perf_counter: add more context information

Change the callchain context entries to u16, so as to gain some space.

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: <20090406094517.457320003@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index e22ab47..f9d5cf0 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -507,10 +507,10 @@
 extern void perf_counter_munmap(unsigned long addr, unsigned long len,
 				unsigned long pgoff, struct file *file);
 
-#define MAX_STACK_DEPTH		254
+#define MAX_STACK_DEPTH		255
 
 struct perf_callchain_entry {
-	u32	nr, hv, kernel, user;
+	u16	nr, hv, kernel, user;
 	u64	ip[MAX_STACK_DEPTH];
 };