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Date:      Thu, 17 May 2018 11:06:42 +0300
From:      Andriy Gapon <avg@FreeBSD.org>
To:        Johannes Lundberg <johalun0@gmail.com>
Cc:        freebsd-current <freebsd-current@freebsd.org>
Subject:   Re: Lag after resume culprit found
Message-ID:  <4d69b9f6-9406-74ba-1780-ac783adcf107@FreeBSD.org>
In-Reply-To: <CAECmPwuKoQaD0M-wJagns_YCDMLy_qMnuy%2BceLF5UZtfE_1ehg@mail.gmail.com>
References:  <CAECmPwtULDe9GGK0PhnUa7_n=zxripJj9nh5m0RTF9XqKhXKYQ@mail.gmail.com> <acaa419d-891e-96b1-7c1f-3203857c07ec@FreeBSD.org> <CAECmPwsgQhMM6zu=EfV=DQ4VHzEMuQUjD%2B45O-TP=A2U9mM8Qg@mail.gmail.com> <CAECmPwuKoQaD0M-wJagns_YCDMLy_qMnuy%2BceLF5UZtfE_1ehg@mail.gmail.com>

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On 17/05/2018 10:56, Johannes Lundberg wrote:
> 
> 
> On Thu, May 17, 2018 at 8:46 AM, Johannes Lundberg <johalun0@gmail.com
> <mailto:johalun0@gmail.com>> wrote:
> 
> 
> 
>     On Thu, May 17, 2018 at 7:43 AM, Andriy Gapon <avg@freebsd.org
>     <mailto:avg@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



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