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perf record --off-cpu: Preparation of off-cpu BPF program

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Set the perf_event map in BPF for dumping off-cpu samples, and set the
offcpu_thresh to specify the threshold.

Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Howard Chu <howardchu95@gmail.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Gautam Menghani <gautam@linux.ibm.com>
Tested-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241108204137.2444151-5-howardchu95@gmail.com
Link: https://lore.kernel.org/r/20250501022809.449767-4-howardchu95@gmail.com
[ Added some missing iteration variables to off_cpu_config() and fixed up
  a manually edited patch hunk line boundary line ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Howard Chu 2025-04-30 19:28:01 -07:00 committed by Arnaldo Carvalho de Melo
parent 0f72027bb9
commit 282c195906
2 changed files with 33 additions and 0 deletions
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24
tools/perf/util/bpf_off_cpu.c
View File

@ -13,6 +13,7 @@
#include "util/cgroup.h"
#include "util/strlist.h"
#include <bpf/bpf.h>
#include <internal/xyarray.h>
#include "bpf_skel/off_cpu.skel.h"
@ -60,6 +61,9 @@ static int off_cpu_config(struct evlist *evlist)
static void off_cpu_start(void *arg)
{
struct evlist *evlist = arg;
struct evsel *evsel;
struct perf_cpu pcpu;
int i;
/* update task filter for the given workload */
if (skel->rodata->has_task && skel->rodata->uses_tgid &&
@ -73,6 +77,26 @@ static void off_cpu_start(void *arg)
bpf_map_update_elem(fd, &pid, &val, BPF_ANY);
}
/* update BPF perf_event map */
evsel = evlist__find_evsel_by_str(evlist, OFFCPU_EVENT);
if (evsel == NULL) {
pr_err("%s evsel not found\n", OFFCPU_EVENT);
return;
}
perf_cpu_map__for_each_cpu(pcpu, i, evsel->core.cpus) {
int err;
int cpu_nr = pcpu.cpu;
err = bpf_map__update_elem(skel->maps.offcpu_output, &cpu_nr, sizeof(int),
xyarray__entry(evsel->core.fd, cpu_nr, 0),
sizeof(int), BPF_ANY);
if (err) {
pr_err("Failed to update perf event map for direct off-cpu dumping\n");
return;
}
}
skel->bss->enabled = 1;
}

9
tools/perf/util/bpf_skel/off_cpu.bpf.c
View File

@ -18,6 +18,8 @@
#define MAX_STACKS 32
#define MAX_ENTRIES 102400
#define MAX_CPUS 4096
struct tstamp_data {
__u32 stack_id;
__u32 state;
@ -39,6 +41,13 @@ struct {
__uint(max_entries, MAX_ENTRIES);
} stacks SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
__uint(key_size, sizeof(int));
__uint(value_size, sizeof(int));
__uint(max_entries, MAX_CPUS);
} offcpu_output SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
__uint(map_flags, BPF_F_NO_PREALLOC);