Lag after resume culprit found

[Johannes Lundberg]

https://github.com/freebsd/freebsd/commit/66f063557f257baa9c8aeab9f933171eaa6e1cfa
x86 cpususpend_handler: call wbinvd after setting suspend state bits

How to test (i915kms)

Start X with glxgears
Confirm running stable at 60 fps
suspend/resume (S3)
glxgears is now fluctuating between 10-40 fps.


Way past bedtime now so I stop here for today.

Note: cross-posting - please think before "reply-to-all"

/Johannes