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Message-ID: <CAP-5=fXCxSKgbe141mgo--taFa=-L=Oe9o7hHrjC4rj-eAP57w@mail.gmail.com> Date: Wed, 13 Nov 2024 09:08:25 -0800 From: Ian Rogers <irogers@...gle.com> To: Howard Chu <howardchu95@...il.com> Cc: acme@...nel.org, peterz@...radead.org, namhyung@...nel.org, mingo@...hat.com, jolsa@...nel.org, adrian.hunter@...el.com, kan.liang@...ux.intel.com, linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v8 00/10] perf record --off-cpu: Dump off-cpu samples directly On Tue, Nov 12, 2024 at 4:28 PM Howard Chu <howardchu95@...il.com> wrote: > > 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() I spotted a few issues in v7, but v8 looks good to me. Reviewed-by: Ian Rogers <irogers@...gle.com> Thanks, Ian > 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 > > 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 (10): > perf record --off-cpu: Add --off-cpu-thresh option > 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 test: Add direct off-cpu 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 | 35 ++++++- > 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 | 117 ++++++++++++++---------- > tools/perf/util/bpf_skel/off_cpu.bpf.c | 97 +++++++++++++++++++- > tools/perf/util/evsel.c | 34 ++++++- > tools/perf/util/evsel.h | 2 + > tools/perf/util/off_cpu.h | 3 +- > tools/perf/util/record.h | 1 + > 13 files changed, 282 insertions(+), 56 deletions(-) > create mode 100644 tools/perf/tests/workloads/offcpu.c > > -- > 2.43.0 >
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