Messages in this thread |  | | From | Nadav Amit <> | | Subject | Problem running perf using Intel-PT with snapshots | | Date | Wed, 17 May 2023 21:26:28 -0700 |
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Hello perf masters,
I am running perf with Intel PT with snapshot mode and the result makes no sense. I tried to figure it out myself but failed.
Excluding the first data file, the rest seem messed up in various ways. The only thing that repeatedly shows are calls to __fentry__+0x0. I would note that ftrace is not enabled, and I turned off mitigations as I thought it might somehow be related, but it did not help.
Here is an example for execution and output. In between I ran `kill -SIGUSR2 [perf-pid]`. To dump some traces.
Any ideas what it might be?
Thanks, Nadav
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$ perf record -e intel_pt/noretcomp=1/k --kcore --timestamp -a --snapshot=e262144 --switch-output -m,64 [ perf record: dump data: Woken up 2 times ] [ perf record: Dump perf.data.2023051804132358 ] [ perf record: dump data: Woken up 1 times ] [ perf record: Dump perf.data.2023051804132537 ] [ perf record: dump data: Woken up 1 times ] [ perf record: Dump perf.data.2023051804132689 ] ^C[ perf record: Woken up 1 times to write data ] [ perf record: Dump perf.data.2023051804132829 ] [ perf record: Captured and wrote 14.330 MB perf.data.<timestamp> ]
$ sudo perf script -i perf.data.2023051804004293
:-1 -1 [006] 78.287624: 1 branches:k: ffffffff81096125 ept_page_fault+0x3f5 ([kernel.kallsyms]) => ffffffff8108f1d0 kvm_mmu_get_child_sp+0x0 ([kernel.kallsyms]) :-1 -1 [006] 78.287624: 1 branches:k: ffffffff8108f1d0 kvm_mmu_get_child_sp+0x0 ([kernel.kallsyms]) => ffffffff81131190 __fentry__+0x0 ([kernel.kallsyms]) instruction trace error type 1 time 78.287624064 cpu 6 pid -1 tid -1 ip 0xffffffff8101c4fd code 6: Trace doesn't match instruction :-1 -1 [006] 78.287624: 1 branches:k: ffffffff81296e14 futex_unlock_pi+0x184 ([kernel.kallsyms]) => ffffffff81294120 futex_cmpxchg_value_locked+0x0 ([kernel.kallsyms]) :-1 -1 [006] 78.287624: 1 branches:k: ffffffff81294124 futex_cmpxchg_value_locked+0x4 ([kernel.kallsyms]) => ffffffff81131190 __fentry__+0x0 ([kernel.kallsyms]) instruction trace error type 1 time 78.287624104 cpu 6 pid -1 tid -1 ip 0xffffffff824c7a44 code 6: Trace doesn't match instruction :-1 -1 [006] 78.287624: 1 branches:k: ffffffff812909c4 __tick_broadcast_oneshot_control+0x1d4 ([kernel.kallsyms]) => ffffffff8128f720 tick_broadcast_set_event+0x0 ([kernel.kallsyms]) :-1 -1 [006] 78.287624: 1 branches:k: ffffffff8128f720 tick_broadcast_set_event+0x0 ([kernel.kallsyms]) => ffffffff81131190 __fentry__+0x0 ([kernel.kallsyms]) :-1 -1 [006] 78.287624: 1 branches:k: ffffffff81296e8e futex_unlock_pi+0x1fe ([kernel.kallsyms]) => ffffffff812961d0 put_pi_state+0x0 ([kernel.kallsyms]) :-1 -1 [006] 78.287624: 1 branches:k: ffffffff812961d4 put_pi_state+0x4 ([kernel.kallsyms]) => ffffffff81131190 __fentry__+0x0 ([kernel.kallsyms]) instruction trace error type 1 time 78.287624208 cpu 6 pid -1 tid -1 ip 0xffffffff824c7a44 code 6: Trace doesn't match instruction
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