linux-kernel - Re: [RFC PATCH 00/10] arch/x86: AMD QoS support

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Message-ID: <5fc7797c-6246-d865-9232-cbe26b833fec@amd.com>
Date:   Fri, 5 Oct 2018 17:03:51 +0000
From:   "Moger, Babu" <Babu.Moger@....com>
To:     James Morse <james.morse@....com>
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Subject: Re: [RFC PATCH 00/10] arch/x86: AMD QoS support

Hi James,

On 10/05/2018 11:18 AM, James Morse wrote:
> Hi Babu,
> 
> (Thanks for looping me in!)
> 
> On 28/09/18 02:57, Moger, Babu wrote:
>>> On Mon, 24 Sep 2018, Moger, Babu wrote:
>>>
>>>> This series adds support for AMD64 architectural extensions for Platform
>>>> Quality of Service. These extensions are intended to provide for the
>>>> monitoring of the usage of certain system resources by one or more
>>>> processors and for the separate allocation and enforcement of limits on
>>>> the use of certain system resources by one or more processors.
>>>>
>>>> The monitoring and enforcement are not necessarily applied across the
>>>> entire system, but in general apply to a QOS domain which corresponds to
>>>> some shared system resource.  The set of resources which are monitored
>>> and
>>>> the set for which the enforcement of limits is provided are implementation
>>>> dependent. Platform QOS features are implemented on a logical processor
>>> basis.
>>>> Therefore, multiple hardware threads of a single physical CPU core may
>>> have
>>>> independent resource monitoring and enforcement configurations.
>>>>
>>>> AMD's next generation of processors support following QoS sub-features.
>>>> - L3 Cache allocation enforcement
>>>> - L3 Cache occupancy monitoring
>>>> - L3 Code-Data Prioritization support
>>>> - Memory Bandwidth Enforcement(Allocation)
>>>>
>>>> The public specification is still in works. Will add the link when it is
>>>> available.
>>>>
>>>> Obviously, there are multiple ways we can go about these changes. We felt
>>>> it is appropriate to rename and re-organize the code little bit before
>>>> making the functional changes. The first few patches(1-6) renames and
>>>> re-organizes the sources in preparation. Rest of the patches(7-10) adds
>>>> support for AMD QoS features.
>>>
>>> On the first glance this all looks sensible, but there is work in progress
>>> by James Morse (Cc'ed), who wants to generalize the resctrl filesystem so
>>> it can be reused by ARM. I just want to make sure that your reorganization
>>> is not colliding or creating duplicate effort.
> 
> Aha, some of this makes my life easier. I'm against having the ABI different
> between architectures. This meant contiguous bitmaps on arm, which the MPAM
> stuff doesn't actually require...
> 
> 
>> Thanks for pointing this out. I have looked thru James patches. It appears this
>> series is only a small part of his much bigger change. Don't know the timeframe
>> of his overall changes.
>> I will let him speak on that.
> 
> Longer, as its more invasive,

Ok. Thanks for the heads up.

> 
> 
>> That being said, I don't consider our efforts as
>> duplicate. He is touching the resource structures, and trying to separate arch,
>> non-arch components.
>> My changes are mostly inside the resource structures(mostly resource handlers)
> 
>> and trying to accommodate minor differences within the architecture.  It will
>> be mostly involve rebase
>> effort on either side in the end whoever goes first.
> 
>> James, What are your thoughts? 
> 
> I think your stuff should go first. It doesn't look like you are adding new
> features/controls, so its normally:painful for me to rebase over it.
> (doing it the other-way round would be harder!)

Ok. Sounds good. I will send v2 version soon. Feel free to review.


> 
> 
> Thanks,
> 
> James
>