[nvmewin] finally root caused - strange DPC watchdog issue

[Luse, Paul E]

So its not Chatham and its not some complex mapping issue or crazy corner case... we were failing to set StorPortSetDeviceQueueDepth() per lun.  I knew about this but incorrectly recalled that the default was 254, its actually 20.  When I set it to 254 the odd imbalance in CPU load (and the watchdog issues) goes away.  Apparently having an optimal miniport and a heavy IO load with a low storport queue depth exposes this problem in storport as when I mix up the submit/msix cores and leave the queue depth at 20 it goes away.

I'll prepare my patch accordingly and send it out tomorrow....

Thx
Paul

____________________________________
Paul Luse
Sr. Staff Engineer
PCG Server Software Engineering
Desk: 480.554.3688, Mobile: 480.334.4630

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