On Thu, Nov 29, 2018 at 01:19:14PM -0700, Keith Busch wrote:

On Thu, Nov 29, 2018 at 08:12:58PM +0100, Christoph Hellwig wrote:

quoted

+enum hctx_type {
+	HCTX_TYPE_DEFAULT,	/* all I/O not otherwise accounted for */
+	HCTX_TYPE_READ,		/* just for READ I/O */
+	HCTX_TYPE_POLL,		/* polled I/O of any kind */
+
+	HCTX_MAX_TYPES,
 };

Well, there goes my plan to use this with Weighted-Round-Robin NVMe IO
queues!

Wo between what do you even want to round robin?  If it is between
reads and writes that's easy.  If we want priority reads or writes
(separate from polling) that's also still fairly easily.

Btw, one thing I wanted to try once I get hold of the right hardware
is to mark the poll queues as priority queues and see if that makes
any differents in poll IOPS/latency.