[PATCH] memory: transaction API

Avi Kivity
2011-07-21T10:21:25Z

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>
---
memory.c | 20 ++++++++++++++++++++
memory.h | 8 ++++++++
2 files changed, 28 insertions(+), 0 deletions(-)

diff --git a/memory.c b/memory.c
index 0ffc905..8780533 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 {
@@ -648,6 +650,10 @@ static void address_space_update_topology(AddressSpace *as)

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);
}
@@ -656,6 +662,20 @@ static void memory_region_update_topology(void)
}
}

+void memory_region_transaction_begin(void)
+{
+ ++memory_region_transaction_depth;
+}
+
+void memory_region_transaction_commit(void)
+{
+ if (!memory_region_transaction_depth) {
+ abort();
+ }
+ --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 e4c0ad1..cb3a9b6 100644
--- a/memory.h
+++ b/memory.h
@@ -246,6 +246,14 @@ void memory_region_add_subregion_overlap(MemoryRegion *mr,
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
--
1.7.5.3