On 5/9/18 10:57 AM, Mike Galbraith wrote: > On Wed, 2018-05-09 at 09:18 -0600, Jens Axboe wrote: >> On 5/8/18 10:11 PM, Mike Galbraith wrote: >>> 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. >> >> Well, that's good news. Can I get you to try this patch? > > Sure thing. The original hang (minus provocation patch) being > annoyingly non-deterministic, this will (hopefully) take a while. You can verify with the provocation patch as well first, if you wish. Just need to hand-apply since it'll conflict with this patch in bfq. But it's a trivial resolve. -- Jens Axboe
