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authorSong Liu <songliubraving@fb.com>2018-03-12 09:59:43 -0700
committerIngo Molnar <mingo@kernel.org>2018-03-20 08:58:47 +0100
commitc917e0f259908e75bd2a65877e25f9d90c22c848 (patch)
tree00130de15db1164c02b285cde32818ad3c51127a /kernel
parent320b0651f32b830add6497fcdcfdcb6ae8c7b8a0 (diff)
downloadlinux-c917e0f259908e75bd2a65877e25f9d90c22c848.tar.bz2
perf/cgroup: Fix child event counting bug
When a perf_event is attached to parent cgroup, it should count events for all children cgroups: parent_group <---- perf_event \ - child_group <---- process(es) However, in our tests, we found this perf_event cannot report reliable results. Here is an example case: # create cgroups mkdir -p /sys/fs/cgroup/p/c # start perf for parent group perf stat -e instructions -G "p" # on another console, run test process in child cgroup: stressapptest -s 2 -M 1000 & echo $! > /sys/fs/cgroup/p/c/cgroup.procs # after the test process is done, stop perf in the first console shows <not counted> instructions p The instruction should not be "not counted" as the process runs in the child cgroup. We found this is because perf_event->cgrp and cpuctx->cgrp are not identical, thus perf_event->cgrp are not updated properly. This patch fixes this by updating perf_cgroup properly for ancestor cgroup(s). Reported-by: Ephraim Park <ephiepark@fb.com> Signed-off-by: Song Liu <songliubraving@fb.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: <jolsa@redhat.com> Cc: <kernel-team@fb.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Link: http://lkml.kernel.org/r/20180312165943.1057894-1-songliubraving@fb.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/events/core.c21
1 files changed, 16 insertions, 5 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4b838470fac4..709a55b9ad97 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -724,9 +724,15 @@ static inline void __update_cgrp_time(struct perf_cgroup *cgrp)
static inline void update_cgrp_time_from_cpuctx(struct perf_cpu_context *cpuctx)
{
- struct perf_cgroup *cgrp_out = cpuctx->cgrp;
- if (cgrp_out)
- __update_cgrp_time(cgrp_out);
+ struct perf_cgroup *cgrp = cpuctx->cgrp;
+ struct cgroup_subsys_state *css;
+
+ if (cgrp) {
+ for (css = &cgrp->css; css; css = css->parent) {
+ cgrp = container_of(css, struct perf_cgroup, css);
+ __update_cgrp_time(cgrp);
+ }
+ }
}
static inline void update_cgrp_time_from_event(struct perf_event *event)
@@ -754,6 +760,7 @@ perf_cgroup_set_timestamp(struct task_struct *task,
{
struct perf_cgroup *cgrp;
struct perf_cgroup_info *info;
+ struct cgroup_subsys_state *css;
/*
* ctx->lock held by caller
@@ -764,8 +771,12 @@ perf_cgroup_set_timestamp(struct task_struct *task,
return;
cgrp = perf_cgroup_from_task(task, ctx);
- info = this_cpu_ptr(cgrp->info);
- info->timestamp = ctx->timestamp;
+
+ for (css = &cgrp->css; css; css = css->parent) {
+ cgrp = container_of(css, struct perf_cgroup, css);
+ info = this_cpu_ptr(cgrp->info);
+ info->timestamp = ctx->timestamp;
+ }
}
static DEFINE_PER_CPU(struct list_head, cgrp_cpuctx_list);