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 (9):
  perf evsel: Set 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 header: Add field 'embed'
  perf test: Add direct off-cpu dumping test

 tools/perf/builtin-record.c             |  26 ++++
 tools/perf/builtin-script.c             |   5 +-
 tools/perf/tests/builtin-test.c         |   1 +
 tools/perf/tests/shell/record_offcpu.sh |  27 ++++
 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           | 176 +++++++++++++++---------
 tools/perf/util/bpf_skel/off_cpu.bpf.c  | 135 ++++++++++++++++++
 tools/perf/util/evsel.c                 |  49 ++++---
 tools/perf/util/evsel.h                 |  13 ++
 tools/perf/util/header.c                |  12 ++
 tools/perf/util/off_cpu.h               |  10 +-
 tools/perf/util/record.h                |   1 +
 tools/perf/util/session.c               |  16 ++-
 15 files changed, 401 insertions(+), 88 deletions(-)
 create mode 100644 tools/perf/tests/workloads/offcpu.c

-- 
2.45.2

On Wed, Aug 7, 2024 at 8:38 AM Howard Chu <howardchu95@gmail.com> wrote:
>
> 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

Hi Howard,

I think this all looks good. There is an outstanding comment for patch
2/9 where a definition in a later patch needs moving to patch 2/9.
There is also a comment in 3/9 where you say you will turn a "=" back
to an "&=". These seem like small things to fix, could you rebase and
post the series? Are there other outstanding issues I'm missing? I'd
quite like to see this land.

Thanks,
Ian

> 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 (9):
>   perf evsel: Set 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 header: Add field 'embed'
>   perf test: Add direct off-cpu dumping test
>
>  tools/perf/builtin-record.c             |  26 ++++
>  tools/perf/builtin-script.c             |   5 +-
>  tools/perf/tests/builtin-test.c         |   1 +
>  tools/perf/tests/shell/record_offcpu.sh |  27 ++++
>  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           | 176 +++++++++++++++---------
>  tools/perf/util/bpf_skel/off_cpu.bpf.c  | 135 ++++++++++++++++++
>  tools/perf/util/evsel.c                 |  49 ++++---
>  tools/perf/util/evsel.h                 |  13 ++
>  tools/perf/util/header.c                |  12 ++
>  tools/perf/util/off_cpu.h               |  10 +-
>  tools/perf/util/record.h                |   1 +
>  tools/perf/util/session.c               |  16 ++-
>  15 files changed, 401 insertions(+), 88 deletions(-)
>  create mode 100644 tools/perf/tests/workloads/offcpu.c
>
> --
> 2.45.2
>

Hello Ian,

On Tue, Sep 24, 2024 at 8:04 PM Ian Rogers <irogers@google.com> wrote:
>
> On Wed, Aug 7, 2024 at 8:38 AM Howard Chu <howardchu95@gmail.com> wrote:
> >
> > 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
>
> Hi Howard,
>
> I think this all looks good. There is an outstanding comment for patch
> 2/9 where a definition in a later patch needs moving to patch 2/9.
> There is also a comment in 3/9 where you say you will turn a "=" back
> to an "&=". These seem like small things to fix, could you rebase and
> post the series? Are there other outstanding issues I'm missing? I'd

Thank you, I fixed them. Namhyung said the sample_embed thing should
be handled with care, so I'll make this sample_embed a special case
for off-cpu, and hard code something, so patches will look more
concise. Will do this,  rebase, and send the series. Sorry for taking
so long. (〒︿〒)

Thanks,
Howard
> quite like to see this land.
>
> Thanks,
> Ian
>
> > 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 (9):
> >   perf evsel: Set 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 header: Add field 'embed'
> >   perf test: Add direct off-cpu dumping test
> >
> >  tools/perf/builtin-record.c             |  26 ++++
> >  tools/perf/builtin-script.c             |   5 +-
> >  tools/perf/tests/builtin-test.c         |   1 +
> >  tools/perf/tests/shell/record_offcpu.sh |  27 ++++
> >  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           | 176 +++++++++++++++---------
> >  tools/perf/util/bpf_skel/off_cpu.bpf.c  | 135 ++++++++++++++++++
> >  tools/perf/util/evsel.c                 |  49 ++++---
> >  tools/perf/util/evsel.h                 |  13 ++
> >  tools/perf/util/header.c                |  12 ++
> >  tools/perf/util/off_cpu.h               |  10 +-
> >  tools/perf/util/record.h                |   1 +
> >  tools/perf/util/session.c               |  16 ++-
> >  15 files changed, 401 insertions(+), 88 deletions(-)
> >  create mode 100644 tools/perf/tests/workloads/offcpu.c
> >
> > --
> > 2.45.2
> >