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Date: Tue, 7 Apr 2009 09:09:00 GMT
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
To: linux-tip-commits@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, paulus@...ba.org, hpa@...or.com,
mingo@...hat.com, a.p.zijlstra@...llo.nl, tglx@...utronix.de,
cjashfor@...ux.vnet.ibm.com, mingo@...e.hu
Subject: [tip:perfcounters/core] perf_counter: rework context time
Commit-ID: 4af4998b8aa35600f4c4a4f3c3a23baca6081d02
Gitweb: http://git.kernel.org/tip/4af4998b8aa35600f4c4a4f3c3a23baca6081d02
Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Mon, 6 Apr 2009 11:45:10 +0200
Committer: Ingo Molnar <mingo@...e.hu>
CommitDate: Tue, 7 Apr 2009 10:49:00 +0200
perf_counter: rework context time
Since perf_counter_context is switched along with tasks, we can
maintain the context time without using the task runtime clock.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Corey Ashford <cjashfor@...ux.vnet.ibm.com>
LKML-Reference: <20090406094518.353552838@...llo.nl>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
include/linux/perf_counter.h | 10 ++----
kernel/perf_counter.c | 78 ++++++++++++++++++-----------------------
2 files changed, 37 insertions(+), 51 deletions(-)
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 0f5a400..7f5d353 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -477,14 +477,10 @@ struct perf_counter_context {
struct task_struct *task;
/*
- * time_now is the current time in nanoseconds since an arbitrary
- * point in the past. For per-task counters, this is based on the
- * task clock, and for per-cpu counters it is based on the cpu clock.
- * time_lost is an offset from the task/cpu clock, used to make it
- * appear that time only passes while the context is scheduled in.
+ * Context clock, runs when context enabled.
*/
- u64 time_now;
- u64 time_lost;
+ u64 time;
+ u64 timestamp;
#endif
};
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 8c8eaf0..84d85ab 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -117,7 +117,7 @@ counter_sched_out(struct perf_counter *counter,
return;
counter->state = PERF_COUNTER_STATE_INACTIVE;
- counter->tstamp_stopped = ctx->time_now;
+ counter->tstamp_stopped = ctx->time;
counter->hw_ops->disable(counter);
counter->oncpu = -1;
@@ -253,27 +253,20 @@ retry:
spin_unlock_irq(&ctx->lock);
}
-/*
- * Get the current time for this context.
- * If this is a task context, we use the task's task clock,
- * or for a per-cpu context, we use the cpu clock.
- */
-static u64 get_context_time(struct perf_counter_context *ctx, int update)
+static inline u64 perf_clock(void)
{
- struct task_struct *curr = ctx->task;
-
- if (!curr)
- return cpu_clock(smp_processor_id());
-
- return __task_delta_exec(curr, update) + curr->se.sum_exec_runtime;
+ return cpu_clock(smp_processor_id());
}
/*
* Update the record of the current time in a context.
*/
-static void update_context_time(struct perf_counter_context *ctx, int update)
+static void update_context_time(struct perf_counter_context *ctx)
{
- ctx->time_now = get_context_time(ctx, update) - ctx->time_lost;
+ u64 now = perf_clock();
+
+ ctx->time += now - ctx->timestamp;
+ ctx->timestamp = now;
}
/*
@@ -284,15 +277,17 @@ static void update_counter_times(struct perf_counter *counter)
struct perf_counter_context *ctx = counter->ctx;
u64 run_end;
- if (counter->state >= PERF_COUNTER_STATE_INACTIVE) {
- counter->total_time_enabled = ctx->time_now -
- counter->tstamp_enabled;
- if (counter->state == PERF_COUNTER_STATE_INACTIVE)
- run_end = counter->tstamp_stopped;
- else
- run_end = ctx->time_now;
- counter->total_time_running = run_end - counter->tstamp_running;
- }
+ if (counter->state < PERF_COUNTER_STATE_INACTIVE)
+ return;
+
+ counter->total_time_enabled = ctx->time - counter->tstamp_enabled;
+
+ if (counter->state == PERF_COUNTER_STATE_INACTIVE)
+ run_end = counter->tstamp_stopped;
+ else
+ run_end = ctx->time;
+
+ counter->total_time_running = run_end - counter->tstamp_running;
}
/*
@@ -332,7 +327,7 @@ static void __perf_counter_disable(void *info)
* If it is in error state, leave it in error state.
