Re: [RFC][PATCH 4/7] perf: Fix scaling vs enable_on_exec
From: Peter Zijlstra
Date: Wed Feb 24 2016 - 06:54:19 EST
On Tue, Feb 23, 2016 at 06:47:41PM +0100, Peter Zijlstra wrote:
> On Tue, Feb 23, 2016 at 10:05:50PM +0530, Pratyush Anand wrote:
> > Its better with this patch, still count is 1 more in case of higher probe hits (
> > like 65535 times).
>
> Ah, ok, I'll go try again.
OK, so the below seems to cure this for me, but now I'm hurting my head
to make the same true for perf_install_in_context(), because 'tricky' :/
(the below is a fold of 2 patches, I'll send out a new series once I get
my head around the install_in_context muck :/)
---
kernel/events/core.c | 84 +++++++++++++++++++++++++++++++++-------------------
1 file changed, 53 insertions(+), 31 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 94c47e3f9a0a..8326a7f5729c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -314,7 +314,8 @@ static void event_function_call(struct perf_event *event, event_f func, void *da
enum event_type_t {
EVENT_FLEXIBLE = 0x1,
EVENT_PINNED = 0x2,
- EVENT_ALL = EVENT_FLEXIBLE | EVENT_PINNED,
+ EVENT_TIME = 0x4,
+ EVENT_ALL = EVENT_FLEXIBLE | EVENT_PINNED | EVENT_TIME,
};
/*
@@ -1288,16 +1289,18 @@ static u64 perf_event_time(struct perf_event *event)
/*
* Update the total_time_enabled and total_time_running fields for a event.
- * The caller of this function needs to hold the ctx->lock.
*/
static void update_event_times(struct perf_event *event)
{
struct perf_event_context *ctx = event->ctx;
u64 run_end;
+ lockdep_assert_held(&ctx->lock);
+
if (event->state < PERF_EVENT_STATE_INACTIVE ||
event->group_leader->state < PERF_EVENT_STATE_INACTIVE)
return;
+
/*
* in cgroup mode, time_enabled represents
* the time the event was enabled AND active
@@ -2063,14 +2066,27 @@ static void add_event_to_ctx(struct perf_event *event,
event->tstamp_stopped = tstamp;
}
-static void task_ctx_sched_out(struct perf_cpu_context *cpuctx,
- struct perf_event_context *ctx);
+static void ctx_sched_out(struct perf_event_context *ctx,
+ struct perf_cpu_context *cpuctx,
+ enum event_type_t event_type);
static void
ctx_sched_in(struct perf_event_context *ctx,
struct perf_cpu_context *cpuctx,
enum event_type_t event_type,
struct task_struct *task);
+static void task_ctx_sched_out(struct perf_cpu_context *cpuctx,
+ struct perf_event_context *ctx)
+{
+ if (!cpuctx->task_ctx)
+ return;
+
+ if (WARN_ON_ONCE(ctx != cpuctx->task_ctx))
+ return;
+
+ ctx_sched_out(ctx, cpuctx, EVENT_ALL);
+}
+
static void perf_event_sched_in(struct perf_cpu_context *cpuctx,
struct perf_event_context *ctx,
struct task_struct *task)
@@ -2219,17 +2235,17 @@ static void __perf_event_enable(struct perf_event *event,
event->state <= PERF_EVENT_STATE_ERROR)
return;
- update_context_time(ctx);
+ ctx_sched_out(ctx, cpuctx, EVENT_TIME);
+
__perf_event_mark_enabled(event);
if (!ctx->is_active)
return;
if (!event_filter_match(event)) {
- if (is_cgroup_event(event)) {
- perf_cgroup_set_timestamp(current, ctx); // XXX ?
+ if (is_cgroup_event(event))
perf_cgroup_defer_enabled(event);
- }
+ ctx_sched_in(ctx, cpuctx, EVENT_TIME, current);
return;
}
@@ -2237,8 +2253,10 @@ static void __perf_event_enable(struct perf_event *event,
* If the event is in a group and isn't the group leader,
* then don't put it on unless the group is on.
