~# cat /sys/devices/armv8_cortex_a53/type 7 root@roc-rk3399-pc:~# cat /sys/devices/armv8_cortex_a72/type 8 root@roc-rk3399-pc:~#
See the type=0x7 and type=0x8.
So what we need here seems to be to translate the generic term "cycles" to "cpu_cycles" when a PMU is explicitely passed in the event name and it doesn't have "cycles" and then just retry.
- Arnaldo
| |