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vhost: allow device that does not depend on vhost worker

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vDPA device currently relays the eventfd via vhost worker. This is
inefficient due the latency of wakeup and scheduling, so this patch
tries to introduce a use_worker attribute for the vhost device. When
use_worker is not set with vhost_dev_init(), vhost won't try to
allocate a worker thread and the vhost_poll will be processed directly
in the wakeup function.

This help for vDPA since it reduces the latency caused by vhost worker.

In my testing, it saves 0.2 ms in pings between VMs on a mutual host.

Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20200529080303.15449-2-jasowang@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Jason Wang
2020-05-29 16:02:58 +08:00
committed by Michael S. Tsirkin
parent 5c1bd89b45
commit 01fcb1cbc8
6 changed files with 32 additions and 18 deletions
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2
drivers/vhost/net.c
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@@ -1326,7 +1326,7 @@ static int vhost_net_open(struct inode *inode, struct file *f)
}
vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX,
UIO_MAXIOV + VHOST_NET_BATCH,
VHOST_NET_PKT_WEIGHT, VHOST_NET_WEIGHT,
VHOST_NET_PKT_WEIGHT, VHOST_NET_WEIGHT, true,
NULL);
vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, EPOLLOUT, dev);