On 27/12/22 08:20, Longpeng(Mike) wrote:
From: Longpeng <longpeng2@huawei.com>
This allows the vhost-vdpa device to batch the setup of all its MRs of
host notifiers.
This significantly reduces the device starting time, e.g. the time spend
on setup the host notifier MRs reduce from 423ms to 32ms 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>
---
hw/virtio/vhost-vdpa.c | 25 +++++++++++++++++++------
1 file changed, 19 insertions(+), 6 deletions(-)
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index fd0c33b0e1..870265188a 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -512,9 +512,18 @@ static void vhost_vdpa_host_notifiers_uninit(struct
vhost_dev *dev, int n)
{
int i;
+ /*
+ * Pack all the changes to the memory regions in a single
+ * transaction to avoid a few updating of the address space
+ * topology.
+ */
+ memory_region_transaction_begin();
+
for (i = dev->vq_index; i < dev->vq_index + n; i++) {
vhost_vdpa_host_notifier_uninit(dev, i);
}
+
+ memory_region_transaction_commit();
}
Instead of optimizing one frontend, I wonder if we shouldn't expose
a 'bool memory_region_transaction_in_progress()' helper in memory.c,
and in virtio_queue_set_host_notifier_mr() backend, assert we are
within a transaction. That way we'd optimize all virtio frontends.