From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 18 Aug 2017 08:34:47 -0600 From: Jens Axboe To: Bart Van Assche Cc: linux-block@vger.kernel.org, Christoph Hellwig , Hannes Reinecke , Johannes Thumshirn Subject: Re: [PATCH 03/12] blk-mq: Explain when 'active_queues' is decremented Message-ID: <20170818143446.GA20707@kernel.dk> References: <20170817232311.25948-1-bart.vanassche@wdc.com> <20170817232311.25948-4-bart.vanassche@wdc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20170817232311.25948-4-bart.vanassche@wdc.com> List-ID: On Thu, Aug 17 2017, 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. > > Signed-off-by: Bart Van Assche > Cc: Christoph Hellwig > Cc: Hannes Reinecke > Cc: Johannes Thumshirn > --- > 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