On Sun, Jul 26, 2015 at 10:40:37PM -0700, Sukadev Bhattiprolu wrote:
> @@ -3743,7 +3762,13 @@ static u64 perf_event_aggregate(struct perf_event *event, u64 *enabled,
> lockdep_assert_held(&event->child_mutex);
>
> list_for_each_entry(child, &event->child_list, child_list) {
> +#if 0
> + /*
> + * TODO: Do we need this read() for group events on PMUs that
> + * don't implement PERF_PMU_TXN_READ transactions?
> + */
> (void)perf_event_read(child, false);
> +#endif
> total += perf_event_count(child);
> *enabled += child->total_time_enabled;
> *running += child->total_time_running;
Aw gawd, I've been an idiot!!
I just realized this is a _CHILD_ loop, not a _SIBLING_ loop !!
We need to flip the loops in perf_read_group(), find attached two
patches that go on top of 1,2,4.
After this you can add the perf_event_read() return value (just fold
patches 6,8) after which you can do patch 10 (which has a broken
Subject fwiw).
Subject: perf: Add group reads to perf_event_read()
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Thu, 23 Jul 2015 10:04:35 +0200
Enable perf_event_read() to update entire groups at once, this will be
useful for read transactions.
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20150723080435.GE25159@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
---
kernel/events/core.c | 39 ++++++++++++++++++++++++++++++++-------
1 file changed, 32 insertions(+), 7 deletions(-)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3184,12 +3184,18 @@ void perf_event_exec(void)
rcu_read_unlock();
}
+struct perf_read_data {
+ struct perf_event *event;
+ bool group;
+};
+
/*
* Cross CPU call to read the hardware event
*/
static void __perf_event_read(void *info)
{
- struct perf_event *event = info;
+ struct perf_read_data *data = info;
+ struct perf_event *sub, *event = data->event;
struct perf_event_context *ctx = event->ctx;
struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
@@ -3208,9 +3214,21 @@ static void __perf_event_read(void *info
update_context_time(ctx);
update_cgrp_time_from_event(event);
}
+
update_event_times(event);
if (event->state == PERF_EVENT_STATE_ACTIVE)
event->pmu->read(event);
+
+ if (!data->group)
+ goto unlock;
+
+ list_for_each_entry(sub, &event->sibling_list, group_entry) {
+ update_event_times(sub);
+ if (sub->state == PERF_EVENT_STATE_ACTIVE)
+ sub->pmu->read(sub);
+ }
+
+unlock:
raw_spin_unlock(&ctx->lock);
}
@@ -3222,15 +3240,19 @@ static inline u64 perf_event_count(struc
return __perf_event_count(event);
}
-static void perf_event_read(struct perf_event *event)
+static void perf_event_read(struct perf_event *event, bool group)
{
/*
* If event is enabled and currently active on a CPU, update the
* value in the event structure:
*/
if (event->state == PERF_EVENT_STATE_ACTIVE) {
+ struct perf_read_data data = {
+ .event = event,
+ .group = group,
+ };
smp_call_function_single(event->oncpu,
- __perf_event_read, event, 1);
+ __perf_event_read, &data, 1);
} else if (event->state == PERF_EVENT_STATE_INACTIVE) {
struct perf_event_context *ctx = event->ctx;
unsigned long flags;
@@ -3245,7 +3267,10 @@ static void perf_event_read(struct perf_
update_context_time(ctx);
update_cgrp_time_from_event(event);
}
- update_event_times(event);
+ if (group)
+ update_group_times(event);
+ else
+ update_event_times(event);
raw_spin_unlock_irqrestore(&ctx->lock, flags);
}
}
@@ -3764,7 +3789,7 @@ u64 perf_event_read_value(struct perf_ev
mutex_lock(&event->child_mutex);
- perf_event_read(event);
+ perf_event_read(event, false);
total += perf_event_count(event);
*enabled += event->total_time_enabled +
@@ -3773,7 +3798,7 @@ u64 perf_event_read_value(struct perf_ev
atomic64_read(&event->child_total_time_running);
list_for_each_entry(child, &event->child_list, child_list) {
- perf_event_read(child);
+ perf_event_read(child, false);
total += perf_event_count(child);
*enabled += child->total_time_enabled;
*running += child->total_time_running;
@@ -3934,7 +3959,7 @@ static unsigned int perf_poll(struct fil
static void _perf_event_reset(struct perf_event *event)
{
- perf_event_read(event);
+ perf_event_read(event, false);
local64_set(&event->count, 0);
perf_event_update_userpage(event);
}
Subject: perf: Invert perf_read_group() loops
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Thu Aug 6 13:41:13 CEST 2015
In order to enable the use of perf_event_read(.group = true), we need
to invert the sibling-child loop nesting of perf_read_group().
