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Subject[tip:perfcounters/core] perf_counter: inheritable sample counters
Commit-ID:  2023b359214bbc5bad31571cf50d7fb83b535c0a
Gitweb: http://git.kernel.org/tip/2023b359214bbc5bad31571cf50d7fb83b535c0a
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Tue, 5 May 2009 17:50:26 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Tue, 5 May 2009 20:18:33 +0200

perf_counter: inheritable sample counters

Redirect the output to the parent counter and put in some sanity checks.

[ Impact: new perfcounter feature - inherited sampling counters ]

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090505155437.331556171@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
kernel/perf_counter.c | 32 ++++++++++++++++++++++++++++++--
1 files changed, 30 insertions(+), 2 deletions(-)
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index c881afe..60e55f0 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -738,10 +738,18 @@ static void perf_counter_enable(struct perf_counter *counter)
spin_unlock_irq(&ctx->lock);
}

-static void perf_counter_refresh(struct perf_counter *counter, int refresh)
+static int perf_counter_refresh(struct perf_counter *counter, int refresh)
{
+ /*
+ * not supported on inherited counters
+ */
+ if (counter->hw_event.inherit)
+ return -EINVAL;
+
atomic_add(refresh, &counter->event_limit);
perf_counter_enable(counter);
+
+ return 0;
}

/*
@@ -1307,7 +1315,7 @@ static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
perf_counter_disable_family(counter);
break;
case PERF_COUNTER_IOC_REFRESH:
- perf_counter_refresh(counter, arg);
+ err = perf_counter_refresh(counter, arg);
break;
case PERF_COUNTER_IOC_RESET:
perf_counter_reset(counter);
@@ -1814,6 +1822,12 @@ static int perf_output_begin(struct perf_output_handle *handle,
struct perf_mmap_data *data;
unsigned int offset, head;

+ /*
+ * For inherited counters we send all the output towards the parent.
+ */
+ if (counter->parent)
+ counter = counter->parent;
+
rcu_read_lock();
data = rcu_dereference(counter->data);
if (!data)
@@ -1995,6 +2009,9 @@ static void perf_counter_output(struct perf_counter *counter,
if (record_type & PERF_RECORD_ADDR)
perf_output_put(&handle, addr);

+ /*
+ * XXX PERF_RECORD_GROUP vs inherited counters seems difficult.
+ */
if (record_type & PERF_RECORD_GROUP) {
struct perf_counter *leader, *sub;
u64 nr = counter->nr_siblings;
@@ -2281,6 +2298,11 @@ int perf_counter_overflow(struct perf_counter *counter,
int events = atomic_read(&counter->event_limit);
int ret = 0;

+ /*
+ * XXX event_limit might not quite work as expected on inherited
+ * counters
+ */
+
counter->pending_kill = POLL_IN;
if (events && atomic_dec_and_test(&counter->event_limit)) {
ret = 1;
@@ -2801,6 +2823,12 @@ perf_counter_alloc(struct perf_counter_hw_event *hw_event,

pmu = NULL;

+ /*
+ * we currently do not support PERF_RECORD_GROUP on inherited counters
+ */
+ if (hw_event->inherit && (hw_event->record_type & PERF_RECORD_GROUP))
+ goto done;
+
if (perf_event_raw(hw_event)) {
pmu = hw_perf_counter_init(counter);
goto done;

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