On 11/28/18 12:26 AM, Christoph Hellwig wrote:
>> + } else if (plug && q->mq_ops->commit_rqs) {
>> + /*
>> + * If we have a ->commit_rqs(), then we know the driver can
>> + * batch submission doorbell updates. Add rq to plug list,
>> + * and flush if we exceed the plug count only.
>> + */
>> + blk_mq_bio_to_request(rq, bio);
>> + blk_mq_put_ctx(data.ctx);
>> +
>> + /*
>> + * If we have requests for more than one queue here, we
>> + * should sort the list when it's flushed.
>> + */
>> + if (!plug->do_sort && !list_empty(&plug->mq_list)) {
>> + same_queue_rq = list_first_entry(&plug->mq_list,
>> + struct request, queuelist);
>> + if (same_queue_rq->q != q)
>> + plug->do_sort = true;
>> + }
>> +
>> + list_add_tail(&rq->queuelist, &plug->mq_list);
>> + plug->rq_count++;
>> + if (plug->rq_count >= BLK_MAX_REQUEST_COUNT) {
>> + blk_flush_plug_list(plug, false);
>> + trace_block_plug(q);
>> + }
>
> This seems like a slight variation of the the single queue plug
> case. Can we share the code instead of having slightly differing
> logic?
I'll see if I can fold them.
> Also that should this respect blk_queue_nomerges?
It doesn't do any merging at all, it's just batching for the list
inserts. In terms of plug merging, if nomerges isn't true, then we would
have done that further up.
--
Jens Axboe
