From d23477637ac6d29f946461a2fa5eb616cfa5d3f0 Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Thu, 11 Aug 2022 11:54:55 -0700 Subject: [PATCH] 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 Cc: Blake Jones Cc: Hao Luo Cc: Ian Rogers Cc: Ingo Molnar Cc: Jiri Olsa Cc: Milian Wolff Cc: Peter Zijlstra Cc: Song Liu Cc: bpf@vger.kernel.org Link: https://lore.kernel.org/r/20220811185456.194721-4-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- 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 f7ee0c7..c257813 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 143a8b7..c4ba2bc 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 @@ next: 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) { -- 2.7.4