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>

1 files changed, 30 insertions, 2 deletions

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index c881afef997b..60e55f0b48f4 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;