On Thu, Mar 8, 2012 at 5:48 PM, George Bottas <[email protected]> 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 [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
