Messages in this thread Patch in this message | | | Date | Fri, 6 Dec 2019 15:15:37 -0800 | Subject | [PATCH v5 08/10] perf: cache perf_event_groups_first for cgroups | From | Ian Rogers <> |
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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.
Based-on-work-by: Kan Liang <kan.liang@linux.intel.com> Signed-off-by: Ian Rogers <irogers@google.com> --- include/linux/perf_event.h | 7 ++++ kernel/events/core.c | 84 ++++++++++++++++++++++++++++++++++---- 2 files changed, 82 insertions(+), 9 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index cd7d3b624655..a29a38df909e 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -892,6 +892,13 @@ 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 3da9cc1ebc2d..5935d2474050 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -1638,6 +1638,27 @@ 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); + } + /* + * Remember smallest, left-most, group index event. The + * less-than condition is only possible if the group_index + * overflows. + */ + if (!*cgrp_event || + event->group_index < (*cgrp_event)->group_index) + *cgrp_event = event; + } +#endif } /* @@ -1652,6 +1673,9 @@ 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. */ @@ -1662,6 +1686,22 @@ 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); } @@ -1679,7 +1719,8 @@ 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, @@ -3596,8 +3637,8 @@ static int ctx_groups_sched_in(struct perf_event_context *ctx, .cap = ARRAY_SIZE(itrs), }; /* Events not within a CPU context may be on any CPU. */ - __heap_add(&event_heap, perf_event_groups_first(groups, -1, - NULL)); + __heap_add(&event_heap, + perf_event_groups_first(groups, -1, NULL)); } evt = event_heap.data; @@ -3605,8 +3646,16 @@ static int ctx_groups_sched_in(struct perf_event_context *ctx, #ifdef CONFIG_CGROUP_PERF for (; css; css = css->parent) { - __heap_add(&event_heap, perf_event_groups_first(groups, cpu, - css->cgroup)); + struct perf_cgroup *cgrp; + + /* root cgroup doesn't have events */ + if (css->id == 1) + break; + + cgrp = container_of(css, struct perf_cgroup, css); + __heap_add(&event_heap, is_pinned + ? *per_cpu_ptr(cgrp->pinned_event, cpu) + : *per_cpu_ptr(cgrp->flexible_event, cpu)); } #endif @@ -12672,18 +12721,35 @@ 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); } -- 2.24.0.393.g34dc348eaf-goog
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