On Thu, Mar 8, 2012 at 5:48 PM, George Bottas <gbottas@xxxxxxxxxxx> wrote: > I have a question regarding changing the queue size that is set in virtio_blk_init(). The current value is 128, which results in setting the queue depth in the Windows guest device to 8. Does anyone know if changing this value to defined maximum (1024) going to result in any issues? NB, we have also increased the thread pool accordingly. Our testing so far has produced a situation where initially we are seeing very high read request rates (1500+), and then at some point the reads from the Windows guest become serialized, i.e. the Windows guest synchronously sends one READ to the host, waits for it to complete, sends the next one, etc. Has this ever been seen anywhere else? > > Any help on this would be appreciated. If you are really limited to 8 requests then the issue is not the number of vring descriptors since recent virtio-blk has the indirect vring feature enabled. The indirect vring feature allows the guest to send 128 parallel requests - much higher than the 8 you mentioned from Windows. CCing Vadim who maintains the Windows virtio-blk driver. Stefan -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
