blk-mq: add trace block plug and unplug for multiple queues

Yufen Yu · axboe · commit ff3b74b8e167 · 2019-04-02T08:57:05.000-06:00
For now, we just trace plug for single queue device or drivers
provide .commit_rqs, and have not trace plug for multiple queues
device. But, unplug events will be recorded when call
blk_mq_flush_plug_list(). Then, trace events will be asymmetrical,
just have unplug and without plug.

This patch add trace plug and unplug for multiple queues device in
blk_mq_make_request(). After that, we can accurately trace plug and
unplug for multiple queues.

Reviewed-by: Christoph Hellwig &lt;hch@lst.de&gt;
Signed-off-by: Yufen Yu &lt;yuyufen@huawei.com&gt;
Signed-off-by: Jens Axboe &lt;axboe@kernel.dk&gt;
diff --git a/block/blk-mq.c b/block/blk-mq.c
@@ -2003,11 +2003,13 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 			plug->rq_count--;
 		}
 		blk_add_rq_to_plug(plug, rq);
+		trace_block_plug(q);
 
 		blk_mq_put_ctx(data.ctx);
 
 		if (same_queue_rq) {
 			data.hctx = same_queue_rq->mq_hctx;
+			trace_block_unplug(q, 1, true);
 			blk_mq_try_issue_directly(data.hctx, same_queue_rq,
 					&cookie, false, true);
 		}

Original file line number	Diff line number	Diff line change
`@@ -2003,11 +2003,13 @@ static blk_qc_t blk_mq_make_request(struct request_queue q, struct bio bio)`
`2003`	`2003`	`plug->rq_count--;`
`2004`	`2004`	`}`
`2005`	`2005`	`blk_add_rq_to_plug(plug, rq);`
	`2006`	`+ trace_block_plug(q);`
`2006`	`2007`
`2007`	`2008`	`blk_mq_put_ctx(data.ctx);`
`2008`	`2009`
`2009`	`2010`	`if (same_queue_rq) {`
`2010`	`2011`	`data.hctx = same_queue_rq->mq_hctx;`
	`2012`	`+ trace_block_unplug(q, 1, true);`
`2011`	`2013`	`blk_mq_try_issue_directly(data.hctx, same_queue_rq,`
`2012`	`2014`	`&cookie, false, true);`
`2013`	`2015`	`}`