[PATCH v5 04/16] perf kvm: Use subtraction for comparison metrics

[Leo Yan]

Currently the metrics comparison uses greater operator (>), it returns
the boolean value (0 or 1).

This patch changes to use subtraction as comparison result, which can
be used by histograms sorting.  Since the subtraction result is u64
type, we change key_cmp_fun's return type to int64_t to avoid overflow.

Signed-off-by: Leo Yan <leo.yan at linaro.org>
---
 tools/perf/builtin-kvm.c   | 6 +++---
 tools/perf/util/kvm-stat.h | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
index 62c097a37da9..4e9519390da6 100644
--- a/tools/perf/builtin-kvm.c
+++ b/tools/perf/builtin-kvm.c
@@ -63,10 +63,10 @@ static u64 get_event_ ##func(struct kvm_event *event, int vcpu)		\
 
 #define COMPARE_EVENT_KEY(func, field)					\
 GET_EVENT_KEY(func, field)						\
-static int cmp_event_ ## func(struct kvm_event *one,			\
+static int64_t cmp_event_ ## func(struct kvm_event *one,		\
 			      struct kvm_event *two, int vcpu)		\
 {									\
-	return get_event_ ##func(one, vcpu) >				\
+	return get_event_ ##func(one, vcpu) -				\
 	       get_event_ ##func(two, vcpu);				\
 }
 
@@ -523,7 +523,7 @@ static void insert_to_result(struct rb_root *result, struct kvm_event *event,
 		p = container_of(*rb, struct kvm_event, rb);
 		parent = *rb;
 
-		if (bigger(event, p, vcpu))
+		if (bigger(event, p, vcpu) > 0)
 			rb = &(*rb)->rb_left;
 		else
 			rb = &(*rb)->rb_right;
diff --git a/tools/perf/util/kvm-stat.h b/tools/perf/util/kvm-stat.h
index 40a4b66cfee6..0c2400d9b227 100644
--- a/tools/perf/util/kvm-stat.h
+++ b/tools/perf/util/kvm-stat.h
@@ -40,7 +40,7 @@ struct kvm_event {
 	struct kvm_event_stats *vcpu;
 };
 
-typedef int (*key_cmp_fun)(struct kvm_event*, struct kvm_event*, int);
+typedef int64_t (*key_cmp_fun)(struct kvm_event*, struct kvm_event*, int);
 
 struct kvm_event_key {
 	const char *name;
-- 
2.34.1