random system freezes when writing to NVMe drive

[X512]

This is hrev58057.

Steps to reproduce:

1. Run dd command.

   > dd if=/dev/zero of=zero bs=16M count=4096
   4096+0 records in
   4096+0 records out
   68719476736 bytes (69 GB, 64 GiB) copied, 57.0299 s, 1.2 GB/s
   

2. Contentiously move mouse pointer while dd command is running. Pointer will stop and freeze sometimes. Issue can be also observed in lagging animations, for example Pe editor about window animation.

[waddlesplash]

Doesn't seem to happen here (NVMe in VMware, with a real NVMe for the underlying disk).