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Message-ID: <20150723080435.GE25159@twins.programming.kicks-ass.net>
Date: Thu, 23 Jul 2015 10:04:35 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Michael Ellerman <mpe@...erman.id.au>,
linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
linux-s390@...r.kernel.org, sparclinux@...r.kernel.org
Subject: Re: [PATCH v3 7/8] perf: Define PMU_TXN_READ interface
On Wed, Jul 22, 2015 at 04:19:16PM -0700, Sukadev Bhattiprolu wrote:
> Peter Zijlstra [peterz@...radead.org] wrote:
> | I've not woken up yet, and not actually fully read the email, but can
> | you stuff the entire above chunk inside the IPI?
> |
> | I think you could then actually optimize __perf_event_read() as well,
> | because all these events should be on the same context, so no point in
> | calling update_*time*() for every event or so.
> |
>
> Do you mean something like this (will move the rename to a separate
> patch before posting):
More like so.. please double check, I've not even had tea yet.
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3174,14 +3174,22 @@ void perf_event_exec(void)
rcu_read_unlock();
}
+struct perf_read_data {
+ struct perf_event *event;
+ bool group;
+ int ret;
+};
+
/*
* 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);
+ struct pmu *pmu = event->pmu;
/*
* If this is a task context, we need to check whether it is
@@ -3199,8 +3207,23 @@ static void __perf_event_read(void *info
update_cgrp_time_from_event(event);
}
update_event_times(event);
- if (event->state == PERF_EVENT_STATE_ACTIVE)
- event->pmu->read(event);
+ if (event->state != PERF_EVENT_STATE_ACTIVE)
+ goto unlock;
+
+ if (!data->group) {
+ pmu->read(event);
+ goto unlock;
+ }
+
+ pmu->start_txn(pmu, PERF_PMU_TXN_READ);
+ pmu->read(event);
+ list_for_each_entry(sub, &event->sibling_list, group_entry) {
+ if (sub->state == PERF_EVENT_STATE_ACTIVE)
+ pmu->read(sub);
+ }
+ data->ret = pmu->commit_txn(pmu);
+
+unlock:
raw_spin_unlock(&ctx->lock);
}
@@ -3212,15 +3235,23 @@ static inline u64 perf_event_count(struc
return __perf_event_count(event);
}
-static void perf_event_read(struct perf_event *event)
+static int perf_event_read(struct perf_event *event, bool group)
{
+ int ret = 0
+
/*
* 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,
+ .ret = 0,
+ };
smp_call_function_single(event->oncpu,
- __perf_event_read, event, 1);
+ __perf_event_read, &data, 1);
+ ret = data.ret;
} else if (event->state == PERF_EVENT_STATE_INACTIVE) {
struct perf_event_context *ctx = event->ctx;
unsigned long flags;
@@ -3235,9 +3266,14 @@ 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);
}
+
+ return ret;
}
/*
@@ -3718,7 +3754,6 @@ static u64 perf_event_compute(struct per
atomic64_read(&event->child_total_time_running);
list_for_each_entry(child, &event->child_list, child_list) {
- perf_event_read(child);
total += perf_event_count(child);
*enabled += child->total_time_enabled;
*running += child->total_time_running;
@@ -3772,7 +3807,7 @@ 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_compute(event, enabled, running);
mutex_unlock(&event->child_mutex);
@@ -3792,7 +3827,11 @@ static int perf_read_group(struct perf_e
lockdep_assert_held(&ctx->mutex);
- count = perf_event_read_value(leader, &enabled, &running);
+ ret = perf_event_read(leader, true);
+ if (ret)
+ return ret;
+
+ count = perf_event_compute(leader, &enabled, &running);
values[n++] = 1 + leader->nr_siblings;
if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
@@ -3813,7 +3852,7 @@ static int perf_read_group(struct perf_e
list_for_each_entry(sub, &leader->sibling_list, group_entry) {
n = 0;
- values[n++] = perf_event_read_value(sub, &enabled, &running);
+ values[n++] = perf_event_compute(sub, &enabled, &running);
if (read_format & PERF_FORMAT_ID)
values[n++] = primary_event_id(sub);
@@ -3931,7 +3970,7 @@ 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);
}
--
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