linux-kernel - Re: S3 resume regression [1cf4f629d9d2 ("cpu/hotplug: Move online calls to hotplugged cpu")]

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Date:   Thu, 27 Oct 2016 23:37:45 +0300
From:   Ville Syrjälä <ville.syrjala@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Feng Tang <feng.79.tang@...il.com>, feng.tang@...el.com,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-arch@...r.kernel.org, Rik van Riel <riel@...hat.com>,
        "Srivatsa S. Bhat" <srivatsa@....edu>,
        Peter Zijlstra <peterz@...radead.org>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Rusty Russell <rusty@...tcorp.com.au>,
        Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Paul Turner <pjt@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Zhang, Rui" <rui.zhang@...el.com>,
        Len Brown <len.brown@...el.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>
Subject: Re: S3 resume regression [1cf4f629d9d2 ("cpu/hotplug: Move online
 calls to hotplugged cpu")]

On Thu, Oct 27, 2016 at 09:25:05PM +0200, Thomas Gleixner wrote:
> On Thu, 27 Oct 2016, Ville Syrjälä wrote:
> > On Thu, Oct 27, 2016 at 08:48:57PM +0200, Thomas Gleixner wrote:
> > > What that old patch did, was:
> > > 
> > > 1) Make sure that the broadcast device is actually armed at resume.
> > > 
> > >    That might cause the HPET to resume proper.
> > > 
> > > 2) Force a max. 3 seconds rearm when the targeted expiry time is > than 10
> > >    seconds
> > > 
> > >    That might make sure that lower C-States are never entered.
> > 
> > Doh. I lost the other hunk somewhere. Let's try that again... And indeed
> > with the other hunk in tow the machine would appear to resume properly.
> 
> So it would be interesting whether that hunk in resume_broadcast() is
> sufficient.

So far it looks like the answer is yes.

Looks to be about 5 seconds slower than acpi-idle in resuming, but
I suppose that's not all that surprising ;)

>  
> > > What's the lowest C-State with acpi-idle and what's the lowest one with
> > > intel_idle?
> > 
> > acpi_idle
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/desc:ACPI FFH INTEL MWAIT 0x30
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/disable:0
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/latency:100
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/name:C3
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/power:0
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/residency:200
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/time:5677316
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/usage:5920
> > 
> > intel_idle:
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/desc:MWAIT 0x30
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/disable:0
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/latency:100
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/name:C4-ATM
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/power:0
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/residency:400
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/time:7146705
> > /sys/devices/system/cpu/cpu0/cpuidle/state3/usage:6826
> 
> Does the machine work, when you limit intel idle to C3, which would then
> match acpi idle ?

I'm pretty sure I had tested all of these, but I just double checked
to make sure. There's no C3 with intel_idle so I limited to C2, but
that did not help.

Isn't it possible that ACPI C3 is in fact C4? I thought ACPI C-states
are always numbered non-sparsely, and in this case ACPI C3 could be
anything from C3 to C11 (if the processor actually supported such
states obviously). Actually now that I look at the descriptions for
the states in sysfs, it says "MWAIT 0x30" for state3 on both drivers,
which I presume means it's in fact C4 for both.

-- 
Ville Syrjälä
Intel OTC