tools/perf/Documentation/perf-record.txt | 9 ++ tools/perf/builtin-record.c | 33 +++++++ tools/perf/builtin-script.c | 4 +- tools/perf/tests/shell/record_offcpu.sh | 71 ++++++++++++++ tools/perf/util/bpf_off_cpu.c | 119 ++++++++++++++--------- tools/perf/util/bpf_skel/off_cpu.bpf.c | 98 ++++++++++++++++++- tools/perf/util/evsel.c | 41 +++++++- tools/perf/util/evsel.h | 2 + tools/perf/util/off_cpu.h | 3 +- tools/perf/util/record.h | 1 + 10 files changed, 324 insertions(+), 57 deletions(-)
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])
```
Changes in v16:
- Add Tested-by from Gautam and Acked-by from Namhyung.
- Rebase on the perf-tools-next branch.
- Edit the commit message of patch 10.
- Fix a bug caused by the type change of struct perf_cpu.
- Rename test_offcpu_over_thresh() to test_offcpu_above_thresh().
Changes in v15:
- Fix workload recording bug pointed out by Arnaldo.
- Rename struct stack to struct __stack as suggested by Arnaldo.
- Delete the extra offcpu workload now that recording workload is fixed,
use 'sleep 1' for testing instead.
- Add more tests for the off-cpu-thresh option.
Changes in v14:
- Change the internal off_cpu_thresh_us to off_cpu_thresh_ns, i.e. use
nsec instead of usec
Changes in v13:
- Move the definition of 'off_cpu_thresh_ns' to the same commit as
dumping off-cpu samples in BPF, and give off_cpu_thresh_ns a default
value before the --off-cpu-thresh option is parsed.
Changes in v12:
- Restore patches' bisectability, because the ordering of patches has
changed.
- Change 'us = ms * 1000' to 'us = ms * USEC_PER_MSEC'
Changes in v11:
- Modify the options used in the off-cpu tests, as I changed the unit
of the off-cpu threshold to milliseconds.
Changes in v10:
- Move the commit "perf record --off-cpu: Add --off-cpu-thresh option"
to where the direct sample feature is completed.
- Make --off-cpu-thresh use milliseconds as the unit.
Changes in v9:
- Add documentation for the new option '--off-cpu-thresh', and include
an example of its usage in the commit message
- Set inherit in evsel__config() to prevent future modifications
- Support off-cpu sample data collected by perf before this patch series
Changes in v8:
- Make this series bisectable
- Rename off_cpu_thresh to off_cpu_thresh_us and offcpu_thresh (in BPF)
to offcpu_thresh_ns for clarity
- Add commit messages to 'perf evsel: Expose evsel__is_offcpu_event()
for future use' commit
- Correct spelling mistakes in the commit message (s/is should be/should be/)
- Add kernel-doc comments to off_cpu_dump(), and comments to the empty
if block
- Add some comments to off-cpu test
- Delete an unused variable 'timestamp' in off_cpu_dump()
Changes in v7:
- Make off-cpu event system-wide
- Use strtoull instead of strtoul
- Delete unused variable such as sample_id, and sample_type
- Use i as index to update BPF perf_event map
- MAX_OFFCPU_LEN 128 is too big, make it smaller.
