On 4/10/23 01:32, Damien Le Moal wrote:
On 4/8/23 08:58, Bart Van Assche wrote:
@@ -834,7 +847,18 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
* set expire time and add to fifo list
*/
rq->fifo_time = jiffies + dd->fifo_expire[data_dir];
- list_add_tail(&rq->queuelist, &per_prio->fifo_list[data_dir]);
+ insert_before = &per_prio->fifo_list[data_dir];
+ if (blk_rq_is_seq_zoned_write(rq)) {
+ const unsigned int zno = blk_rq_zone_no(rq);
+ struct request *rq2 = rq;
+
+ while ((rq2 = deadline_earlier_request(rq2)) &&
+ blk_rq_zone_no(rq2) == zno &&
+ blk_rq_pos(rq2) > blk_rq_pos(rq)) {
+ insert_before = &rq2->queuelist;
+ }
+ }
+ list_add_tail(&rq->queuelist, insert_before);
This seems incorrect: the fifo list is ordered in arrival time, so always
queuing at the tail is the right thing to do. What I think you want to do here
is when we choose the next request to be the oldest (to implement aging), you
want to get the first request for the target zone of that oldest request. But
why do that on insert ? This should be in the dispatch code, coded in
deadline_fifo_request(), no ?
Hi Damien,
If the dispatch code would have to look up the zoned write with the
lowest LBA then it would have to iterate over the entire FIFO list. The
above loop will on average perform much less work. If no requeuing
happens, the expression 'blk_rq_pos(rq2) > blk_rq_pos(rq)' will evaluate
to false the first time it is evaluated and the loop body will never be
executed.
Thanks,
Bart.
