On 07/25/2011 09:02 AM, Avi Kivity wrote:
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@xxxxxxxxxx>
What's the motivation for this? Was this just because it seemed neat to
do or did you run into a performance issue you were trying to solve?
---
memory.c | 20 ++++++++++++++++++++
memory.h | 8 ++++++++
2 files changed, 28 insertions(+), 0 deletions(-)
diff --git a/memory.c b/memory.c
index 009ad33..370e189 100644
--- a/memory.c
+++ b/memory.c
@@ -18,6 +18,8 @@
#include "kvm.h"
#include<assert.h>
+unsigned memory_region_transaction_depth = 0;
Shouldn't this be static?
Regards,
Anthony Liguori
+
typedef struct AddrRange AddrRange;
struct AddrRange {
@@ -623,6 +625,10 @@ 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);
}
@@ -631,6 +637,20 @@ 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
--
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