linux-kernel - RE: [PATCH v3 1/2] cpu/smt: add a notifier to notify the SMT changes

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Date:   Wed, 29 Mar 2023 09:43:09 +0000
From:   "Yang, WenYou" <WenYou.Yang@....com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        "Quan, Evan" <Evan.Quan@....com>,
        "Limonciello, Mario" <Mario.Limonciello@....com>,
        "bp@...en8.de" <bp@...en8.de>,
        "jpoimboe@...nel.org" <jpoimboe@...nel.org>,
        "Phillips, Kim" <kim.phillips@....com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "Yuan, Perry" <Perry.Yuan@....com>,
        "Liang, Richard qi" <Richardqi.Liang@....com>,
        "Li, Ying" <YING.LI@....com>, "Liu, Kun" <Kun.Liu2@....com>,
        "gpiccoli@...lia.com" <gpiccoli@...lia.com>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 1/2] cpu/smt: add a notifier to notify the SMT changes

[AMD Official Use Only - General]



> -----Original Message-----
> From: Peter Zijlstra <peterz@...radead.org>
> Sent: Wednesday, March 29, 2023 4:50 PM
> To: Yang, WenYou <WenYou.Yang@....com>
> Cc: Deucher, Alexander <Alexander.Deucher@....com>; Koenig, Christian
> <Christian.Koenig@....com>; Pan, Xinhui <Xinhui.Pan@....com>; Quan, Evan
> <Evan.Quan@....com>; Limonciello, Mario <Mario.Limonciello@....com>;
> bp@...en8.de; jpoimboe@...nel.org; Phillips, Kim <kim.phillips@....com>;
> tglx@...utronix.de; Yuan, Perry <Perry.Yuan@....com>; Liang, Richard qi
> <Richardqi.Liang@....com>; Li, Ying <YING.LI@....com>; Liu, Kun
> <Kun.Liu2@....com>; gpiccoli@...lia.com; amd-gfx@...ts.freedesktop.org;
> linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v3 1/2] cpu/smt: add a notifier to notify the SMT changes
> 
> Caution: This message originated from an External Source. Use proper caution
> when opening attachments, clicking links, or responding.
> 
> 
> On Wed, Mar 29, 2023 at 07:23:29AM +0000, Yang, WenYou wrote:
> > [AMD Official Use Only - General]
> 
> ^^^ that has no business being in a public email.
> 
> > Hi Peter,
> >
> > Thank you for your review.
> >
> > The purpose of the patch set is to improve the performance when playing
> game for some AMD APUs with SMT enabled/disabled.
> >
> > When change the SMT state on the fly through " echo on/off >
> /sys/devices/system/cpu/smt/control", the kernel needs to send a message to
> notify PMFW to adjust a variable's value, which impacts the performance.
> 
> When top posting I normally ignore the email. When not wrapping email I
> typically get cranky. You 'win' *3* 'I cannot use email' trophies in a singly try.
> Surely AMD has a HOWTO somewhere you can read?

Yes. It is my fault. Sorry.

> 
> So what do you want to have happen when someone goes and manually offlines
> all the SMT siblings using /sys/devices/system/cpu/cpu*/online
> ?

I don't consider this situation.  Any suggestions will be deeply appreciated.

> 
> I'm thinking that wants the same PMFW (whatever the heck that is) notification
> change done, right?
> 
> If the answer is "yes", then your patch does not meet the goals and is
> inadequate.

Yes.  Need to improve.

Thank you.
Wenyou