diff mbox series

[PULL,41/51] vhost: configure all host notifiers in a single MR transaction

Message ID 20230105091310.263867-42-mst@redhat.com
State New
Headers show
Series [PULL,01/51] virtio_net: Modify virtio_net_get_config to early return | expand

Commit Message

Michael S. Tsirkin Jan. 5, 2023, 9:16 a.m. UTC 
From: Longpeng <longpeng2@huawei.com>

This allows the vhost device to batch the setup of all its host notifiers.
This significantly reduces the device starting time, e.g. the time spend
on enabling notifiers reduce from 376ms to 9.1ms for a VM with 64 vCPUs
and 3 vhost-vDPA generic devices (vdpa_sim_blk, 64vq per device)

Signed-off-by: Longpeng <longpeng2@huawei.com>
Message-Id: <20221227072015.3134-3-longpeng2@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 hw/virtio/vhost.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
diff mbox series

Patch

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 87c49fa679..eb8c4c378c 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1562,16 +1562,25 @@  int vhost_dev_enable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev)
         return r;
     }
 
+    /*
+     * Batch all the host notifiers in a single transaction to avoid
+     * quadratic time complexity in address_space_update_ioeventfds().
+     */
+    memory_region_transaction_begin();
+
     for (i = 0; i < hdev->nvqs; ++i) {
         r = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), hdev->vq_index + i,
                                          true);
         if (r < 0) {
             error_report("vhost VQ %d notifier binding failed: %d", i, -r);
+            memory_region_transaction_commit();
             vhost_dev_disable_notifiers(hdev, vdev);
             return r;
         }
     }
 
+    memory_region_transaction_commit();
+
     return 0;
 }
 
@@ -1585,6 +1594,12 @@  void vhost_dev_disable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev)
     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
     int i, r;
 
+    /*
+     * Batch all the host notifiers in a single transaction to avoid
+     * quadratic time complexity in address_space_update_ioeventfds().
+     */
+    memory_region_transaction_begin();
+
     for (i = 0; i < hdev->nvqs; ++i) {
         r = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), hdev->vq_index + i,
                                          false);
@@ -1592,6 +1607,15 @@  void vhost_dev_disable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev)
             error_report("vhost VQ %d notifier cleanup failed: %d", i, -r);
         }
         assert (r >= 0);
+    }
+
+    /*
+     * The transaction expects the ioeventfds to be open when it
+     * commits. Do it now, before the cleanup loop.
+     */
+    memory_region_transaction_commit();
+
+    for (i = 0; i < hdev->nvqs; ++i) {
         virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), hdev->vq_index + i);
     }
     virtio_device_release_ioeventfd(vdev);