perf_counter: add PERF_RECORD_CPU

Allow recording the CPU number the event was generated on.

RFC: this leaves a u32 as reserved, should we fill in the
     node_id() there, or leave this open for future extention,
     as userspace can already easily do the cpu->node mapping
     if needed.

[ Impact: extend perfcounter output record format ]
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: <20090508170029.008627711@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/perf_counter.h

@@ -105,6 +105,7 @@ enum perf_counter_record_format {
 	PERF_RECORD_GROUP	= 1U << 4,
 	PERF_RECORD_CALLCHAIN	= 1U << 5,
 	PERF_RECORD_CONFIG	= 1U << 6,
+	PERF_RECORD_CPU		= 1U << 7,
 };
 
 /*
@@ -260,6 +261,7 @@ enum perf_event_type {
 	 * 	{ u64			time;     } && PERF_RECORD_TIME
 	 * 	{ u64			addr;     } && PERF_RECORD_ADDR
 	 * 	{ u64			config;   } && PERF_RECORD_CONFIG
+	 * 	{ u32			cpu, res; } && PERF_RECORD_CPU
 	 *
 	 * 	{ u64			nr;
 	 * 	  { u64 event, val; } 	cnt[nr];  } && PERF_RECORD_GROUP

kernel/perf_counter.c

@@ -1956,6 +1956,9 @@ static void perf_counter_output(struct perf_counter *counter,
 	struct perf_callchain_entry *callchain = NULL;
 	int callchain_size = 0;
 	u64 time;
+	struct {
+		u32 cpu, reserved;
+	} cpu_entry;
 
 	header.type = 0;
 	header.size = sizeof(header);
@@ -1999,6 +2002,13 @@ static void perf_counter_output(struct perf_counter *counter,
 		header.size += sizeof(u64);
 	}
 
+	if (record_type & PERF_RECORD_CPU) {
+		header.type |= PERF_RECORD_CPU;
+		header.size += sizeof(cpu_entry);
+
+		cpu_entry.cpu = raw_smp_processor_id();
+	}
+
 	if (record_type & PERF_RECORD_GROUP) {
 		header.type |= PERF_RECORD_GROUP;
 		header.size += sizeof(u64) +
@@ -2037,6 +2047,9 @@ static void perf_counter_output(struct perf_counter *counter,
 	if (record_type & PERF_RECORD_CONFIG)
 		perf_output_put(&handle, counter->hw_event.config);
 
+	if (record_type & PERF_RECORD_CPU)
+		perf_output_put(&handle, cpu_entry);
+
 	/*
 	 * XXX PERF_RECORD_GROUP vs inherited counters seems difficult.
 	 */