Lag after resume culprit found

[Andriy Gapon]

On 17/05/2018 10:56, Johannes Lundberg wrote:
> 
> 
> On Thu, May 17, 2018 at 8:46 AM, Johannes Lundberg <johalun0 at gmail.com
> <mailto:johalun0 at gmail.com>> wrote:
> 
> 
> 
>     On Thu, May 17, 2018 at 7:43 AM, Andriy Gapon <avg at freebsd.org
>     <mailto:avg at freebsd.org>> wrote:
> 
>         On 17/05/2018 02:07, Johannes Lundberg wrote:
>         > https://github.com/freebsd/freebsd/commit/66f063557f257baa9c8aeab9f933171eaa6e1cfa
>         <https://github.com/freebsd/freebsd/commit/66f063557f257baa9c8aeab9f933171eaa6e1cfa>
>         > x86 cpususpend_handler: call wbinvd after setting suspend state bits
> 
>         That's very interesting and surprising.
>         That commit changes something that happens before suspend, it should not
>         have
>         any effect on the system state after resume.
> 
>         Does anyone have a theory of what could be wrong?
> 
> 
>     Nope but moving
>             CPU_CLR_ATOMIC(cpu, &suspended_cpus);
>     back to the end of that scope fixes it.
>      
> 
> 
> I did some further testing.
> Calling
> CPU_CLR_ATOMIC(cpu, &suspended_cpus);
> before
> pmap_init_pat();
>  is what "breaks" resume.
> 
> Is this Intel only or this it happen on AMD as well (which this patch was
> intended for)?

Not sure about the PAT part, but fpuresume/npxresume would affect all platforms.
It's a bit puzzling that doing PAT manipulations on one AP while another AP is
being brought up is problematic.  Probably there is something that I am missing.

Thank you very much again for zeroing in on it.

>         > 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.


-- 
Andriy Gapon