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Date:      Thu, 30 Nov 2017 15:47:24 -0500
From:      Jung-uk Kim <jkim@FreeBSD.org>
To:        cem@freebsd.org
Cc:        src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   Re: svn commit: r326383 - head/sys/x86/cpufreq
Message-ID:  <31ee136d-164e-bb9b-3a90-71bb7f55595a@FreeBSD.org>
In-Reply-To: <CAG6CVpUmrf=dLCG8cgtNUZ%2B=V-zwZEzdo88zMh%2BwMP0K=5ka1g@mail.gmail.com>
References:  <201711300140.vAU1e7dC001292@repo.freebsd.org> <CAG6CVpVyooSG3rPG1GvqRZHT9Lyh48JBQb_tFf2-CzWmfW8JyQ@mail.gmail.com> <e412e02d-8b52-221f-1f3c-8c300b1b3067@FreeBSD.org> <CAG6CVpVtm%2BUUw1zxxGXEjKT8MqL8ZjqSaQh4=_0NJbFmcbQxVw@mail.gmail.com> <af56c6b4-d964-4a19-5647-3778eb0cc508@FreeBSD.org> <CAG6CVpUmrf=dLCG8cgtNUZ%2B=V-zwZEzdo88zMh%2BwMP0K=5ka1g@mail.gmail.com>

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From: Jung-uk Kim <jkim@FreeBSD.org>
To: cem@freebsd.org
Cc: src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org,
 svn-src-head@freebsd.org
Message-ID: <31ee136d-164e-bb9b-3a90-71bb7f55595a@FreeBSD.org>
Subject: Re: svn commit: r326383 - head/sys/x86/cpufreq
References: <201711300140.vAU1e7dC001292@repo.freebsd.org>
 <CAG6CVpVyooSG3rPG1GvqRZHT9Lyh48JBQb_tFf2-CzWmfW8JyQ@mail.gmail.com>
 <e412e02d-8b52-221f-1f3c-8c300b1b3067@FreeBSD.org>
 <CAG6CVpVtm+UUw1zxxGXEjKT8MqL8ZjqSaQh4=_0NJbFmcbQxVw@mail.gmail.com>
 <af56c6b4-d964-4a19-5647-3778eb0cc508@FreeBSD.org>
 <CAG6CVpUmrf=dLCG8cgtNUZ+=V-zwZEzdo88zMh+wMP0K=5ka1g@mail.gmail.com>
In-Reply-To: <CAG6CVpUmrf=dLCG8cgtNUZ+=V-zwZEzdo88zMh+wMP0K=5ka1g@mail.gmail.com>

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On 11/30/2017 15:31, Conrad Meyer wrote:
> On Thu, Nov 30, 2017 at 12:08 PM, Jung-uk Kim <jkim@freebsd.org> wrote:=

>> On 11/30/2017 14:32, Conrad Meyer wrote:
>>> Hi,
>>>
>>> I don't think this answers the second question about the conditional.=

>>> It seems like PCPU_GET() for the initial CPU should be pulled out of
>>> the loop, which binds the thread to a different CPU every iteration.
>>
>> Ah, good catch.  I'll fix it soon.  Sorry.
>=20
> Thanks! :-)
>=20
>>> Also, as a side effect of disabling verification, you have fixed PR
>>> 221621, 219213, and probably 218262.
>>
>> Probably.  However, I am just trying to fix my FX-8350 and A10-6800 an=
d
>> I don't have Zen processors to verify the MSRs are actually working on=

>> those CPUs.
>=20
> I have one, I can verify if needed (although the change looks good to
> me).  On some Zen systems (including mine) it seems that the hardware
> can successfully set a P-state, but will fail to read it back.  For me
> it is P1 but other users have reported P0.  That's the root issue of
> all of those PRs.  If reading back isn't required, maybe that's a
> solution to the issue.

Reading back was not really necessary (aka "fire-and-forget").  However,
we wanted to make sure all cores are in the same P-state before
returning to the caller.  Back in the days, it wasn't a big deal because
we only had few cores to deal with and never expected to see complex
topologies such as the Threadripper, I guess. :-/

Jung-uk Kim


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