On 12/16/21 2:08 AM, Christoph Hellwig wrote:

On Wed, Dec 15, 2021 at 09:24:21AM -0700, Jens Axboe wrote:

quoted

+	spin_lock(&nvmeq->sq_lock);
+	while (!rq_list_empty(*rqlist)) {
+		struct request *req = rq_list_pop(rqlist);
+		struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
+
+		memcpy(nvmeq->sq_cmds + (nvmeq->sq_tail << nvmeq->sqes),
+				absolute_pointer(&iod->cmd), sizeof(iod->cmd));
+		if (++nvmeq->sq_tail == nvmeq->q_depth)
+			nvmeq->sq_tail = 0;

So this doesn't even use the new helper added in patch 2?  I think this
should call nvme_sq_copy_cmd().

But you NAK'ed that one? It definitely should use that helper, so I take it
you are fine with it then if we do it here too? That would make 3 call sites,
and I still do think the helper makes sense...

The rest looks identical to the incremental patch I posted, so I guess
the performance degration measured on the first try was a measurement
error?

It may have been a measurement error, I'm honestly not quite sure. I
reshuffled and modified a few bits here and there, and verified the
end result. Wish I had a better answer, but...

-- 
Jens Axboe