memory: transaction API
Allow changes to the memory hierarchy to be accumulated and
made visible all at once. This reduces computational effort,
especially when an accelerator (e.g. kvm) is involved.
Useful when a single register update causes multiple changes
to an address space.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/memory.c b/memory.c
index 7a5670e..5c6e63d 100644
--- a/memory.c
+++ b/memory.c
@@ -18,6 +18,8 @@
#include "kvm.h"
#include <assert.h>
+unsigned memory_region_transaction_depth = 0;
+
typedef struct AddrRange AddrRange;
struct AddrRange {
@@ -626,6 +628,10 @@
static void memory_region_update_topology(void)
{
+ if (memory_region_transaction_depth) {
+ return;
+ }
+
if (address_space_memory.root) {
address_space_update_topology(&address_space_memory);
}
@@ -634,6 +640,18 @@
}
}
+void memory_region_transaction_begin(void)
+{
+ ++memory_region_transaction_depth;
+}
+
+void memory_region_transaction_commit(void)
+{
+ assert(memory_region_transaction_depth);
+ --memory_region_transaction_depth;
+ memory_region_update_topology();
+}
+
void memory_region_init(MemoryRegion *mr,
const char *name,
uint64_t size)
diff --git a/memory.h b/memory.h
index c280a39..4e518b2 100644
--- a/memory.h
+++ b/memory.h
@@ -456,6 +456,14 @@
void memory_region_del_subregion(MemoryRegion *mr,
MemoryRegion *subregion);
+/* Start a transaction; changes will be accumulated and made visible only
+ * when the transaction ends.
+ */
+void memory_region_transaction_begin(void);
+/* Commit a transaction and make changes visible to the guest.
+ */
+void memory_region_transaction_commit(void);
+
#endif
#endif
