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Subject[PATCH v2 0/3] perf/core: expose thread context switch out event type to user space
Date

Implementation of exposing context-switch-out type event as a part
of PERF_RECORD_SWITCH[_CPU_WIDE] record.

Introduced types of events assumed to be:
a) preempt: when task->state == TASK_RUNNING
b) yield: !preempt, encoding is done using new bit
PERF_RECORD_MISC_SWITCH_OUT_YIELD like this:

event_header->misc &=
PERF_RECORD_MISC_SWITCH_OUT|PERF_RECORD_MISC_SWITCH_OUT_YIELD

Perf tool report and script commands output has been extended to decode
new yield bit and the updated output looks like in the examples below.

The documentation has been updated to mention yield switch out events
and its decoding symbols in perf script output.

The changes have been manually tested on Fedora 27 with the patched kernel:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git perf/core

perf report -D -i system-wide.perf | grep _SWITCH:

1 113807080924003 0x26db26 [0x28]: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 20495/20495
1 113807080925644 0x26db4e [0x28]: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 31479/31479
1 113807080937266 0x26db76 [0x28]: PERF_RECORD_SWITCH_CPU_WIDE OUT yield next pid/tid: 16/16
1 113807080938445 0x26db9e [0x28]: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 20495/20495
1 113807080945455 0x26dbc6 [0x28]: PERF_RECORD_SWITCH_CPU_WIDE OUT yield next pid/tid: 20495/20495

perf script --show-switch-events -F +misc -I -i system-wide.perf:

rcu_sched 8 [003] 113800.748548: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0
perf 31479 [000] S 113800.748548: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 59/59
kworker/0:1 59 [000] 113800.748549: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 31479/31479
rcu_sched 8 [003] Sy 113800.748551: PERF_RECORD_SWITCH_CPU_WIDE OUT yield next pid/tid: 0/0
swapper 0 [003] 113800.748551: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 8/8

---
Alexey Budankov (3):
perf/core: store context switch out type into Perf trace
perf report: extend raw dump (-D) out with switch out event type
perf script: extend misc field decoding with switch out event type

include/uapi/linux/perf_event.h | 5 +++++
kernel/events/core.c | 4 +++-
tools/include/uapi/linux/perf_event.h | 5 +++++
tools/perf/Documentation/perf-script.txt | 17 +++++++++--------
tools/perf/builtin-script.c | 5 ++++-
tools/perf/util/event.c | 4 +++-
6 files changed, 29 insertions(+), 11 deletions(-)

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