[PATCH v6 0/8] perf record --off-cpu: Dump off-cpu samples directly

[Howard Chu <howardchu95@gmail.com>]

Changes in v6:
 - Make patches bisectable

Changes in v5:
 - Delete unnecessary copy in BPF program
 - Remove sample_embed from perf header, hard code off-cpu stuff instead
 - Move evsel__is_offcpu_event() to evsel.h
 - Minor changes to the test
 - Edit some comments

Changes in v4:
 - Minimize the size of data output by perf_event_output()
 - Keep only one off-cpu event
 - Change off-cpu threshold's unit to microseconds
 - Set a default off-cpu threshold
 - Print the correct error message for the field 'embed' in perf data header

Changes in v3:
 - Add off-cpu-thresh argument
 - Process direct off-cpu samples in post

Changes in v2:
 - Remove unnecessary comments.
 - Rename function off_cpu_change_type to off_cpu_prepare_parse

v1:

As mentioned in: https://bugzilla.kernel.org/show_bug.cgi?id=207323

Currently, off-cpu samples are dumped when perf record is exiting. This
results in off-cpu samples being after the regular samples. This patch
series makes possible dumping off-cpu samples on-the-fly, directly into
perf ring buffer. And it dispatches those samples to the correct format
for perf.data consumers.

Before:
```
     migration/0      21 [000] 27981.041319: 2944637851    cycles:P:  ffffffff90d2e8aa record_times+0xa ([kernel.kallsyms])
            perf  770116 [001] 27981.041375:          1    cycles:P:  ffffffff90ee4960 event_function+0xf0 ([kernel.kallsyms])
            perf  770116 [001] 27981.041377:          1    cycles:P:  ffffffff90c184b1 intel_bts_enable_local+0x31 ([kernel.kallsyms])
            perf  770116 [001] 27981.041379:      51611    cycles:P:  ffffffff91a160b0 native_sched_clock+0x30 ([kernel.kallsyms])
     migration/1      26 [001] 27981.041400: 4227682775    cycles:P:  ffffffff90d06a74 wakeup_preempt+0x44 ([kernel.kallsyms])
     migration/2      32 [002] 27981.041477: 4159401534    cycles:P:  ffffffff90d11993 update_load_avg+0x63 ([kernel.kallsyms])

sshd  708098 [000] 18446744069.414584:     286392 offcpu-time: 
	    79a864f1c8bb ppoll+0x4b (/usr/lib/libc.so.6)
	    585690935cca [unknown] (/usr/bin/sshd)
```

After:
```
            perf  774767 [003] 28178.033444:        497           cycles:P:  ffffffff91a160c3 native_sched_clock+0x43 ([kernel.kallsyms])
            perf  774767 [003] 28178.033445:     399440           cycles:P:  ffffffff91c01f8d nmi_restore+0x25 ([kernel.kallsyms])
         swapper       0 [001] 28178.036639:  376650973           cycles:P:  ffffffff91a1ae99 intel_idle+0x59 ([kernel.kallsyms])
         swapper       0 [003] 28178.182921:  348779378           cycles:P:  ffffffff91a1ae99 intel_idle+0x59 ([kernel.kallsyms])
    blueman-tray    1355 [000] 28178.627906:  100184571 offcpu-time: 
	    7528eef1c39d __poll+0x4d (/usr/lib/libc.so.6)
	    7528edf7d8fd [unknown] (/usr/lib/libglib-2.0.so.0.8000.2)
	    7528edf1af95 g_main_context_iteration+0x35 (/usr/lib/libglib-2.0.so.0.8000.2)
	    7528eda4ab86 g_application_run+0x1f6 (/usr/lib/libgio-2.0.so.0.8000.2)
	    7528ee6aa596 [unknown] (/usr/lib/libffi.so.8.1.4)
	    7fff24e862d8 [unknown] ([unknown])


    blueman-tray    1355 [000] 28178.728137:  100187539 offcpu-time: 
	    7528eef1c39d __poll+0x4d (/usr/lib/libc.so.6)
	    7528edf7d8fd [unknown] (/usr/lib/libglib-2.0.so.0.8000.2)
	    7528edf1af95 g_main_context_iteration+0x35 (/usr/lib/libglib-2.0.so.0.8000.2)
	    7528eda4ab86 g_application_run+0x1f6 (/usr/lib/libgio-2.0.so.0.8000.2)
	    7528ee6aa596 [unknown] (/usr/lib/libffi.so.8.1.4)
	    7fff24e862d8 [unknown] ([unknown])


         swapper       0 [000] 28178.463253:  195945410           cycles:P:  ffffffff91a1ae99 intel_idle+0x59 ([kernel.kallsyms])
     dbus-broker     412 [002] 28178.464855:  376737008           cycles:P:  ffffffff91c000a0 entry_SYSCALL_64+0x20 ([kernel.kallsyms])
```

Howard Chu (8):
  perf evsel: Set off-cpu BPF output to system-wide
  perf record --off-cpu: Add --off-cpu-thresh
  perf record --off-cpu: Parse offcpu-time event
  perf record off-cpu: Dump direct off-cpu samples in BPF
  perf record --off-cpu: Dump total off-cpu time at the end.
  perf evsel: Delete unnecessary = 0
  perf record --off-cpu: Parse BPF output embedded data
  perf test: Add direct off-cpu dumping test

 tools/perf/builtin-record.c             |  26 ++++
 tools/perf/builtin-script.c             |   4 +-
 tools/perf/tests/builtin-test.c         |   1 +
 tools/perf/tests/shell/record_offcpu.sh |  29 ++++
 tools/perf/tests/tests.h                |   1 +
 tools/perf/tests/workloads/Build        |   1 +
 tools/perf/tests/workloads/offcpu.c     |  16 +++
 tools/perf/util/bpf_off_cpu.c           | 174 +++++++++++++++---------
 tools/perf/util/bpf_skel/off_cpu.bpf.c  | 123 +++++++++++++++++
 tools/perf/util/evsel.c                 |  47 ++++---
 tools/perf/util/evsel.h                 |   6 +
 tools/perf/util/off_cpu.h               |  10 +-
 tools/perf/util/record.h                |   1 +
 tools/perf/util/session.c               |  12 +-
 14 files changed, 359 insertions(+), 92 deletions(-)
 create mode 100644 tools/perf/tests/workloads/offcpu.c

-- 
2.43.0