4.14-stable review patch. If anyone has any objections, please let me know.
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From: Song Liu songliubraving@fb.com
[ Upstream commit c917e0f259908e75bd2a65877e25f9d90c22c848 ]
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 Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/events/core.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-)
--- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -642,9 +642,15 @@ static inline void __update_cgrp_time(st
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) @@ -672,6 +678,7 @@ perf_cgroup_set_timestamp(struct task_st { struct perf_cgroup *cgrp; struct perf_cgroup_info *info; + struct cgroup_subsys_state *css;
/* * ctx->lock held by caller @@ -682,8 +689,12 @@ perf_cgroup_set_timestamp(struct task_st 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);