[PATCH 5/7] perf: cache perf_event_groups_first for cgroups
From: Ian Rogers
Date: Tue Jul 02 2019 - 03:00:36 EST
Add a per-CPU cache of the pinned and flexible perf_event_groups_first
value for a cgroup avoiding an O(log(#perf events)) searches during
sched_in.
This patch is derived from an original patch by Kan Liang
<kan.liang@xxxxxxxxxxxxxxx>
Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
include/linux/perf_event.h | 6 ++
kernel/events/core.c | 142 ++++++++++++++++++++++++++-----------
2 files changed, 106 insertions(+), 42 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 5c479f61622c..86fb379296cb 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -845,6 +845,12 @@ struct perf_cgroup_info {
struct perf_cgroup {
struct cgroup_subsys_state css;
struct perf_cgroup_info __percpu *info;
+ /* A cache of the first event with the perf_cpu_context's
+ * perf_event_context for the first event in pinned_groups or
+ * flexible_groups. Avoids an rbtree search during sched_in.
+ */
+ struct perf_event * __percpu *pinned_event;
+ struct perf_event * __percpu *flexible_event;
};
/*
diff --git a/kernel/events/core.c b/kernel/events/core.c
index a2c5ea868de9..7608bd562dac 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1594,6 +1594,25 @@ perf_event_groups_insert(struct perf_event_groups *groups,
rb_link_node(&event->group_node, parent, node);
rb_insert_color(&event->group_node, &groups->tree);
+#ifdef CONFIG_CGROUP_PERF
+ if (is_cgroup_event(event)) {
+ struct perf_event **cgrp_event;
+
+ if (event->attr.pinned)
+ cgrp_event = per_cpu_ptr(event->cgrp->pinned_event,
+ event->cpu);
+ else
+ cgrp_event = per_cpu_ptr(event->cgrp->flexible_event,
+ event->cpu);
+ /*
+ * Cgroup events for the same cgroup on the same CPU will
+ * always be inserted at the right because of bigger
+ * @groups->index. Only need to set *cgrp_event when it's NULL.
+ */
+ if (!*cgrp_event)
+ *cgrp_event = event;
+ }
+#endif
}
/*
@@ -1608,6 +1627,9 @@ add_event_to_groups(struct perf_event *event, struct perf_event_context *ctx)
perf_event_groups_insert(groups, event);
}
+static struct perf_event *
+perf_event_groups_next(struct perf_event *event);
+
/*
* Delete a group from a tree.
*/
@@ -1618,6 +1640,22 @@ perf_event_groups_delete(struct perf_event_groups *groups,
WARN_ON_ONCE(RB_EMPTY_NODE(&event->group_node) ||
RB_EMPTY_ROOT(&groups->tree));
+#ifdef CONFIG_CGROUP_PERF
+ if (is_cgroup_event(event)) {
+ struct perf_event **cgrp_event;
+
+ if (event->attr.pinned)
+ cgrp_event = per_cpu_ptr(event->cgrp->pinned_event,
+ event->cpu);
+ else
+ cgrp_event = per_cpu_ptr(event->cgrp->flexible_event,
+ event->cpu);
+
+ if (*cgrp_event == event)
+ *cgrp_event = perf_event_groups_next(event);
+ }
+#endif
+
rb_erase(&event->group_node, &groups->tree);
init_event_group(event);
}
@@ -1635,20 +1673,14 @@ del_event_from_groups(struct perf_event *event, struct perf_event_context *ctx)
}
/*
- * Get the leftmost event in the cpu/cgroup subtree.
+ * Get the leftmost event in the cpu subtree without a cgroup (ie task or
+ * system-wide).
*/
static struct perf_event *
-perf_event_groups_first(struct perf_event_groups *groups, int cpu,
- struct cgroup *cgrp)
+perf_event_groups_first_no_cgroup(struct perf_event_groups *groups, int cpu)
{
struct perf_event *node_event = NULL, *match = NULL;
struct rb_node *node = groups->tree.rb_node;
-#ifdef CONFIG_CGROUP_PERF
- int node_cgrp_id, cgrp_id = 0;
-
- if (cgrp)
- cgrp_id = cgrp->id;
-#endif
while (node) {
node_event = container_of(node, struct perf_event, group_node);
@@ -1662,18 +1694,10 @@ perf_event_groups_first(struct perf_event_groups *groups, int cpu,
continue;
}
#ifdef CONFIG_CGROUP_PERF
- node_cgrp_id = 0;
- if (node_event->cgrp && node_event->cgrp->css.cgroup)
- node_cgrp_id = node_event->cgrp->css.cgroup->id;
-
- if (cgrp_id < node_cgrp_id) {
+ if (node_event->cgrp) {
node = node->rb_left;
continue;
}
- if (cgrp_id > node_cgrp_id) {
- node = node->rb_right;
- continue;
- }
#endif
match = node_event;
node = node->rb_left;
@@ -3428,6 +3452,13 @@ static void min_heap_pop_push(struct perf_event_heap *heap,
}
}
+static int pinned_sched_in(struct perf_event_context *ctx,
+ struct perf_cpu_context *cpuctx,
+ struct perf_event *event);
+static int flexible_sched_in(struct perf_event_context *ctx,
+ struct perf_cpu_context *cpuctx,
+ struct perf_event *event,
+ int *can_add_hw);
/*
* Without cgroups, with a task context, there may be per-CPU and any
@@ -3437,11 +3468,7 @@ static void min_heap_pop_push(struct perf_event_heap *heap,
static int visit_groups_merge(struct perf_event_context *ctx,
struct perf_cpu_context *cpuctx,
- struct perf_event_groups *groups,
- int (*func)(struct perf_event_context *,
- struct perf_cpu_context *,
- struct perf_event *,
- int *),
+ bool is_pinned,
int *data)
{
/*
@@ -3467,7 +3494,11 @@ static int visit_groups_merge(struct perf_event_context *ctx,
#endif
int ret, cpu = smp_processor_id();
- heap.storage[0] = perf_event_groups_first(groups, cpu, NULL);
+ struct perf_event_groups *groups = is_pinned
+ ? &ctx->pinned_groups
+ : &ctx->flexible_groups;
+
+ heap.storage[0] = perf_event_groups_first_no_cgroup(groups, cpu);
if (heap.storage[0])
heap.num_elements++;
@@ -3477,7 +3508,7 @@ static int visit_groups_merge(struct perf_event_context *ctx,
* events.
