Re: [PATCH v9 00/12] Support PPTT for ARM64

[Jeremy Linton <jeremy.linton@arm.com>]

Hi,

On 05/29/2018 08:18 AM, Sudeep Holla wrote:
> 
> 
> On 29/05/18 12:56, Geert Uytterhoeven wrote:
>> Hi Sudeep,
>>
>> On Tue, May 29, 2018 at 1:14 PM, Sudeep Holla <sudeep.holla@arm.com> wrote:
>>> On 29/05/18 11:48, Geert Uytterhoeven wrote:
>>>> On Thu, May 17, 2018 at 7:05 PM, Catalin Marinas
>>>> <catalin.marinas@arm.com> wrote:
>>>>> On Fri, May 11, 2018 at 06:57:55PM -0500, Jeremy Linton wrote:
>>>>>> Jeremy Linton (12):
>>>>>>    drivers: base: cacheinfo: move cache_setup_of_node()
>>>>>>    drivers: base: cacheinfo: setup DT cache properties early
>>>>>>    cacheinfo: rename of_node to fw_token
>>>>>>    arm64/acpi: Create arch specific cpu to acpi id helper
>>>>>>    ACPI/PPTT: Add Processor Properties Topology Table parsing
>>>>>>    ACPI: Enable PPTT support on ARM64
>>>>>>    drivers: base cacheinfo: Add support for ACPI based firmware tables
>>>>>>    arm64: Add support for ACPI based firmware tables
>>>>>>    arm64: topology: rename cluster_id
>>>>>>    arm64: topology: enable ACPI/PPTT based CPU topology
>>>>>>    ACPI: Add PPTT to injectable table list
>>>>>>    arm64: topology: divorce MC scheduling domain from core_siblings
>>>>>
>>>>> Queued for 4.18 (without Sudeep's latest property_read_u64 cacheinfo
>>>>> patch - http://lkml.kernel.org/r/20180517154701.GA20281@e107155-lin; I
>>>>> can add it separately).
>>>>
>>>> This is now commit 37c3ec2d810f87ea ("arm64: topology: divorce MC
>>>> scheduling domain from core_siblings") in arm64/for-next/core, causing
>>>> system suspend on big.LITTLE systems to hang after shutting down the first
>>>> CPU:
>>>>
>>>>      $ echo mem > /sys/power/state
>>>>      PM: suspend entry (deep)
>>>>      PM: Syncing filesystems ... done.
>>>>      Freezing user space processes ... (elapsed 0.001 seconds) done.
>>>>      OOM killer disabled.
>>>>      Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
>>>>      Disabling non-boot CPUs ...
>>>>      CPU1: shutdown
>>>>      psci: CPU1 killed.
>>>>
>>>
>>> Is it OK to assume the suspend failed just after shutting down one CPU
>>> or it's failing during resume ? It depends on whether you had console
>>> disabled or not.
>>
>> I have no-console-suspend enabled.
>> It's failing during suspend, the next lines should be:
>>
>>      CPU2: shutdown
>>      psci: CPU2 killed.
>>      ...
>>
> 
> OK, I was hoping to be something during resume as this patch has nothing
> executed during suspend. Do you see any change in topology before and
> after this patch applied. I am interested in the output of:
> 
> $ grep "" /sys/devices/system/cpu/cpu*/topology/*
> 
>>>> For me, it fails on the following big.LITTLE systems:
>>>>
>>>>      R-Car H3 ES2.0 (4xCA57 + 4xCA53)
>>>>      R-Car M3-W (2xCA57 + 4xCA53)
>>>>
>>>
>>> Interesting, is it PSCI based system suspend ?
>>
>> Yes it is.
>>
>> Suspend-to-idle, which doesn't offline CPUs, still works.
>>
> 
>  From DT, I guess this platform doesn't have any idle states.
> Does this use genpd power domains ? I see power-domains in the DT, so
> asking to get more info. Do you have any out of tree patches especially
> if they are depending on some topology cpumasks ?
> 
>>>> System supend still works fine on systems with big cores only:
>>>>
>>>>      R-Car H3 ES1.0 (4xCA57 (4xCA53 disabled in firmware))
>>>>      R-Car M3-N (2xCA57)
>>>>
>>>> Reverting this commit fixes the issue for me.
>>>
>>> I can't find anything that relates to system suspend in these patches
>>> unless they are messing with something during CPU hot plug-in back
>>> during resume.
>>
>> It's only the last patch that introduces the breakage.
>>
> 
> As specified in the commit log, it won't change any behavior for DT
> systems if it's non-NUMA or single node system. So I am still wondering
> what could trigger this regression.
> 

So, presumably the problem is that the numa mask is smaller than the 
normal core_siblings...

I would verify that that there is a behavior change with something like 
/proc/schedstat | cut -d ' ' -f-2

There might be something odd happening with whether you have CONFIG_NUMA 
set (looking at that right now).

So, a couple quick todo's, see if the schedstat domains are changing 
with/without the last patch, and also see if they are changing if you 
enable/disable NUMA.

Why any of that matters for suspend isn't clear at the moment.