util: adjust coroutine pool size to virtio block queue

util: adjust coroutine pool size to virtio block queue

Coroutine pool size was 64 from long ago, and the basis was organized in the commit message in 4d68e86b.

At that time, virtio-blk queue-size and num-queue were not configuable, and equivalent values were 128 and 1.

Coroutine pool size 64 was fine then.

Later queue-size and num-queue got configuable, and default values were increased.

Coroutine pool with size 64 exhausts frequently with random disk IO in new size, and slows down.

This commit adjusts coroutine pool size adaptively with new values.

This commit adds 64 by default, but now coroutine is not only for block devices,

and is not too much burdon comparing with new default.

pool size of 128 * vCPUs.

Signed-off-by: Hiroki Narukawa <hnarukaw@yahoo-corp.jp>
Message-id: 20220214115302.13294-2-hnarukaw@yahoo-corp.jp
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>