Currently we iterate the child list for each sibling, this precludes
using group reads. Flip things around so we iterate each group for
each child.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
kernel/events/core.c | 84 ++++++++++++++++++++++++++++++++-------------------
1 file changed, 54 insertions(+), 30 deletions(-)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3809,50 +3809,74 @@ u64 perf_event_read_value(struct perf_ev
}
EXPORT_SYMBOL_GPL(perf_event_read_value);
-static int perf_read_group(struct perf_event *event,
- u64 read_format, char __user *buf)
+static void __perf_read_group_add(struct perf_event *leader, u64 read_format, u64 *values)
{
- struct perf_event *leader = event->group_leader, *sub;
- struct perf_event_context *ctx = leader->ctx;
- int n = 0, size = 0, ret;
- u64 count, enabled, running;
- u64 values[5];
+ struct perf_event *sub;
+ int n = 1; /* skip @nr */
- lockdep_assert_held(&ctx->mutex);
+ perf_event_read(leader, true);
+
+ /*
+ * Since we co-schedule groups, {enabled,running} times of siblings
+ * will be identical to those of the leader, so we only publish one
+ * set.
+ */
+ if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) {
+ values[n++] += leader->total_time_enabled +
+ atomic64_read(leader->child_total_time_enabled);
+ }
- count = perf_event_read_value(leader, &enabled, &running);
+ if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) {
+ values[n++] += leader->total_time_running +
+ atomic64_read(leader->child_total_time_running);
+ }
- values[n++] = 1 + leader->nr_siblings;
- if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
- values[n++] = enabled;
- if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
- values[n++] = running;
- values[n++] = count;
+ /*
+ * Write {count,id} tuples for every sibling.
+ */
+ values[n++] += perf_event_count(leader);
if (read_format & PERF_FORMAT_ID)
values[n++] = primary_event_id(leader);
- size = n * sizeof(u64);
+ list_for_each_entry(sub, &leader->sibling_list, group_entry) {
+ values[n++] += perf_event_count(sub);
+ if (read_format & PERF_FORMAT_ID)
+ values[n++] = primary_event_id(sub);
+ }
+}
- if (copy_to_user(buf, values, size))
- return -EFAULT;
+static int perf_read_group(struct perf_event *event,
+ u64 read_format, char __user *buf)
+{
+ struct perf_event *leader = event->group_leader, *child;
+ struct perf_event_context *ctx = leader->ctx;
+ int ret = leader->read_size;
+ u64 *values;
- ret = size;
+ lockdep_assert_held(&ctx->mutex);
- list_for_each_entry(sub, &leader->sibling_list, group_entry) {
- n = 0;
+ values = kzalloc(event->read_size);
+ if (!values)
+ return -ENOMEM;
- values[n++] = perf_event_read_value(sub, &enabled, &running);
- if (read_format & PERF_FORMAT_ID)
- values[n++] = primary_event_id(sub);
+ values[0] = 1 + leader->nr_siblings;
- size = n * sizeof(u64);
+ /*
+ * By locking the child_mutex of the leader we effectively
+ * lock the child list of all siblings.. XXX explain how.
+ */
+ mutex_lock(&leader->child_mutex);
- if (copy_to_user(buf + ret, values, size)) {
- return -EFAULT;
- }
+ __perf_read_group_add(leader, read_format, values);
+ list_for_each_entry(child, &leader->child_list, child_list)
+ __perf_read_group_add(child, read_format, values);
- ret += size;
- }
+ mutex_unlock(&leader->child_mutex);
+
+ if (copy_to_user(buf, values, event->read_size))
+ ret = -EFAULT;
+
+ kfree(values);
return ret;
}
