Messages in this thread Patch in this message | | | From | Song Liu <> | Subject | [PATCH v2] perf: update perf_cgroup time for ancestor cgroup(s) | Date | Mon, 12 Mar 2018 09:59:43 -0700 |
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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).
Signed-off-by: Song Liu <songliubraving@fb.com> Reported-by: Ephraim Park <ephiepark@fb.com> --- kernel/events/core.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c index 5789810..6f015ff 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -724,9 +724,14 @@ 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 +759,7 @@ 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 +770,12 @@ 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); -- 2.9.5
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