From: Milian Wolff <milian.wolff@kdab.com>
To: linux-perf-users@vger.kernel.org
Cc: acme@kernel.org, jiri@infradead.org, namhyung@kernel.org
Subject: non matching read_format: perf script fails when combining sampling group with trace event
Date: Mon, 15 Jan 2018 17:33:09 +0100 [thread overview]
Message-ID: <2474046.gKqmCbzhgQ@milian-kdab2> (raw)
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Hey all,
I've spotted this strange behavior:
$ perf record -e '{cycles,instructions}:PS' -e sched:sched_switch --switch-
events sleep 1
trace-cmd: No such file or directory
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.014 MB perf.data (15 samples) ]
$ perf script --show-switch-events
trace-cmd: No such file or directory
non matching read_format
When I use 'cycles' instead of '{cycles,instructions}', the above works as
expected:
$ perf record -e 'cycles:PS' -e sched:sched_switch --switch-events sleep 1
trace-cmd: No such file or directory
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.013 MB perf.data (8 samples) ]
$ perf script --show-switch-events
trace-cmd: No such file or directory
perf 9777 457715.655901: 281474975716438 cycles:PS:
ffffffff8105ef84 native_write_msr ([kernel.kallsyms])
perf 9777 457715.655904: 281474975714469 cycles:PS:
ffffffff8105ef84 native_write_msr ([kernel.kallsyms])
perf 9777 457715.655905: 281474975712795 cycles:PS:
ffffffff8105ef84 native_write_msr ([kernel.kallsyms])
perf 9777 457715.655907: 281474975712801 cycles:PS:
ffffffff8105ef84 native_write_msr ([kernel.kallsyms])
perf 9777 457715.655908: 281474975712804 cycles:PS:
ffffffff8105ef84 native_write_msr ([kernel.kallsyms])
perf 9777 457715.655911: 281474975717052 cycles:PS:
ffffffff813079e6 memcpy_erms ([kernel.kallsyms])
sleep 9777 457715.655946: 281474975838141 cycles:PS:
ffffffff8120b2da __fput ([kernel.kallsyms])
sleep 9777 [002] 457715.656254: sched:sched_switch:
prev_comm=sleep prev_pid=9777 prev_prio=120 prev_state=S ==>
next_comm=swapper/2 next_pid=0 next_prio=120
sleep 9777 457715.656254: PERF_RECORD_SWITCH OUT
sleep 9777 457716.656361: PERF_RECORD_SWITCH IN
Can someone explain what's going on here? This smells like a bug to me.
Thanks
--
Milian Wolff | milian.wolff@kdab.com | Senior Software Engineer
KDAB (Deutschland) GmbH, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt, C++ and OpenGL Experts
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