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Subject[PATCH v6 5/6] perf/cgroup: Grow per perf_cpu_context heap storage
From
Allow the per-CPU min heap storage to have sufficient space for per-cgroup
iterators.

Based-on-work-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ian Rogers <irogers@google.com>
---
kernel/events/core.c | 47 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 47 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 18e4bb871d85..4eb4e67463bf 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -892,6 +892,47 @@ static inline void perf_cgroup_sched_in(struct task_struct *prev,
rcu_read_unlock();
}

+static int perf_cgroup_ensure_storage(struct perf_event *event,
+ struct cgroup_subsys_state *css)
+{
+ struct perf_cpu_context *cpuctx;
+ struct perf_event **storage;
+ int cpu, itr_cap, ret = 0;
+
+ /*
+ * Allow storage to have sufficent space for an iterator for each
+ * possibly nested cgroup plus an iterator for events with no cgroup.
+ */
+ for (itr_cap = 1; css; css = css->parent)
+ itr_cap++;
+
+ for_each_possible_cpu(cpu) {
+ cpuctx = per_cpu_ptr(event->pmu->pmu_cpu_context, cpu);
+ if (itr_cap <= cpuctx->itr_storage_cap)
+ continue;
+
+ storage = kmalloc_node(itr_cap * sizeof(struct perf_event *),
+ GFP_KERNEL, cpu_to_node(cpu));
+ if (!storage) {
+ ret = -ENOMEM;
+ break;
+ }
+
+ raw_spin_lock_irq(&cpuctx->ctx.lock);
+ if (cpuctx->itr_storage_cap < itr_cap) {
+ swap(cpuctx->itr_storage, storage);
+ if (storage == cpuctx->itr_default)
+ storage = NULL;
+ cpuctx->itr_storage_cap = itr_cap;
+ }
+ raw_spin_unlock_irq(&cpuctx->ctx.lock);
+
+ kfree(storage);
+ }
+
+ return ret;
+}
+
static inline int perf_cgroup_connect(int fd, struct perf_event *event,
struct perf_event_attr *attr,
struct perf_event *group_leader)
@@ -911,6 +952,10 @@ static inline int perf_cgroup_connect(int fd, struct perf_event *event,
goto out;
}

+ ret = perf_cgroup_ensure_storage(event, css);
+ if (ret)
+ goto out;
+
cgrp = container_of(css, struct perf_cgroup, css);
event->cgrp = cgrp;

@@ -3437,6 +3482,8 @@ static noinline int visit_groups_merge(struct perf_cpu_context *cpuctx,
.size = 0,
.cap = cpuctx->itr_storage_cap,
};
+
+ lockdep_assert_held(&cpuctx->ctx.lock);
} else {
event_heap = (struct min_heap){
.data = itrs,
--
2.25.0.265.gbab2e86ba0-goog
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