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[Qemu-devel] [PATCH for-1.5 1/2] qom: aggressively optimize qom casting
From: |
Anthony Liguori |
Subject: |
[Qemu-devel] [PATCH for-1.5 1/2] qom: aggressively optimize qom casting |
Date: |
Mon, 13 May 2013 15:31:45 -0500 |
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 <address@hidden>
---
include/qom/object.h | 4 ++++
qom/object.c | 40 ++++++++++++++++++++++++++++++++++++++--
2 files changed, 42 insertions(+), 2 deletions(-)
diff --git a/include/qom/object.h b/include/qom/object.h
index 63e2a40..23fc048 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -344,6 +344,8 @@ typedef void (ObjectUnparent)(Object *obj);
*/
typedef void (ObjectFree)(void *obj);
+#define OBJECT_CLASS_CAST_CACHE 4
+
/**
* ObjectClass:
*
@@ -356,6 +358,8 @@ struct ObjectClass
Type type;
GSList *interfaces;
+ const char *cast_cache[OBJECT_CLASS_CAST_CACHE];
+
ObjectUnparent *unparent;
};
diff --git a/qom/object.c b/qom/object.c
index f5f416b..ec88231 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;
}
--
1.8.0
- [Qemu-devel] [PATCH for-1.5 1/2] qom: aggressively optimize qom casting,
Anthony Liguori <=