virtio-balloon: optimize the virtio-balloon on the ARM platform

Optimize the virtio-balloon feature on the ARM platform by adding
a variable to keep track of the current hot-plugged pc-dimm size,
instead of traversing the virtual machine's memory modules to count
the current RAM size during the balloon inflation or deflation
process. This variable can be updated only when plugging or unplugging
the device, which will result in an increase of approximately 60%
efficiency of balloon process on the ARM platform.

We tested the total amount of time required for the balloon inflation process on ARM:
inflate the balloon to 64GB of a 128GB guest under stress.
Before: 102 seconds
After: 42 seconds

Signed-off-by: Qi Xi <xiqi2@huawei.com>
Signed-off-by: Ming Yang yangming73@huawei.com
Message-Id: <e13bc78f96774bfab4576814c293aa52@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>

diff --git a/hw/mem/pc-dimm.c b/hw/mem/pc-dimm.c
index 50ef83215cc4535f2e6cc08b95be44471770c73f..37f1f4ccfd4bc8fb7a366a44bfb1c192e7d17ed9 100644 (file)
--- a/hw/mem/pc-dimm.c
+++ b/hw/mem/pc-dimm.c
@@ -81,6 +81,10 @@ void pc_dimm_plug(PCDIMMDevice *dimm, MachineState *machine)
 
     memory_device_plug(MEMORY_DEVICE(dimm), machine);
     vmstate_register_ram(vmstate_mr, DEVICE(dimm));
+    /* count only "real" DIMMs, not NVDIMMs */
+    if (!object_dynamic_cast(OBJECT(dimm), TYPE_NVDIMM)) {
+        machine->device_memory->dimm_size += memory_region_size(vmstate_mr);
+    }
 }
 
 void pc_dimm_unplug(PCDIMMDevice *dimm, MachineState *machine)
@@ -90,6 +94,9 @@ void pc_dimm_unplug(PCDIMMDevice *dimm, MachineState *machine)
 
     memory_device_unplug(MEMORY_DEVICE(dimm), machine);
     vmstate_unregister_ram(vmstate_mr, DEVICE(dimm));
+    if (!object_dynamic_cast(OBJECT(dimm), TYPE_NVDIMM)) {
+        machine->device_memory->dimm_size -= memory_region_size(vmstate_mr);
+    }
 }
 
 static int pc_dimm_slot2bitmap(Object *obj, void *opaque)

diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index 746f07c4d26fc5c1e3f95adcf40699ed1f2d7df3..2814a47cb1bca39d5bbd25f0a5f43dfdfd6b4223 100644 (file)
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -729,37 +729,14 @@ static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t *config_data)
     memcpy(config_data, &config, virtio_balloon_config_size(dev));
 }
 
-static int build_dimm_list(Object *obj, void *opaque)
-{
-    GSList **list = opaque;
-
-    if (object_dynamic_cast(obj, TYPE_PC_DIMM)) {
-        DeviceState *dev = DEVICE(obj);
-        if (dev->realized) { /* only realized DIMMs matter */
-            *list = g_slist_prepend(*list, dev);
-        }
-    }
-
-    object_child_foreach(obj, build_dimm_list, opaque);
-    return 0;
-}
-
 static ram_addr_t get_current_ram_size(void)
 {
-    GSList *list = NULL, *item;
-    ram_addr_t size = current_machine->ram_size;
-
-    build_dimm_list(qdev_get_machine(), &list);
-    for (item = list; item; item = g_slist_next(item)) {
-        Object *obj = OBJECT(item->data);
-        if (!strcmp(object_get_typename(obj), TYPE_PC_DIMM)) {
-            size += object_property_get_int(obj, PC_DIMM_SIZE_PROP,
-                                            &error_abort);
-        }
+    MachineState *machine = MACHINE(qdev_get_machine());
+    if (machine->device_memory) {
+        return machine->ram_size + machine->device_memory->dimm_size;
+    } else {
+        return machine->ram_size;
     }
-    g_slist_free(list);
-
-    return size;
 }
 
 static bool virtio_balloon_page_poison_support(void *opaque)

diff --git a/include/hw/boards.h b/include/hw/boards.h
index 6fbbfd56c8085365903ca1aaa350e3cabfc10400..f840f88d54e97035e18c44af81fbf70cb201b421 100644 (file)
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -292,10 +292,12 @@ struct MachineClass {
  * @base: address in guest physical address space where the memory
  * address space for memory devices starts
  * @mr: address space container for memory devices
+ * @dimm_size: the sum of plugged DIMMs' sizes
  */
 typedef struct DeviceMemoryState {
     hwaddr base;
     MemoryRegion mr;
+    uint64_t dimm_size;
 } DeviceMemoryState;
 
 /**