Messages in this thread | | | Subject | Re: bug in tag handling in blk-mq? | From | Mike Galbraith <> | Date | Wed, 09 May 2018 06:11:29 +0200 |
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On Tue, 2018-05-08 at 19:09 -0600, Jens Axboe wrote: > > Alright, I managed to reproduce it. What I think is happening is that > BFQ is limiting the inflight case to something less than the wake > batch for sbitmap, which can lead to stalls. I don't have time to test > this tonight, but perhaps you can give it a go when you are back at it. > If not, I'll try tomorrow morning. > > If this is the issue, I can turn it into a real patch. This is just to > confirm that the issue goes away with the below.
Confirmed. Impressive high speed bug stomping.
> diff --git a/lib/sbitmap.c b/lib/sbitmap.c > index e6a9c06ec70c..94ced15b6428 100644 > --- a/lib/sbitmap.c > +++ b/lib/sbitmap.c > @@ -272,6 +272,7 @@ EXPORT_SYMBOL_GPL(sbitmap_bitmap_show); > > static unsigned int sbq_calc_wake_batch(unsigned int depth) > { > +#if 0 > unsigned int wake_batch; > > /* > @@ -284,6 +285,9 @@ static unsigned int sbq_calc_wake_batch(unsigned int depth) > wake_batch = max(1U, depth / SBQ_WAIT_QUEUES); > > return wake_batch; > +#else > + return 1; > +#endif > } > > int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth, >
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