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Message-ID: <CAP-5=fXsGB97D2CTeXhpiQCzUtbk8gd-GUrvw+um8Jx8tRU2=A@mail.gmail.com>
Date: Tue, 12 Nov 2024 10:59:59 -0800
From: Ian Rogers <irogers@...gle.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Howard Chu <howardchu95@...il.com>, peterz@...radead.org, namhyung@...nel.org,
mingo@...hat.com, mark.rutland@....com, james.clark@...aro.org,
alexander.shishkin@...ux.intel.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 v7 00/10] perf record --off-cpu: Dump off-cpu samples directly
On Tue, Nov 12, 2024 at 10:39 AM Arnaldo Carvalho de Melo
<acme@...nel.org> wrote:
>
> ⬢ [acme@...lbox perf-tools-next]$ git am ./v7_20241108_howardchu95_perf_record_off_cpu_dump_off_cpu_samples_directly.mbx
> Applying: perf record --off-cpu: Add --off-cpu-thresh option
> Applying: perf evsel: Expose evsel__is_offcpu_event() for future use
> Applying: perf record --off-cpu: Parse off-cpu event
> Applying: perf record --off-cpu: Preparation of off-cpu BPF program
> Applying: perf record --off-cpu: Dump off-cpu samples in BPF
> error: corrupt patch at line 107
> Patch failed at 0005 perf record --off-cpu: Dump off-cpu samples in BPF
> hint: Use 'git am --show-current-patch=diff' to see the failed patch
> hint: When you have resolved this problem, run "git am --continue".
> hint: If you prefer to skip this patch, run "git am --skip" instead.
> hint: To restore the original branch and stop patching, run "git am --abort".
> hint: Disable this message with "git config advice.mergeConflict false"
> ⬢ [acme@...lbox perf-tools-next]$
>
> This is on top of:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git tmp.perf-tools-next
>
> The message:
>
> error: corrupt patch at line 107
>
> Doesn't look like a clash with something that changed after you prepared
> this patch set.
>
> If we apply the first 4:
>
> ⬢ [acme@...lbox perf-tools-next]$ git am ./v7_20241108_howardchu95_perf_record_off_cpu_dump_off_cpu_samples_directly.mbx
> Applying: perf record --off-cpu: Add --off-cpu-thresh option
> Applying: perf evsel: Expose evsel__is_offcpu_event() for future use
> Applying: perf record --off-cpu: Parse off-cpu event
> Applying: perf record --off-cpu: Preparation of off-cpu BPF program
> ⬢ [acme@...lbox perf-tools-next]$
>
> Then try to apply just the 5th patch:
>
> ⬢ [acme@...lbox perf-tools-next]$ b4 am -P5 -ctsl --cc-trailers 20241108204137.2444151-2-howardchu95@...il.com
> ⬢ [acme@...lbox perf-tools-next]$ patch -p1 < ./v7_20241108_howardchu95_perf_record_off_cpu_dump_off_cpu_samples_directly.mbx
> patching file tools/perf/util/bpf_skel/off_cpu.bpf.c
> patch: **** malformed patch at line 138:
>
> ⬢ [acme@...lbox perf-tools-next]$
>
> You have:
>
> @@ -209,6 +268,12 @@ static int off_cpu_stat(u64 *ctx, struct task_struct *prev,
> pelem->state = state;
> pelem->stack_id = stack_id;
>
> + /*
> + * If stacks are successfully collected by bpf_get_stackid(), collect them once more
> + * in task_storage for direct off-cpu sample dumping
> + */
> + if (stack_id > 0 && bpf_get_stack(ctx, &pelem->stack, MAX_STACKS * sizeof(u64), BPF_F_USER_STACK)) {
> + }
> +
> next:
> pelem = bpf_task_storage_get(&tstamp, next, NULL, 0);
>
> @@ -223,11 +288,19 @@ static int off_cpu_stat(u64 *ctx, struct task_struct *prev,
>
> see the -209,6 +268,12? Did you edit it manually? It should be -209,6 +268,13
>
> And also what is the point of that empty if block?
There was some discussion of this already:
https://lore.kernel.org/lkml/CAP-5=fVXgQjAh1OFDN7DMp=xw5cAHRaO8j8UQfe4CZHrZc8uFg@mail.gmail.com/
TL;DR, it avoids an unused return value warning.
Thanks,
Ian
> - Arnaldo
>
> On Fri, Nov 08, 2024 at 12:41:27PM -0800, Howard Chu wrote:
> > 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 | 31 ++++++-
> > 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 | 115 ++++++++++++++----------
> > tools/perf/util/bpf_skel/off_cpu.bpf.c | 85 ++++++++++++++++--
> > 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, 264 insertions(+), 56 deletions(-)
> > create mode 100644 tools/perf/tests/workloads/offcpu.c
> >
> > --
> > 2.43.0
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