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 07:23:29 +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@...e.de" <bp@...e.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]

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.

Best Regards,
Wenyou

> -----Original Message-----
> From: Peter Zijlstra <peterz@...radead.org>
> Sent: Wednesday, March 29, 2023 3:10 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@...e.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 09:51:48AM +0800, Wenyou Yang wrote:
> > Add the notifier chain to notify the cpu SMT status changes
> >
> 
> Why!?!? What's the purpose of all this? IIRC this doesn't trigger if you manually
> disable all the siblings. And because you didn't tell us why you need this I can't
> tell you if that matters or not :/