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authorAnthony Liguori <aliguori@us.ibm.com>2013-05-13 15:22:24 -0500
committerAnthony Liguori <aliguori@us.ibm.com>2013-05-13 15:27:18 -0500
commit035873283b3f7514ad77d409870ccfd5f9680d9e (patch)
treec7b21f32c53e37dc7da2030debe1ecbaae98384a /qom
parentb087143b4d010451208264b7c841436aafe1cbb1 (diff)
qom: aggressively optimize qom casting
This patch adds a small typename cache to ObjectClass. This allows caching positive casts within each ObjectClass. Benchmarking a PPC workload provided by Aurelien, this patch eliminates every single g_hash_table_lookup() happening during the benchmark (which was about 2 million per-second). With this patch applied, I get exactly the same performance (within the margin of error) as with --disable-qom-cast-debug. N.B. it's safe to cache typenames only from the _assert() macros because they are always called with string literals. Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Diffstat (limited to 'qom')
-rw-r--r--qom/object.c40
1 files changed, 38 insertions, 2 deletions
diff --git a/qom/object.c b/qom/object.c
index f5f416bc81..ec88231fa9 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -439,7 +439,16 @@ Object *object_dynamic_cast_assert(Object *obj, const char *typename,
typename, file, line, func);
#ifdef CONFIG_QOM_CAST_DEBUG
- Object *inst = object_dynamic_cast(obj, typename);
+ int i;
+ Object *inst;
+
+ for (i = 0; i < OBJECT_CLASS_CAST_CACHE; i++) {
+ if (obj->class->cast_cache[i] == typename) {
+ goto out;
+ }
+ }
+
+ inst = object_dynamic_cast(obj, typename);
if (!inst && obj) {
fprintf(stderr, "%s:%d:%s: Object %p is not an instance of type %s\n",
@@ -448,6 +457,15 @@ Object *object_dynamic_cast_assert(Object *obj, const char *typename,
}
assert(obj == inst);
+
+ if (obj == inst) {
+ for (i = 1; i < OBJECT_CLASS_CAST_CACHE; i++) {
+ obj->class->cast_cache[i - 1] = obj->class->cast_cache[i];
+ }
+ obj->class->cast_cache[i - 1] = typename;
+ }
+
+out:
#endif
return obj;
}
@@ -510,7 +528,16 @@ ObjectClass *object_class_dynamic_cast_assert(ObjectClass *class,
trace_object_class_dynamic_cast_assert(class ? class->type->name : "(null)",
typename, file, line, func);
-#ifndef CONFIG_QOM_CAST_DEBUG
+#ifdef CONFIG_QOM_CAST_DEBUG
+ int i;
+
+ for (i = 0; i < OBJECT_CLASS_CAST_CACHE; i++) {
+ if (class->cast_cache[i] == typename) {
+ ret = class;
+ goto out;
+ }
+ }
+#else
if (!class->interfaces) {
return class;
}
@@ -523,6 +550,15 @@ ObjectClass *object_class_dynamic_cast_assert(ObjectClass *class,
abort();
}
+#ifdef CONFIG_QOM_CAST_DEBUG
+ if (ret == class) {
+ for (i = 1; i < OBJECT_CLASS_CAST_CACHE; i++) {
+ class->cast_cache[i - 1] = class->cast_cache[i];
+ }
+ class->cast_cache[i - 1] = typename;
+ }
+out:
+#endif
return ret;
}