diff mbox series

[QEMU,v2,3/3] vhost-user-blk-pci: introduce auto-num-queues property

Message ID 169165122958.4096.6557269987206106594-3@git.sr.ht
State New
Headers show
Series [QEMU,v2,1/3] virtio-scsi-pci: introduce auto-num-queues property | expand

Commit Message

~hyman Aug. 5, 2023, 12:39 a.m. UTC 
From: Hyman Huang(黄勇) <yong.huang@smartx.com>

Commit "a4eef0711b vhost-user-blk-pci: default num_queues to -smp N"
implment sizing the number of vhost-user-blk-pci request virtqueues
to match the number of vCPUs automatically. Which improves IO
preformance remarkably.

To enable this feature for the existing VMs, the cloud platform
may migrate VMs from the source hypervisor (num_queues is set to
1 by default) to the destination hypervisor (num_queues is set to
-smp N) lively. The different num-queues for vhost-user-blk-pci
devices between the source side and the destination side will
result in migration failure due to loading vmstate incorrectly
on the destination side.

To provide a smooth upgrade solution, introduce the
auto-num-queues property for the vhost-user-blk-pci device. This
allows upper APPs, e.g., libvirt, to recognize the hypervisor's
capability of allocating the virtqueues automatically by probing
the vhost-user-blk-pci.auto-num-queues property. Basing on which,
upper APPs can ensure to allocate the same num-queues on the
destination side in case of migration failure.

Signed-off-by: Hyman Huang(黄勇) <yong.huang@smartx.com>
---
 hw/block/vhost-user-blk.c          | 1 +
 hw/virtio/vhost-user-blk-pci.c     | 9 ++++++++-
 include/hw/virtio/vhost-user-blk.h | 5 +++++
 3 files changed, 14 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index eecf3f7a81..34e23b1727 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -566,6 +566,7 @@  static const VMStateDescription vmstate_vhost_user_blk = {
 
 static Property vhost_user_blk_properties[] = {
     DEFINE_PROP_CHR("chardev", VHostUserBlk, chardev),
+    DEFINE_PROP_BOOL("auto-num-queues", VHostUserBlk, auto_num_queues, true),
     DEFINE_PROP_UINT16("num-queues", VHostUserBlk, num_queues,
                        VHOST_USER_BLK_AUTO_NUM_QUEUES),
     DEFINE_PROP_UINT32("queue-size", VHostUserBlk, queue_size, 128),
diff --git a/hw/virtio/vhost-user-blk-pci.c b/hw/virtio/vhost-user-blk-pci.c
index eef8641a98..f7776e928a 100644
--- a/hw/virtio/vhost-user-blk-pci.c
+++ b/hw/virtio/vhost-user-blk-pci.c
@@ -56,7 +56,14 @@  static void vhost_user_blk_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
     DeviceState *vdev = DEVICE(&dev->vdev);
 
     if (dev->vdev.num_queues == VHOST_USER_BLK_AUTO_NUM_QUEUES) {
-        dev->vdev.num_queues = virtio_pci_optimal_num_queues(0);
+        /*
+         * Allocate virtqueues automatically only if auto_num_queues
+         * property set true.
+         */
+        if (dev->vdev.auto_num_queues)
+            dev->vdev.num_queues = virtio_pci_optimal_num_queues(0);
+        else
+            dev->vdev.num_queues = 1;
     }
 
     if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
diff --git a/include/hw/virtio/vhost-user-blk.h b/include/hw/virtio/vhost-user-blk.h
index ea085ee1ed..e6f0515bc6 100644
--- a/include/hw/virtio/vhost-user-blk.h
+++ b/include/hw/virtio/vhost-user-blk.h
@@ -50,6 +50,11 @@  struct VHostUserBlk {
     bool connected;
     /* vhost_user_blk_start/vhost_user_blk_stop */
     bool started_vu;
+    /*
+     * Set to true if virtqueues allow to be allocated to
+     * match the number of virtual CPUs automatically.
+     */
+    bool auto_num_queues;
 };
 
 #endif