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memory: optimize empty transactions due to mutators 

The mutating memory APIs can easily cause empty transactions,
where the mutators don't actually change anything, or perhaps
only modify disabled regions.  Detect these conditions and
avoid regenerating the memory topology.

Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Avi Kivity 2011-09-14 12:16:20 +03:00
parent 4703359e0e
commit e87c099f1c
1 changed files with 7 additions and 1 deletions
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8
memory.c
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@ -19,6 +19,7 @@
#include <assert.h>
unsigned memory_region_transaction_depth = 0;
static bool memory_region_update_pending = false;
typedef struct AddrRange AddrRange;
@ -757,6 +758,7 @@ static void address_space_update_topology(AddressSpace *as)
static void memory_region_update_topology(MemoryRegion *mr)
{
if (memory_region_transaction_depth) {
memory_region_update_pending |= !mr || mr->enabled;
return;
}
@ -770,6 +772,8 @@ static void memory_region_update_topology(MemoryRegion *mr)
if (address_space_io.root) {
address_space_update_topology(&address_space_io);
}
memory_region_update_pending = false;
}
void memory_region_transaction_begin(void)
@ -781,7 +785,9 @@ void memory_region_transaction_commit(void)
{
assert(memory_region_transaction_depth);
--memory_region_transaction_depth;
memory_region_update_topology(NULL);
if (!memory_region_transaction_depth && memory_region_update_pending) {
memory_region_update_topology(NULL);
}
}
static void memory_region_destructor_none(MemoryRegion *mr)