- Delete some bound check as it's always guaranteed
- Do not set ip_pos in BPF
- Add a new field for storing stack traces in the tstamp map
- Dump the off-cpu sample directly or save it in the off_cpu map, not both
- Delete the sample_type_off_cpu check
- Use __set_off_cpu_sample() to parse samples instead of a two-pass parsing
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
Howard Chu (10):
perf evsel: Expose evsel__is_offcpu_event() for future use
perf record --off-cpu: Parse off-cpu event
perf record --off-cpu: Preparation of off-cpu BPF program
perf record --off-cpu: Dump off-cpu samples in BPF
perf evsel: Assemble offcpu samples
perf record --off-cpu: Disable perf_event's callchain collection
perf script: Display off-cpu samples correctly
perf record --off-cpu: Dump the remaining samples in BPF's stack trace
map
perf record --off-cpu: Add --off-cpu-thresh option
perf test: Add direct off-cpu tests
tools/perf/Documentation/perf-record.txt | 9 ++
tools/perf/builtin-record.c | 33 +++++++
tools/perf/builtin-script.c | 4 +-
tools/perf/tests/shell/record_offcpu.sh | 71 ++++++++++++++
tools/perf/util/bpf_off_cpu.c | 119 ++++++++++++++---------
tools/perf/util/bpf_skel/off_cpu.bpf.c | 98 ++++++++++++++++++-
tools/perf/util/evsel.c | 41 +++++++-
tools/perf/util/evsel.h | 2 +
tools/perf/util/off_cpu.h | 3 +-
tools/perf/util/record.h | 1 +
10 files changed, 324 insertions(+), 57 deletions(-)
--
2.45.2
On Wed, Apr 30, 2025 at 07:27:58PM -0700, Howard Chu wrote: > Changes in v16: > - Add Tested-by from Gautam and Acked-by from Namhyung. > - Rebase on the perf-tools-next branch. > - Edit the commit message of patch 10. > - Fix a bug caused by the type change of struct perf_cpu. > - Rename test_offcpu_over_thresh() to test_offcpu_above_thresh(). Please take a look at the tmp.perf-tools-next branch at: https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git I added some Committer testing with some extra steps to describe how to reproduce the results and there is one point that I have to retest, where there is a FIXME in the Committer testing notes, perhaps I made a mistake or that fix should be moved to after or before some patch, unsure. - Arnaldo
On Mon, May 5, 2025 at 8:56 AM Arnaldo Carvalho de Melo <acme@kernel.org> wrote:
>
> On Wed, Apr 30, 2025 at 07:27:58PM -0700, Howard Chu wrote:
> > Changes in v16:
> > - Add Tested-by from Gautam and Acked-by from Namhyung.
> > - Rebase on the perf-tools-next branch.
> > - Edit the commit message of patch 10.
> > - Fix a bug caused by the type change of struct perf_cpu.
> > - Rename test_offcpu_over_thresh() to test_offcpu_above_thresh().
>
> Please take a look at the tmp.perf-tools-next branch at:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git
>
> I added some Committer testing with some extra steps to describe how to
> reproduce the results and there is one point that I have to retest,
> where there is a FIXME in the Committer testing notes, perhaps I made a
> mistake or that fix should be moved to after or before some patch,
> unsure.
Hi Arnaldo,
so I tried out the tree, perf tests pass as usual, etc. I tried to dig
into your FIXME issue. Initially I thought I had a reproduction but
now I think it was a user error. So I wrote a little script where
we're setting the off CPU threshold to 10 seconds and then looking for
off CPU events that took less than than:
```
for i in $(seq 1 100)
do
echo -n "Iteration $i of 100 "
sudo /tmp/perf/perf record --off-cpu --off-cpu-thresh 10000 -a sleep
11 2> /dev/null
if sudo /tmp/perf/perf script -D |grep -P '.* [0-9]{1,10} offcpu.*'
then
echo "BAD"
else
echo "GOOD"
fi
done
```
To remove the BPF map generated events I added:
```
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 8898357325cf..6c23b2cf8b66 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -2841,7 +2841,7 @@ static int __cmd_record(struct record *rec, int
argc, const char **argv)
} else
status = err;
- if (rec->off_cpu)
+ if (rec->off_cpu && false)
rec->bytes_written += off_cpu_write(rec->session);
record__read_lost_samples(rec);
```
Anyway, running the script for nearly 20 minutes, I couldn't get a
sample below the threshold. Hand testing things also look correct.
