On 27/07/2017 04:36, Jay Zhou wrote:
Qemu_savevm_state_cleanup takes about 300ms in my ram migration tests
with a 8U24G vm(20G is really occupied), the main cost comes from
KVM_SET_USER_MEMORY_REGION ioctl when mem.memory_size = 0 in
kvm_set_user_memory_region. In kmod, the main cost is
kvm_zap_obsolete_pages, which traverses the active_mmu_pages list to
zap the unsync sptes.
It can be optimized by delaying memory_global_dirty_log_stop to the next
vm_start.
Changes v1->v2:
- create a VMChangeStateHandler in memory.c to reduce the coupling [Paolo]
Signed-off-by: Jay Zhou <address@hidden>
memory_vm_change_state_handler should delete the handler.
Apart from that, because there is no protection against nested
invocations of memory_global_dirty_log_start/stop, a little more work is
needed.
---
memory.c | 27 ++++++++++++++++++++++++++-
1 file changed, 26 insertions(+), 1 deletion(-)
diff --git a/memory.c b/memory.c
index a7bc70a..4c22b7e 100644
--- a/memory.c
+++ b/memory.c
@@ -2357,8 +2357,14 @@ void memory_global_dirty_log_sync(void)
}
}
+static VMChangeStateEntry *vmstate_change;
+
void memory_global_dirty_log_start(void)
{
+ if (vmstate_change) {
+ qemu_del_vm_change_state_handler(vmstate_change);
This should also NULL vmstate_change, so that you can detect the case
where the handler is already installed.
+ }
+
global_dirty_log = true;
MEMORY_LISTENER_CALL_GLOBAL(log_global_start, Forward);
@@ -2369,7 +2375,7 @@ void memory_global_dirty_log_start(void)
memory_region_transaction_commit();
}
-void memory_global_dirty_log_stop(void)
+static void memory_global_dirty_log_do_stop(void)
{
global_dirty_log = false;
@@ -2381,6 +2387,25 @@ void memory_global_dirty_log_stop(void)
MEMORY_LISTENER_CALL_GLOBAL(log_global_stop, Reverse);
}
+static void memory_vm_change_state_handler(void *opaque, int running,
+ RunState state)
+{
+ if (running) {
+ memory_global_dirty_log_do_stop();
Because this will delete the handler, it should also NULL vmstate_change.
+ }
+}
+
+void memory_global_dirty_log_stop(void)
+{
+ if (!runstate_is_running()) {
+ vmstate_change = qemu_add_vm_change_state_handler(
+ memory_vm_change_state_handler, NULL);
And this needs to exit immediately if you have an installed handler.
Thanks,
Paolo
+ return;
+ }
+
+ memory_global_dirty_log_do_stop();
+}
+
static void listener_add_address_space(MemoryListener *listener,
AddressSpace *as)
{
.