*/
heap.storage[heap.num_elements] =
- perf_event_groups_first(groups, -1, NULL);
+ perf_event_groups_first_no_cgroup(groups, -1);
if (heap.storage[heap.num_elements])
heap.num_elements++;
} else {
@@ -3487,14 +3518,22 @@ static int visit_groups_merge(struct perf_event_context *ctx,
* For itrs[1..MAX] add an iterator for each cgroup parent that
* has events.
*/
- if (cpuctx->cgrp) {
+ struct perf_cgroup *cgrp = cpuctx->cgrp;
+
+ if (cgrp) {
struct cgroup_subsys_state *css;
- for (css = &cpuctx->cgrp->css; css; css = css->parent) {
- heap.storage[heap.num_elements] =
- perf_event_groups_first(groups,
- cpu,
- css->cgroup);
+ for (css = &cgrp->css; css; css = css->parent) {
+ /* root cgroup doesn't have events */
+ if (css->id == 1)
+ break;
+
+ cgrp = container_of(css, struct perf_cgroup,
+ css);
+ heap.storage[heap.num_elements] = is_pinned
+ ? *per_cpu_ptr(cgrp->pinned_event, cpu)
+ : *per_cpu_ptr(cgrp->flexible_event,
+ cpu);
if (heap.storage[heap.num_elements]) {
heap.num_elements++;
if (heap.num_elements ==
@@ -3511,7 +3550,12 @@ static int visit_groups_merge(struct perf_event_context *ctx,
min_heapify_all(&heap);
while (heap.num_elements > 0) {
- ret = func(ctx, cpuctx, heap.storage[0], data);
+ if (is_pinned)
+ ret = pinned_sched_in(ctx, cpuctx, heap.storage[0]);
+ else
+ ret = flexible_sched_in(ctx, cpuctx, heap.storage[0],
+ data);
+
if (ret)
return ret;
@@ -3524,8 +3568,7 @@ static int visit_groups_merge(struct perf_event_context *ctx,
static int pinned_sched_in(struct perf_event_context *ctx,
struct perf_cpu_context *cpuctx,
- struct perf_event *event,
- int *unused)
+ struct perf_event *event)
{
if (event->state <= PERF_EVENT_STATE_OFF)
return 0;
@@ -3578,8 +3621,7 @@ ctx_pinned_sched_in(struct perf_event_context *ctx,
{
visit_groups_merge(ctx,
cpuctx,
- &ctx->pinned_groups,
- pinned_sched_in,
+ /*is_pinned=*/true,
NULL);
}
@@ -3591,8 +3633,7 @@ ctx_flexible_sched_in(struct perf_event_context *ctx,
visit_groups_merge(ctx,
cpuctx,
- &ctx->flexible_groups,
- flexible_sched_in,
+ /*is_pinned=*/false,
&can_add_hw);
}
@@ -12374,18 +12415,35 @@ perf_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
return ERR_PTR(-ENOMEM);
jc->info = alloc_percpu(struct perf_cgroup_info);
- if (!jc->info) {
- kfree(jc);
- return ERR_PTR(-ENOMEM);
- }
+ if (!jc->info)
+ goto free_jc;
+
+ jc->pinned_event = alloc_percpu(struct perf_event *);
+ if (!jc->pinned_event)
+ goto free_jc_info;
+
+ jc->flexible_event = alloc_percpu(struct perf_event *);
+ if (!jc->flexible_event)
+ goto free_jc_pinned;
return &jc->css;
+
+free_jc_pinned:
+ free_percpu(jc->pinned_event);
+free_jc_info:
+ free_percpu(jc->info);
+free_jc:
+ kfree(jc);
+
+ return ERR_PTR(-ENOMEM);
}
static void perf_cgroup_css_free(struct cgroup_subsys_state *css)
{
struct perf_cgroup *jc = container_of(css, struct perf_cgroup, css);
+ free_percpu(jc->pinned_event);
+ free_percpu(jc->flexible_event);
free_percpu(jc->info);
kfree(jc);
}
--
2.22.0.410.gd8fdbe21b5-goog