linux-kernel - Re: [PATCH v1] platform/x86: intel_pmc_core: promote S0ix failure warn() to WARN()

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Date:   Mon, 31 Oct 2022 21:15:44 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     "Limonciello, Mario" <Mario.Limonciello@....com>,
        Sven van Ashbrook <svenva@...omium.org>,
        Rajneesh Bhardwaj <irenic.rajneesh@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "S-k, Shyam-sundar" <Shyam-sundar.S-k@....com>,
        "rrangel@...omium.org" <rrangel@...omium.org>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>,
        Rajneesh Bhardwaj <rajneesh.bhardwaj@...el.com>,
        Rafael J Wysocki <rjw@...ysocki.net>,
        Rajat Jain <rajatja@...gle.com>,
        David E Box <david.e.box@...el.com>,
        Mark Gross <markgross@...nel.org>
Subject: Re: [PATCH v1] platform/x86: intel_pmc_core: promote S0ix failure
 warn() to WARN()

Hi,

On 10/31/22 20:39, Limonciello, Mario wrote:
> [Public]
> 
>> -----Original Message-----
>> From: Sven van Ashbrook <svenva@...omium.org>
>> Sent: Friday, October 28, 2022 23:12
>> To: Rajneesh Bhardwaj <irenic.rajneesh@...il.com>; Hans de Goede
>> <hdegoede@...hat.com>
>> Cc: Limonciello, Mario <Mario.Limonciello@....com>; LKML <linux-
>> kernel@...r.kernel.org>; S-k, Shyam-sundar <Shyam-sundar.S-
>> k@....com>; rrangel@...omium.org; platform-driver-
>> x86@...r.kernel.org; Rajneesh Bhardwaj <rajneesh.bhardwaj@...el.com>;
>> Rafael J Wysocki <rjw@...ysocki.net>; Rajat Jain <rajatja@...gle.com>;
>> David E Box <david.e.box@...el.com>; Mark Gross <markgross@...nel.org>
>> Subject: Re: [PATCH v1] platform/x86: intel_pmc_core: promote S0ix failure
>> warn() to WARN()
>>
>> On Thu, Oct 27, 2022 at 12:02 PM Rajneesh Bhardwaj
>> <irenic.rajneesh@...il.com> wrote:
>>> I'd advise against this promotion based on my experience with S0ix entry
>> failures.
>>
>> On Thu, Oct 27, 2022 at 11:40 AM Hans de Goede <hdegoede@...hat.com>
>> wrote:
>>> I'm not a fan of the change you are suggesting here.
>>
>> Thanks everyone for the feedback. Looks like there is consensus that it's
>> not advisable to promote the warning. We will move forward with changes to
>> our monitoring infrastructure instead.
> 
> Did you see the idea proposed by David Box to introduce some infrastructure in
> the kernel for this?
> 
> Just thinking about it a little bit more, it could be a lot nicer to have something like:
> 
> /sys/power/suspend_stats/last_hw_deepest_state
> 
> During the resume process drivers such as amd_pmc and intel_pmc_core could
> read the appropriate values for the hardware and call a function that would
> populate it with either a "0" or "1" or maybe even the amount of time spent in
> that state.
> 
> We could then retire the debugging messages from both drivers and instead of
> your infrastructure relying upon scanning logs, userspace could read that sysfs
> file after every suspend and raise the alarms when it's 0 (or if it's populated with
> time smaller than X% of the total suspend time).

Something like this does indeed sound like a nice solution for this.

Regards,

Hans