On 13/10/2021 16:13, John Garry wrote:
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 72a2724a4eee..2a2ad6dfcc33 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -232,8 +232,9 @@ static bool bt_iter(struct sbitmap *bitmap,
unsigned int bitnr, void *data)
if (!rq)
return true;
- if (rq->q == hctx->queue && rq->mq_hctx == hctx)
- ret = iter_data->fn(hctx, rq, iter_data->data, reserved);
+ if (rq->q == hctx->queue && (rq->mq_hctx == hctx ||
+ blk_mq_is_shared_tags(hctx->flags)))
+ ret = iter_data->fn(rq->mq_hctx, rq, iter_data->data, reserved);
blk_mq_put_rq_ref(rq);
return ret;
}
@@ -460,6 +461,9 @@ void blk_mq_queue_tag_busy_iter(struct
request_queue *q, busy_iter_fn *fn,
if (tags->nr_reserved_tags)
bt_for_each(hctx, &tags->breserved_tags, fn, priv, true);
bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false);
+
+ if (blk_mq_is_shared_tags(hctx->flags))
+ break;
}
blk_queue_exit(q);
}
I suppose that is ok, and means that we iter once.
However, I have to ask, where is the big user of
blk_mq_queue_tag_busy_iter() coming from? I saw this from Kashyap's mail:
> 1.31% 1.31% kworker/57:1H-k [kernel.vmlinux]
> native_queued_spin_lock_slowpath
> ret_from_fork
> kthread
> worker_thread
> process_one_work
> blk_mq_timeout_work
> blk_mq_queue_tag_busy_iter
> bt_iter
> blk_mq_find_and_get_req
> _raw_spin_lock_irqsave
> native_queued_spin_lock_slowpath
How or why blk_mq_timeout_work()?
Just some update: I tried hisi_sas with 10x SAS SSDs, megaraid sas with
1x SATA HDD (that's all I have), and null blk with lots of devices, and
I still can't see high usage of blk_mq_queue_tag_busy_iter().
So how about we get this patch processed (to fix
blk_mq_tagset_busy_iter()), as it is independent of
blk_mq_queue_tag_busy_iter()? And then wait for some update or some more
info from Kashyap regarding blk_mq_queue_tag_busy_iter()
Thanks,
John
