x86: Add NMI duration tracepoints
This patch has been invaluable in my adventures finding
issues in the perf NMI handler. I'm as big a fan of
printk() as anybody is, but using printk() in NMIs is
deadly when they're happening frequently.
Even hacking in trace_printk() ended up eating enough
CPU to throw off some of the measurements I was making.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: paulus@samba.org
Cc: acme@ghostprotocols.net
Cc: Dave Hansen <dave@sr71.net>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index e9bae4c..0920212 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -30,6 +30,9 @@
#include <asm/nmi.h>
#include <asm/x86_init.h>
+#define CREATE_TRACE_POINTS
+#include <trace/events/nmi.h>
+
struct nmi_desc {
spinlock_t lock;
struct list_head head;
@@ -108,11 +111,13 @@
*/
list_for_each_entry_rcu(a, &desc->head, list) {
u64 before, delta, whole_msecs;
- int decimal_msecs;
+ int decimal_msecs, thishandled;
before = local_clock();
- handled += a->handler(type, regs);
+ thishandled = a->handler(type, regs);
+ handled += thishandled;
delta = local_clock() - before;
+ trace_nmi_handler(a->handler, (int)delta, thishandled);
if (delta < nmi_longest_ns)
continue;
