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Message-Id: <20220624231313.367909-6-namhyung@kernel.org>
Date: Fri, 24 Jun 2022 16:13:12 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
Jiri Olsa <jolsa@...nel.org>
Cc: Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
LKML <linux-kernel@...r.kernel.org>,
Ian Rogers <irogers@...gle.com>,
linux-perf-users@...r.kernel.org, Song Liu <songliubraving@...com>,
Hao Luo <haoluo@...gle.com>,
Milian Wolff <milian.wolff@...b.com>, bpf@...r.kernel.org,
Blake Jones <blakejones@...gle.com>
Subject: [PATCH 5/6] perf offcpu: Track child processes
When -p option used or a workload is given, it needs to handle child
processes. The perf_event can inherit those task events
automatically. We can add a new BPF program in task_newtask
tracepoint to track child processes.
Before:
$ sudo perf record --off-cpu -- perf bench sched messaging
$ sudo perf report --stat | grep -A1 offcpu
offcpu-time stats:
SAMPLE events: 1
After:
$ sudo perf record -a --off-cpu -- perf bench sched messaging
$ sudo perf report --stat | grep -A1 offcpu
offcpu-time stats:
SAMPLE events: 856
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
tools/perf/util/bpf_off_cpu.c | 7 ++++++
tools/perf/util/bpf_skel/off_cpu.bpf.c | 30 ++++++++++++++++++++++++++
2 files changed, 37 insertions(+)
diff --git a/tools/perf/util/bpf_off_cpu.c b/tools/perf/util/bpf_off_cpu.c
index f7ee0c7a53f0..c257813e674e 100644
--- a/tools/perf/util/bpf_off_cpu.c
+++ b/tools/perf/util/bpf_off_cpu.c
@@ -17,6 +17,7 @@
#include "bpf_skel/off_cpu.skel.h"
#define MAX_STACKS 32
+#define MAX_PROC 4096
/* we don't need actual timestamp, just want to put the samples at last */
#define OFF_CPU_TIMESTAMP (~0ull << 32)
@@ -164,10 +165,16 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
ntasks++;
}
+
+ if (ntasks < MAX_PROC)
+ ntasks = MAX_PROC;
+
bpf_map__set_max_entries(skel->maps.task_filter, ntasks);
} else if (target__has_task(target)) {
ntasks = perf_thread_map__nr(evlist->core.threads);
bpf_map__set_max_entries(skel->maps.task_filter, ntasks);
+ } else if (target__none(target)) {
+ bpf_map__set_max_entries(skel->maps.task_filter, MAX_PROC);
}
if (evlist__first(evlist)->cgrp) {
diff --git a/tools/perf/util/bpf_skel/off_cpu.bpf.c b/tools/perf/util/bpf_skel/off_cpu.bpf.c
index 143a8b7acf87..c4ba2bcf179f 100644
--- a/tools/perf/util/bpf_skel/off_cpu.bpf.c
+++ b/tools/perf/util/bpf_skel/off_cpu.bpf.c
@@ -12,6 +12,9 @@
#define TASK_INTERRUPTIBLE 0x0001
#define TASK_UNINTERRUPTIBLE 0x0002
+/* create a new thread */
+#define CLONE_THREAD 0x10000
+
#define MAX_STACKS 32
#define MAX_ENTRIES 102400
@@ -220,6 +223,33 @@ static int off_cpu_stat(u64 *ctx, struct task_struct *prev,
return 0;
}
+SEC("tp_btf/task_newtask")
+int on_newtask(u64 *ctx)
+{
+ struct task_struct *task;
+ u64 clone_flags;
+ u32 pid;
+ u8 val = 1;
+
+ if (!uses_tgid)
+ return 0;
+
+ task = (struct task_struct *)bpf_get_current_task();
+
+ pid = BPF_CORE_READ(task, tgid);
+ if (!bpf_map_lookup_elem(&task_filter, &pid))
+ return 0;
+
+ task = (struct task_struct *)ctx[0];
+ clone_flags = ctx[1];
+
+ pid = task->tgid;
+ if (!(clone_flags & CLONE_THREAD))
+ bpf_map_update_elem(&task_filter, &pid, &val, BPF_NOEXIST);
+
+ return 0;
+}
+
SEC("tp_btf/sched_switch")
int on_switch(u64 *ctx)
{
--
2.37.0.rc0.161.g10f37bed90-goog
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