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perf record offcpu: Constify control data for BPF

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The control knobs set before loading BPF programs should be declared as
'const volatile' so that it can be optimized by the BPF core.

Committer testing:

  root@x1:~# perf record --off-cpu
  ^C[ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 1.807 MB perf.data (5645 samples) ]

  root@x1:~# perf evlist
  cpu_atom/cycles/P
  cpu_core/cycles/P
  offcpu-time
  dummy:u
  root@x1:~# perf evlist -v
  cpu_atom/cycles/P: type: 0 (PERF_TYPE_HARDWARE), size: 136, config: 0xa00000000, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|CPU|PERIOD|IDENTIFIER, read_format: ID|LOST, disabled: 1, inherit: 1, freq: 1, precise_ip: 3, sample_id_all: 1
  cpu_core/cycles/P: type: 0 (PERF_TYPE_HARDWARE), size: 136, config: 0x400000000, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|CPU|PERIOD|IDENTIFIER, read_format: ID|LOST, disabled: 1, inherit: 1, freq: 1, precise_ip: 3, sample_id_all: 1
  offcpu-time: type: 1 (software), size: 136, config: 0xa (PERF_COUNT_SW_BPF_OUTPUT), { sample_period, sample_freq }: 1, sample_type: IP|TID|TIME|CALLCHAIN|CPU|PERIOD|IDENTIFIER, read_format: ID|LOST, disabled: 1, inherit: 1, freq: 1, sample_id_all: 1
  dummy:u: type: 1 (software), size: 136, config: 0x9 (PERF_COUNT_SW_DUMMY), { sample_period, sample_freq }: 1, sample_type: IP|TID|TIME|CPU|IDENTIFIER, read_format: ID|LOST, inherit: 1, exclude_kernel: 1, exclude_hv: 1, mmap: 1, comm: 1, task: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1
  root@x1:~# perf trace -e bpf --max-events 5 perf record --off-cpu
       0.000 ( 0.015 ms): :2949124/2949124 bpf(cmd: 36, uattr: 0x7ffefc6dbe30, size: 8)          = -1 EOPNOTSUPP (Operation not supported)
       0.031 ( 0.115 ms): :2949124/2949124 bpf(cmd: PROG_LOAD, uattr: 0x7ffefc6dbb60, size: 148) = 14
       0.159 ( 0.037 ms): :2949124/2949124 bpf(cmd: PROG_LOAD, uattr: 0x7ffefc6dbc20, size: 148) = 14
      23.868 ( 0.144 ms): perf/2949124 bpf(cmd: PROG_LOAD, uattr: 0x7ffefc6dbad0, size: 148)     = 14
      24.027 ( 0.014 ms): perf/2949124 bpf(uattr: 0x7ffefc6dbc80, size: 80)                      = 14
  root@x1:~#

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240902200515.2103769-6-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Namhyung Kim 2024-09-02 13:05:15 -07:00 committed by Arnaldo Carvalho de Melo
parent 4afdc00c37
commit 8b3b1bb3ea
2 changed files with 13 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
tools/perf/util/bpf_off_cpu.c
View File

@ -73,14 +73,12 @@ static void off_cpu_start(void *arg)
struct evlist *evlist = arg;
/* update task filter for the given workload */
if (!skel->bss->has_cpu && !skel->bss->has_task &&
if (skel->rodata->has_task && skel->rodata->uses_tgid &&
perf_thread_map__pid(evlist->core.threads, 0) != -1) {
int fd;
u32 pid;
u8 val = 1;
skel->bss->has_task = 1;
skel->bss->uses_tgid = 1;
fd = bpf_map__fd(skel->maps.task_filter);
pid = perf_thread_map__pid(evlist->core.threads, 0);
bpf_map_update_elem(fd, &pid, &val, BPF_ANY);
@ -148,6 +146,7 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
if (target->cpu_list) {
ncpus = perf_cpu_map__nr(evlist->core.user_requested_cpus);
bpf_map__set_max_entries(skel->maps.cpu_filter, ncpus);
skel->rodata->has_cpu = 1;
}
if (target->pid) {
@ -173,11 +172,16 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
ntasks = MAX_PROC;
bpf_map__set_max_entries(skel->maps.task_filter, ntasks);
skel->rodata->has_task = 1;
skel->rodata->uses_tgid = 1;
} else if (target__has_task(target)) {
ntasks = perf_thread_map__nr(evlist->core.threads);
bpf_map__set_max_entries(skel->maps.task_filter, ntasks);
skel->rodata->has_task = 1;
} else if (target__none(target)) {
bpf_map__set_max_entries(skel->maps.task_filter, MAX_PROC);
skel->rodata->has_task = 1;
skel->rodata->uses_tgid = 1;
}
if (evlist__first(evlist)->cgrp) {
@ -186,6 +190,7 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
if (!cgroup_is_v2("perf_event"))
skel->rodata->uses_cgroup_v1 = true;
skel->rodata->has_cgroup = 1;
}
if (opts->record_cgroup) {
@ -208,7 +213,6 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
u32 cpu;
u8 val = 1;
skel->bss->has_cpu = 1;
fd = bpf_map__fd(skel->maps.cpu_filter);
for (i = 0; i < ncpus; i++) {
@ -220,8 +224,6 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
if (target->pid) {
u8 val = 1;
skel->bss->has_task = 1;
skel->bss->uses_tgid = 1;
fd = bpf_map__fd(skel->maps.task_filter);
strlist__for_each_entry(pos, pid_slist) {
@ -240,7 +242,6 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
u32 pid;
u8 val = 1;
skel->bss->has_task = 1;
fd = bpf_map__fd(skel->maps.task_filter);
for (i = 0; i < ntasks; i++) {
@ -253,7 +254,6 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
struct evsel *evsel;
u8 val = 1;
skel->bss->has_cgroup = 1;
fd = bpf_map__fd(skel->maps.cgroup_filter);
evlist__for_each_entry(evlist, evsel) {

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

@ -85,10 +85,11 @@ struct task_struct___old {
} __attribute__((preserve_access_index));
int enabled = 0;
int has_cpu = 0;
int has_task = 0;
int has_cgroup = 0;
int uses_tgid = 0;
const volatile int has_cpu = 0;
const volatile int has_task = 0;
const volatile int has_cgroup = 0;
const volatile int uses_tgid = 0;
const volatile bool has_prev_state = false;
const volatile bool needs_cgroup = false;