0b84103062
Ning Bo reported an abnormal 2-second gap when booting Kata container [1].
The unconditional timeout was caused by VSOCK_DEFAULT_CONNECT_TIMEOUT of
connecting from the client side. The vhost vsock client tries to connect
an initializing virtio vsock server.
The abnormal flow looks like:
host-userspace vhost vsock guest vsock
============== =========== ============
connect() --------> vhost_transport_send_pkt_work() initializing
| vq->private_data==NULL
| will not be queued
V
schedule_timeout(2s)
vhost_vsock_start() <--------- device ready
set vq->private_data
wait for 2s and failed
connect() again vq->private_data!=NULL recv connecting pkt
Details:
1. Host userspace sends a connect pkt, at that time, guest vsock is under
initializing, hence the vhost_vsock_start has not been called. So
vq->private_data==NULL, and the pkt is not been queued to send to guest
2. Then it sleeps for 2s
3. After guest vsock finishes initializing, vq->private_data is set
4. When host userspace wakes up after 2s, send connecting pkt again,
everything is fine.
As suggested by Stefano Garzarella, this fixes it by additional kicking the
send_pkt worker in vhost_vsock_start once the virtio device is started. This
makes the pending pkt sent again.
After this patch, kata-runtime (with vsock enabled) boot time is reduced
from 3s to 1s on a ThunderX2 arm64 server.
[1] https://github.com/kata-containers/runtime/issues/1917
Reported-by: Ning Bo <n.b@live.com>
Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Jia He <justin.he@arm.com>
Link: https://lore.kernel.org/r/20200501043840.186557-1-justin.he@arm.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.