linux-kernel - Re: [PATCH] intel_idle: add CPUIDLE_FLAG_IRQ

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Message-ID: <4B2A75D1-84BB-4BA6-B72E-386ED7E483E0@nutanix.com>
Date:   Mon, 13 Nov 2023 15:20:49 +0000
From:   Jon Kohler <jon@...anix.com>
To:     Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>
CC:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Len Brown <lenb@...nel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] intel_idle: add CPUIDLE_FLAG_IRQ_ENABLE to SPR C1 and C1E



> On Nov 12, 2023, at 6:52 AM, Artem Bityutskiy <artem.bityutskiy@...ux.intel.com> wrote:
> 
> On Fri, 2023-11-10 at 20:00 +0000, Jon Kohler wrote:
>> CPUIDLE_FLAG_IRQ_ENABLE
> 
> Hi, yes, I did run several experiments, and found that this change would make
> some micro benchmarks give worse score. I did a lot of repetitions assuming I
> was mixing noise with signal, but every time confirmed that enabling interrupts
> in C1 made the score worse (like 1%).
> 
> I do not have explanation for this phenomena, but decided to not pursue this
> idea.
> 
> Artem. 

Thanks for the follow up. Indeed that is strange on why it would make it worse, but it
is good to know that the shipping configuration is going to work out best.

Thanks,
Jon