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Message-ID: <ZvcCDkrzwilKYQR2@x1>
Date: Fri, 27 Sep 2024 16:05:50 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Howard Chu <howardchu95@...il.com>
Cc: peterz@...radead.org, mingo@...hat.com, namhyung@...nel.org,
mark.rutland@....com, alexander.shishkin@...ux.intel.com,
jolsa@...nel.org, irogers@...gle.com, adrian.hunter@...el.com,
kan.liang@...ux.intel.com, linux-perf-users@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 0/8] perf record --off-cpu: Dump off-cpu samples
directly
On Fri, Sep 27, 2024 at 11:53:32AM -0700, Howard Chu wrote:
> 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
Thanks, I'll try to review and test this early next week, and check on
bisectability issues as you mentioned privately.
Thanks!
- Arnaldo
> 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
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