Re: blk-mq request allocation stalls

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On 01/12/2015 09:12 AM, Bart Van Assche wrote:
On 01/12/15 16:42, Jens Axboe wrote:
On 01/12/2015 07:46 AM, Bart Van Assche wrote:
bt_get: __bt_get() returned -1
queue_num=2, nr_tags=62, reserved_tags=0, bits_per_word=3
nr_free=62, nr_reserved=0, may_queue=0
active_queues=8

Can you add dumping of hctx->nr_active when this fails? You case is that
the may_queue logic says no-can-do, so it smells like the nr_active
accounting is wonky since you have supposedly no allocated tags, yet it
clearly thinks that you do.

Hello Jens,

The requested output is as follows:

bt_get: __bt_get() returned -1
queue_num=0, nr_tags=62, reserved_tags=0, bits_per_word=3
nr_free=62, nr_reserved=0, hctx->tags->active_queues=7,
hctx->nr_active=9, hctx_may_queue()=0
active_queues=7

So that does look a bit off, we have (supposedly) 9 active requests, but nothing allocated. When the mkfs is done and things are idle, can you try and cat the 'active' file in the mq directory? I want to see if it drops to zero or stays elevated.

--
Jens Axboe

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