>From 269442decf0f137cf7d09c32442fcd16dd319901 Mon Sep 17 00:00:00 2001 From: Anthony Liguori Date: Fri, 10 May 2013 13:43:11 -0500 Subject: [PATCH] qom: optimize casting to leaf class and parent class (v2) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Most QOM types use type_register_static but we still strdup the passed data. However, the original pointers are useful because GCC is pretty good about collapsing strings so its very likely any use of the pointer will end up being that same address. IOW, with a little trickery, we can compare types by just comparing strings and in fact that's what we do here. We do this for the two most common cases, casting to a leaf class or to the parent class. With these two changes, I see a decrease from around 2 hash table lookups to only a thousand with no run time lookups at all. Cc: Paolo Bonzini Cc: Aurelien Jarno Cc: Andreas Färber Reported-by: Aurelien Jarno Signed-off-by: Anthony Liguori --- v1 -> v2: - use strcmp() instead of == --- qom/object.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/qom/object.c b/qom/object.c index 75e6aac..99b5b33 100644 --- a/qom/object.c +++ b/qom/object.c @@ -132,7 +132,13 @@ TypeImpl *type_register(const TypeInfo *info) TypeImpl *type_register_static(const TypeInfo *info) { - return type_register(info); + TypeImpl *impl; + + impl = type_register(info); + impl->name = info->name; + impl->parent = info->parent; + + return impl; } static TypeImpl *type_get_by_name(const char *name) @@ -449,10 +455,17 @@ Object *object_dynamic_cast_assert(Object *obj, const char *typename) ObjectClass *object_class_dynamic_cast(ObjectClass *class, const char *typename) { - TypeImpl *target_type = type_get_by_name(typename); + TypeImpl *target_type; TypeImpl *type = class->type; ObjectClass *ret = NULL; + if (strcmp(type->name, typename) == 0 || + strcmp(type->parent, typename) == 0) { + return class; + } + + target_type = type_get_by_name(typename); + if (!target_type) { /* target class type unknown, so fail the cast */ return NULL; -- 1.8.0