diff mbox

blk-mq: Explain when 'active_queues' is decremented

Message ID 20180110163333.14345-1-bart.vanassche@wdc.com (mailing list archive)
State New, archived
Headers show

Commit Message

Bart Van Assche Jan. 10, 2018, 4:33 p.m. UTC 
It is nontrivial to derive from the blk-mq source code when
blk_mq_tags.active_queues is decremented. Hence add a comment that
explains this.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
---
 block/blk-mq.c | 6 ++++++
 1 file changed, 6 insertions(+)

Comments

Jens Axboe Jan. 10, 2018, 4:45 p.m. UTC | #1 
On 1/10/18 9:33 AM, Bart Van Assche wrote:
> It is nontrivial to derive from the blk-mq source code when
> blk_mq_tags.active_queues is decremented. Hence add a comment that
> explains this.

That is how it works, applied the patch, thanks Bart.
diff mbox

Patch

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 9aa24c9508f9..266fc4f6b046 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -954,6 +954,12 @@  static void blk_mq_timeout_work(struct work_struct *work)
 		data.next = blk_rq_timeout(round_jiffies_up(data.next));
 		mod_timer(&q->timeout, data.next);
 	} else {
+		/*
+		 * Request timeouts are handled as a forward rolling timer. If
+		 * we end up here it means that no requests are pending and
+		 * also that no request has been pending for a while. Mark
+		 * each hctx as idle.
+		 */
 		queue_for_each_hw_ctx(q, hctx, i) {
 			/* the hctx may be unmapped, so check it here */
 			if (blk_mq_hw_queue_mapped(hctx))