perf_counter: optionally provide the pid/tid of the sampled task

Allow cpu wide counters to profile userspace by providing what process
the sample belongs to.

This raises the first issue with the output type, lots of these
options: group, tid, callchain, etc.. are non-exclusive and could be
combined, suggesting a bitfield.

However, things like the mmap() data stream doesn't fit in that.

How to split the type field...

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Orig-LKML-Reference: <20090325113317.013775235@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 16 insertions, 2 deletions

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 7669afe82cc7..f3e1b27bc1b8 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1528,16 +1528,30 @@ out:
 static void perf_output_simple(struct perf_counter *counter,
                                int nmi, struct pt_regs *regs)
 {
+        unsigned int size;
         struct {
                 struct perf_event_header header;
                 u64 ip;
+                u32 pid, tid;
         } event;
 
         event.header.type = PERF_EVENT_IP;
-        event.header.size = sizeof(event);
         event.ip = instruction_pointer(regs);
 
-        perf_output_write(counter, nmi, &event, sizeof(event));
+        size = sizeof(event);
+
+        if (counter->hw_event.include_tid) {
+                /* namespace issues */
+                event.pid = current->group_leader->pid;
+                event.tid = current->pid;
+
+                event.header.type |= __PERF_EVENT_TID;
+        } else
+                size -= sizeof(u64);
+
+        event.header.size = size;
+
+        perf_output_write(counter, nmi, &event, size);
 }
 
 static void perf_output_group(struct perf_counter *counter, int nmi)