*/
if (counter->state >= PERF_COUNTER_STATE_INACTIVE) {
- update_context_time(ctx, 1);
+ update_context_time(ctx);
update_counter_times(counter);
if (counter == counter->group_leader)
group_sched_out(counter, cpuctx, ctx);
@@ -426,7 +421,7 @@ counter_sched_in(struct perf_counter *counter,
return -EAGAIN;
}
- counter->tstamp_running += ctx->time_now - counter->tstamp_stopped;
+ counter->tstamp_running += ctx->time - counter->tstamp_stopped;
if (!is_software_counter(counter))
cpuctx->active_oncpu++;
@@ -493,9 +488,9 @@ static void add_counter_to_ctx(struct perf_counter *counter,
list_add_counter(counter, ctx);
ctx->nr_counters++;
counter->prev_state = PERF_COUNTER_STATE_OFF;
- counter->tstamp_enabled = ctx->time_now;
- counter->tstamp_running = ctx->time_now;
- counter->tstamp_stopped = ctx->time_now;
+ counter->tstamp_enabled = ctx->time;
+ counter->tstamp_running = ctx->time;
+ counter->tstamp_stopped = ctx->time;
}
/*
@@ -522,7 +517,7 @@ static void __perf_install_in_context(void *info)
curr_rq_lock_irq_save(&flags);
spin_lock(&ctx->lock);
- update_context_time(ctx, 1);
+ update_context_time(ctx);
/*
* Protect the list operation against NMI by disabling the
@@ -648,13 +643,13 @@ static void __perf_counter_enable(void *info)
curr_rq_lock_irq_save(&flags);
spin_lock(&ctx->lock);
- update_context_time(ctx, 1);
+ update_context_time(ctx);
counter->prev_state = counter->state;
if (counter->state >= PERF_COUNTER_STATE_INACTIVE)
goto unlock;
counter->state = PERF_COUNTER_STATE_INACTIVE;
- counter->tstamp_enabled = ctx->time_now - counter->total_time_enabled;
+ counter->tstamp_enabled = ctx->time - counter->total_time_enabled;
/*
* If the counter is in a group and isn't the group leader,
@@ -737,8 +732,8 @@ static void perf_counter_enable(struct perf_counter *counter)
*/
if (counter->state == PERF_COUNTER_STATE_OFF) {
counter->state = PERF_COUNTER_STATE_INACTIVE;
- counter->tstamp_enabled = ctx->time_now -
- counter->total_time_enabled;
+ counter->tstamp_enabled =
+ ctx->time - counter->total_time_enabled;
}
out:
spin_unlock_irq(&ctx->lock);
@@ -778,7 +773,7 @@ void __perf_counter_sched_out(struct perf_counter_context *ctx,
ctx->is_active = 0;
if (likely(!ctx->nr_counters))
goto out;
- update_context_time(ctx, 0);
+ update_context_time(ctx);
flags = hw_perf_save_disable();
if (ctx->nr_active) {
@@ -883,12 +878,7 @@ __perf_counter_sched_in(struct perf_counter_context *ctx,
if (likely(!ctx->nr_counters))
goto out;
- /*
- * Add any time since the last sched_out to the lost time
- * so it doesn't get included in the total_time_enabled and
- * total_time_running measures for counters in the context.
- */
- ctx->time_lost = get_context_time(ctx, 0) - ctx->time_now;
+ ctx->timestamp = perf_clock();
flags = hw_perf_save_disable();
@@ -1043,8 +1033,8 @@ int perf_counter_task_enable(void)
if (counter->state > PERF_COUNTER_STATE_OFF)
continue;
counter->state = PERF_COUNTER_STATE_INACTIVE;
- counter->tstamp_enabled = ctx->time_now -
- counter->total_time_enabled;
+ counter->tstamp_enabled =
+ ctx->time - counter->total_time_enabled;
counter->hw_event.disabled = 0;
}
hw_perf_restore(perf_flags);
@@ -1113,7 +1103,7 @@ static void __read(void *info)
curr_rq_lock_irq_save(&flags);
if (ctx->is_active)
- update_context_time(ctx, 1);
+ update_context_time(ctx);
counter->hw_ops->read(counter);
update_counter_times(counter);
curr_rq_unlock_irq_restore(&flags);
--
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