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authorPaolo Bonzini <pbonzini@redhat.com>2015-12-09 11:44:25 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2015-12-17 17:33:48 +0100
commit612263cf33062f7441a5d0e3b37c65991fdc3210 (patch)
treeb2f6e1e60a93546ac7e96647b67b113b102841fb /memory.c
parenta676854f3447019c7c4b005ab6aece905fccfddd (diff)
downloadqemu-arm-612263cf33062f7441a5d0e3b37c65991fdc3210.tar.gz
memory: avoid unnecessary object_ref/unref
For the common case of DMA into non-hotplugged RAM, it is unnecessary but expensive to do object_ref/unref. Add back an owner field to MemoryRegion, so that these memory regions can skip the reference counting. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'memory.c')
-rw-r--r--memory.c28
1 files changed, 12 insertions, 16 deletions
diff --git a/memory.c b/memory.c
index f666c77823..b4d2b52a77 100644
--- a/memory.c
+++ b/memory.c
@@ -905,20 +905,22 @@ void memory_region_init(MemoryRegion *mr,
const char *name,
uint64_t size)
{
- if (!owner) {
- owner = container_get(qdev_get_machine(), "/unattached");
- }
-
object_initialize(mr, sizeof(*mr), TYPE_MEMORY_REGION);
mr->size = int128_make64(size);
if (size == UINT64_MAX) {
mr->size = int128_2_64();
}
mr->name = g_strdup(name);
+ mr->owner = owner;
if (name) {
char *escaped_name = memory_region_escape_name(name);
char *name_array = g_strdup_printf("%s[*]", escaped_name);
+
+ if (!owner) {
+ owner = container_get(qdev_get_machine(), "/unattached");
+ }
+
object_property_add_child(owner, name_array, OBJECT(mr), &error_abort);
object_unref(OBJECT(mr));
g_free(name_array);
@@ -1369,24 +1371,18 @@ void memory_region_ref(MemoryRegion *mr)
* The memory region is a child of its owner. As long as the
* owner doesn't call unparent itself on the memory region,
* ref-ing the owner will also keep the memory region alive.
- * Memory regions without an owner are supposed to never go away,
- * but we still ref/unref them for debugging purposes.
+ * Memory regions without an owner are supposed to never go away;
+ * we do not ref/unref them because it slows down DMA sensibly.
*/
- Object *obj = OBJECT(mr);
- if (obj && obj->parent) {
- object_ref(obj->parent);
- } else {
- object_ref(obj);
+ if (mr && mr->owner) {
+ object_ref(mr->owner);
}
}
void memory_region_unref(MemoryRegion *mr)
{
- Object *obj = OBJECT(mr);
- if (obj && obj->parent) {
- object_unref(obj->parent);
- } else {
- object_unref(obj);
+ if (mr && mr->owner) {
+ object_unref(mr->owner);
}
}