*/
- if (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE)
+ if (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE) {
+ ctx_sched_in(ctx, cpuctx, EVENT_TIME, current);
return;
+ }
task_ctx = cpuctx->task_ctx;
if (ctx->task)
@@ -2344,24 +2362,33 @@ static void ctx_sched_out(struct perf_event_context *ctx,
}
ctx->is_active &= ~event_type;
+ if (!(ctx->is_active & (EVENT_FLEXIBLE | EVENT_PINNED)))
+ ctx->is_active = 0;
+
if (ctx->task) {
WARN_ON_ONCE(cpuctx->task_ctx != ctx);
if (!ctx->is_active)
cpuctx->task_ctx = NULL;
}
- update_context_time(ctx);
- update_cgrp_time_from_cpuctx(cpuctx);
+ is_active ^= ctx->is_active; /* changed bits */
+
+ if (is_active & EVENT_TIME) {
+ /* update (and stop) ctx time */
+ update_context_time(ctx);
+ update_cgrp_time_from_cpuctx(cpuctx);
+ }
+
if (!ctx->nr_active)
return;
perf_pmu_disable(ctx->pmu);
- if ((is_active & EVENT_PINNED) && (event_type & EVENT_PINNED)) {
+ if (is_active & EVENT_PINNED) {
list_for_each_entry(event, &ctx->pinned_groups, group_entry)
group_sched_out(event, cpuctx, ctx);
}
- if ((is_active & EVENT_FLEXIBLE) && (event_type & EVENT_FLEXIBLE)) {
+ if (is_active & EVENT_FLEXIBLE) {
list_for_each_entry(event, &ctx->flexible_groups, group_entry)
group_sched_out(event, cpuctx, ctx);
}
@@ -2641,18 +2668,6 @@ void __perf_event_task_sched_out(struct task_struct *task,
perf_cgroup_sched_out(task, next);
}
-static void task_ctx_sched_out(struct perf_cpu_context *cpuctx,
- struct perf_event_context *ctx)
-{
- if (!cpuctx->task_ctx)
- return;
-
- if (WARN_ON_ONCE(ctx != cpuctx->task_ctx))
- return;
-
- ctx_sched_out(ctx, cpuctx, EVENT_ALL);
-}
-
/*
* Called with IRQs disabled
*/
@@ -2735,7 +2750,7 @@ ctx_sched_in(struct perf_event_context *ctx,
if (likely(!ctx->nr_events))
return;
- ctx->is_active |= event_type;
+ ctx->is_active |= (event_type | EVENT_TIME);
if (ctx->task) {
if (!is_active)
cpuctx->task_ctx = ctx;
@@ -2743,18 +2758,24 @@ ctx_sched_in(struct perf_event_context *ctx,
WARN_ON_ONCE(cpuctx->task_ctx != ctx);
}
- now = perf_clock();
- ctx->timestamp = now;
- perf_cgroup_set_timestamp(task, ctx);
+ is_active ^= ctx->is_active; /* changed bits */
+
+ if (is_active & EVENT_TIME) {
+ /* start ctx time */
+ now = perf_clock();
+ ctx->timestamp = now;
+ perf_cgroup_set_timestamp(task, ctx);
+ }
+
/*
* First go through the list and put on any pinned groups
* in order to give them the best chance of going on.
*/
- if (!(is_active & EVENT_PINNED) && (event_type & EVENT_PINNED))
+ if (is_active & EVENT_PINNED)
ctx_pinned_sched_in(ctx, cpuctx);
/* Then walk through the lower prio flexible groups */
- if (!(is_active & EVENT_FLEXIBLE) && (event_type & EVENT_FLEXIBLE))
+ if (is_active & EVENT_FLEXIBLE)
ctx_flexible_sched_in(ctx, cpuctx);
}
@@ -3120,6 +3141,7 @@ static void perf_event_enable_on_exec(int ctxn)
cpuctx = __get_cpu_context(ctx);
perf_ctx_lock(cpuctx, ctx);
+ ctx_sched_out(ctx, cpuctx, EVENT_TIME);
list_for_each_entry(event, &ctx->event_list, event_entry)
enabled |= event_enable_on_exec(event, ctx);