Thanks,
Ian
On Wed, Apr 30, 2025 at 7:28 PM Howard Chu <howardchu95@gmail.com> wrote: > > 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]) > ``` Tested-by: Ian Rogers <irogers@google.com> and in the process coming across: https://lore.kernel.org/lkml/20250501070003.22251-1-irogers@google.com/ Thanks for persisting with this, we're past the 1 year milestone: https://lore.kernel.org/linux-perf-users/20240424024805.144759-1-howardchu95@gmail.com/ Thanks! Ian > Changes in v16: > - Add Tested-by from Gautam and Acked-by from Namhyung. > - Rebase on the perf-tools-next branch. > - Edit the commit message of patch 10. > - Fix a bug caused by the type change of struct perf_cpu. > - Rename test_offcpu_over_thresh() to test_offcpu_above_thresh(). > > Changes in v15: > - Fix workload recording bug pointed out by Arnaldo. > - Rename struct stack to struct __stack as suggested by Arnaldo. > - Delete the extra offcpu workload now that recording workload is fixed, > use 'sleep 1' for testing instead. > - Add more tests for the off-cpu-thresh option. > > Changes in v14: > - Change the internal off_cpu_thresh_us to off_cpu_thresh_ns, i.e. use > nsec instead of usec > > Changes in v13: > - Move the definition of 'off_cpu_thresh_ns' to the same commit as > dumping off-cpu samples in BPF, and give off_cpu_thresh_ns a default > value before the --off-cpu-thresh option is parsed. > > Changes in v12: > - Restore patches' bisectability, because the ordering of patches has > changed. > - Change 'us = ms * 1000' to 'us = ms * USEC_PER_MSEC' > > Changes in v11: > - Modify the options used in the off-cpu tests, as I changed the unit > of the off-cpu threshold to milliseconds. > > Changes in v10: > - Move the commit "perf record --off-cpu: Add --off-cpu-thresh option" > to where the direct sample feature is completed. > - Make --off-cpu-thresh use milliseconds as the unit. > > Changes in v9: > - Add documentation for the new option '--off-cpu-thresh', and include > an example of its usage in the commit message > - Set inherit in evsel__config() to prevent future modifications > - Support off-cpu sample data collected by perf before this patch series > > Changes in v8: > - Make this series bisectable > - Rename off_cpu_thresh to off_cpu_thresh_us and offcpu_thresh (in BPF) > to offcpu_thresh_ns for clarity > - Add commit messages to 'perf evsel: Expose evsel__is_offcpu_event() > for future use' commit > - Correct spelling mistakes in the commit message (s/is should be/should be/) > - Add kernel-doc comments to off_cpu_dump(), and comments to the empty > if block > - Add some comments to off-cpu test > - Delete an unused variable 'timestamp' in off_cpu_dump() > > Changes in v7: > - Make off-cpu event system-wide > - Use strtoull instead of strtoul > - Delete unused variable such as sample_id, and sample_type > - Use i as index to update BPF perf_event map > - MAX_OFFCPU_LEN 128 is too big, make it smaller. > - Delete some bound check as it's always guaranteed > - Do not set ip_pos in BPF > - Add a new field for storing stack traces in the tstamp map > - Dump the off-cpu sample directly or save it in the off_cpu map, not both > - Delete the sample_type_off_cpu check > - Use __set_off_cpu_sample() to parse samples instead of a two-pass parsing > > 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 > > Howard Chu (10): > perf evsel: Expose evsel__is_offcpu_event() for future use > perf record --off-cpu: Parse off-cpu event > perf record --off-cpu: Preparation of off-cpu BPF program > perf record --off-cpu: Dump off-cpu samples in BPF > perf evsel: Assemble offcpu samples > perf record --off-cpu: Disable perf_event's callchain collection > perf script: Display off-cpu samples correctly > perf record --off-cpu: Dump the remaining samples in BPF's stack trace > map > perf record --off-cpu: Add --off-cpu-thresh option > perf test: Add direct off-cpu tests > > tools/perf/Documentation/perf-record.txt | 9 ++ > tools/perf/builtin-record.c | 33 +++++++ > tools/perf/builtin-script.c | 4 +- > tools/perf/tests/shell/record_offcpu.sh | 71 ++++++++++++++ > tools/perf/util/bpf_off_cpu.c | 119 ++++++++++++++--------- > tools/perf/util/bpf_skel/off_cpu.bpf.c | 98 ++++++++++++++++++- > tools/perf/util/evsel.c | 41 +++++++- > tools/perf/util/evsel.h | 2 + > tools/perf/util/off_cpu.h | 3 +- > tools/perf/util/record.h | 1 + > 10 files changed, 324 insertions(+), 57 deletions(-) > > -- > 2.45.2 >
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