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Message-ID: <Zi_slOlsZBjTbNIH@x1>
Date: Mon, 29 Apr 2024 15:53:08 -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, zegao2021@...il.com, leo.yan@...ux.dev,
ravi.bangoria@....com, linux-perf-users@...r.kernel.org,
linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH v1 1/4] perf record: Dump off-cpu samples directly
On Mon, Apr 22, 2024 at 04:36:45PM +0800, Howard Chu wrote:
> Parse off-cpu events using parse_event(). Change the placement of
> record__config_off_cpu to after record__open because we need to write
> mmapped fds into BPF's perf_event_array map, also, write
> sample_id/sample_type into BPF. In record__pushfn and record__aio_pushfn,
> handle off-cpu samples using off_cpu_strip. This is because the off-cpu
> samples that we want to write to perf.data is in off-cpu samples' raw_data
> section:
Hey,
This lacks a cover letter and the chainig of patches so that b4
can fetch the series.
Also all 5 patches have the same summary and different
descriptions and contents, can you please rework the patch series, using
'git format-patch', and make the description reflect what each patch is
doing?
Thanks,
- Arnaldo
> regular samples:
> [sample: sample_data]
>
> off-cpu samples:
> [sample: [raw_data: sample_data]]
>
> We need to extract the real useful sample data out before writing.
>
> Hooks record_done just before evlist__disable to stop BPF program from
> outputting, otherwise, we lose some samples.
>
> After samples are collected, change sample_type of off-cpu event to
> the OFFCPU_SAMPLE_TYPES for parsing correctly, it was PERF_SAMPLE_RAW and
> some others, because BPF can only output to a specific type of perf_event,
> which is why `evsel->core.attr.sample_type &= OFFCPU_SAMPLE_TYPES;` is
> deleted in util/evsel.c.
>
> Signed-off-by: Howard Chu <howardchu95@...il.com>
> ---
> tools/perf/builtin-record.c | 98 ++++++++++++++++++++++++++++++++++---
> tools/perf/util/evsel.c | 8 ---
> 2 files changed, 91 insertions(+), 15 deletions(-)
>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 2ff718d3e202..c31b23905f1b 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -389,6 +389,8 @@ struct record_aio {
> static int record__aio_pushfn(struct mmap *map, void *to, void *buf, size_t size)
> {
> struct record_aio *aio = to;
> + char *bf_stripped = NULL;
> + size_t stripped;
>
> /*
> * map->core.base data pointed by buf is copied into free map->aio.data[] buffer
> @@ -404,6 +406,31 @@ static int record__aio_pushfn(struct mmap *map, void *to, void *buf, size_t size
> * from the beginning of the kernel buffer till the end of the data chunk.
> */
>
> + if (aio->rec->off_cpu) {
> + if (size == 0)
> + return 0;
> +
> + map->core.start -= size;
> + size = map->core.end - map->core.start;
> +
> + bf_stripped = malloc(size);
> +
> + if (bf_stripped == NULL) {
> + pr_err("Failed to allocate off-cpu strip buffer\n");
> + return -ENOMEM;
> + }
> +
> + stripped = off_cpu_strip(aio->rec->evlist, map, bf_stripped, size);
> +
> + if (stripped < 0) {
> + size = (int)stripped;
> + goto out;
> + }
> +
> + size = stripped;
> + buf = bf_stripped;
> + }
> +
> if (record__comp_enabled(aio->rec)) {
> ssize_t compressed = zstd_compress(aio->rec->session, NULL, aio->data + aio->size,
> mmap__mmap_len(map) - aio->size,
> @@ -432,6 +459,9 @@ static int record__aio_pushfn(struct mmap *map, void *to, void *buf, size_t size
>
> aio->size += size;
>
> +out:
> + free(bf_stripped);
> +
> return size;
> }
>
> @@ -635,6 +665,38 @@ static int process_locked_synthesized_event(struct perf_tool *tool,
> static int record__pushfn(struct mmap *map, void *to, void *bf, size_t size)
> {
> struct record *rec = to;
> + int err;
> + char *bf_stripped = NULL;
> + size_t stripped;
> +
> + if (rec->off_cpu) {
> + /*
> + * We'll read all the events at once without masking.
> + * When reading the remainder from a map, the size is 0, because
> + * start is shifted to the end so no more data is to be read.
