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migration: optimize the downtime
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 v2->v3: - NULL VMChangeStateHandler if it is deleted and protect the scenario of nested invocations of memory_global_dirty_log_start/stop [Paolo] Changes v1->v2: - create a VMChangeStateHandler in memory.c to reduce the coupling [Paolo] Signed-off-by: Jay Zhou <jianjay.zhou@huawei.com> Message-Id: <1501237733-2736-1-git-send-email-jianjay.zhou@huawei.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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8bfce83a3b
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1931076077
36
memory.c
36
memory.c
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@ -2357,8 +2357,15 @@ void memory_global_dirty_log_sync(void)
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}
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}
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static VMChangeStateEntry *vmstate_change;
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void memory_global_dirty_log_start(void)
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{
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if (vmstate_change) {
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qemu_del_vm_change_state_handler(vmstate_change);
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vmstate_change = NULL;
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}
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global_dirty_log = true;
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MEMORY_LISTENER_CALL_GLOBAL(log_global_start, Forward);
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@ -2369,7 +2376,7 @@ void memory_global_dirty_log_start(void)
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memory_region_transaction_commit();
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}
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void memory_global_dirty_log_stop(void)
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static void memory_global_dirty_log_do_stop(void)
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{
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global_dirty_log = false;
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@ -2381,6 +2388,33 @@ void memory_global_dirty_log_stop(void)
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MEMORY_LISTENER_CALL_GLOBAL(log_global_stop, Reverse);
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}
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static void memory_vm_change_state_handler(void *opaque, int running,
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RunState state)
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{
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if (running) {
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memory_global_dirty_log_do_stop();
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if (vmstate_change) {
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qemu_del_vm_change_state_handler(vmstate_change);
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vmstate_change = NULL;
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}
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}
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}
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void memory_global_dirty_log_stop(void)
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{
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if (!runstate_is_running()) {
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if (vmstate_change) {
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return;
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}
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vmstate_change = qemu_add_vm_change_state_handler(
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memory_vm_change_state_handler, NULL);
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return;
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}
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memory_global_dirty_log_do_stop();
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}
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static void listener_add_address_space(MemoryListener *listener,
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AddressSpace *as)
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{
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