Re: [PATCH 03/12] blk-mq: Explain when 'active_queues' is decremented
flat view
From: Jens Axboe <axboe@kernel.dk>
Date: 2017-08-18 14:34:47
On Thu, Aug 17 2017, Bart Van Assche wrote:
quoted hunk ↗ jump to hunk
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 <redacted> Cc: Christoph Hellwig <hch@lst.de> Cc: Hannes Reinecke <hare@suse.de> Cc: Johannes Thumshirn <redacted> --- block/blk-mq.c | 4 ++++ 1 file changed, 4 insertions(+)diff --git a/block/blk-mq.c b/block/blk-mq.c index f84d145490bf..b86d2cafc355 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c@@ -834,6 +834,10 @@ static void blk_mq_timeout_work(struct work_struct *work) } else { struct blk_mq_hw_ctx *hctx; + /* + * All requests finished (latest request timeout) seconds ago, + * so mark each hctx as idle. + */ queue_for_each_hw_ctx(q, hctx, i) {
I don't think that's a great comment, what does 'latest request timeout' refer to? We hit this case when the device has gone idle, I think a more useful comment would be something about how blk-mq implements timeouts. How about something ala: /* * Request timeouts are handled as a forward rolling timer. If we * end up here, there are no more requests pending, and there hasn't * been for a while. Mark each hctx as idle. */ -- Jens Axboe