> + */
> + if (size == 0)
> + return 0;
> +
> + map->core.start -= size;
> + /* get the total size */
> + size = map->core.end - map->core.start;
> +
> + bf_stripped = malloc(size);
> +
> + if (bf_stripped == NULL) {
> + pr_err("Failed to allocate off-cpu strip buffer\n");
> + return -ENOMEM;
> + }
> +
> + stripped = off_cpu_strip(rec->evlist, map, bf_stripped, size);
> +
> + if (stripped < 0)
> + return (int)stripped;
> +
> + size = stripped;
> + bf = bf_stripped;
> + }
>
> if (record__comp_enabled(rec)) {
> ssize_t compressed = zstd_compress(rec->session, map, map->data,
> @@ -648,7 +710,11 @@ static int record__pushfn(struct mmap *map, void *to, void *bf, size_t size)
> }
>
> thread->samples++;
> - return record__write(rec, map, bf, size);
> + err = record__write(rec, map, bf, size);
> +
> + free(bf_stripped);
> +
> + return err;
> }
>
> static volatile sig_atomic_t signr = -1;
> @@ -1790,6 +1856,7 @@ record__finish_output(struct record *rec)
> if (rec->buildid_all)
> perf_session__dsos_hit_all(rec->session);
> }
> +
> perf_session__write_header(rec->session, rec->evlist, fd, true);
>
> return;
> @@ -2501,6 +2568,14 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
> }
> }
>
> + if (rec->off_cpu) {
> + err = record__config_off_cpu(rec);
> + if (err) {
> + pr_err("record__config_off_cpu failed, error %d\n", err);
> + goto out_free_threads;
> + }
> + }
> +
> /*
> * Normally perf_session__new would do this, but it doesn't have the
> * evlist.
> @@ -2764,6 +2839,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
> * disable events in this case.
> */
> if (done && !disabled && !target__none(&opts->target)) {
> + perf_hooks__invoke_record_done();
> trigger_off(&auxtrace_snapshot_trigger);
> evlist__disable(rec->evlist);
> disabled = true;
> @@ -2827,14 +2903,17 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
> } else
> status = err;
>
> - if (rec->off_cpu)
> - rec->bytes_written += off_cpu_write(rec->session);
> -
> record__read_lost_samples(rec);
> record__synthesize(rec, true);
> /* this will be recalculated during process_buildids() */
> rec->samples = 0;
>
> + /* change to the correct sample type for parsing */
> + if (rec->off_cpu && off_cpu_change_type(rec->evlist)) {
> + pr_err("ERROR: Failed to change sample type for off-cpu event\n");
> + goto out_delete_session;
> + }
> +
> if (!err) {
> if (!rec->timestamp_filename) {
> record__finish_output(rec);
> @@ -3198,7 +3277,7 @@ static int switch_output_setup(struct record *rec)
> unsigned long val;
>
> /*
> - * If we're using --switch-output-events, then we imply its
> + * If we're using --switch-output-events, then we imply its
> * --switch-output=signal, as we'll send a SIGUSR2 from the side band
> * thread to its parent.
> */
> @@ -4221,9 +4300,14 @@ int cmd_record(int argc, const char **argv)
> }
>
> if (rec->off_cpu) {
> - err = record__config_off_cpu(rec);
> + char off_cpu_event[64];
> +
> + snprintf(off_cpu_event, sizeof(off_cpu_event),
> + "bpf-output/no-inherit=1,name=%s/", OFFCPU_EVENT);
> +
> + err = parse_event(rec->evlist, off_cpu_event);
> if (err) {
> - pr_err("record__config_off_cpu failed, error %d\n", err);
> + pr_err("Failed to open off-cpu event\n");
> goto out;
> }
> }
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 3536404e9447..c08ae6a3c8d6 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -1092,11 +1092,6 @@ static void evsel__set_default_freq_period(struct record_opts *opts,
> }
> }
>
> -static bool evsel__is_offcpu_event(struct evsel *evsel)
> -{
> - return evsel__is_bpf_output(evsel) && evsel__name_is(evsel, OFFCPU_EVENT);
> -}
> -
> /*
> * The enable_on_exec/disabled value strategy:
> *
> @@ -1363,9 +1358,6 @@ void evsel__config(struct evsel *evsel, struct record_opts *opts,
> if (evsel__is_dummy_event(evsel))
> evsel__reset_sample_bit(evsel, BRANCH_STACK);
>
> - if (evsel__is_offcpu_event(evsel))
> - evsel->core.attr.sample_type &= OFFCPU_SAMPLE_TYPES;
> -
> arch__post_evsel_config(evsel, attr);
> }
>
> --
> 2.44.0
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