Re: [dpdk-dev] [PATCH 0/6] power: fix make build for power apps

[David Hunt <david.hunt@intel.com>]

On 13/1/2021 11:18 AM, Burakov, Anatoly wrote:
> On 13-Jan-21 11:14 AM, David Hunt wrote:
>> Hi Anatoly,
>>
>> On 13/1/2021 11:08 AM, Burakov, Anatoly wrote:
>>> On 08-Jan-21 2:30 PM, David Hunt wrote:
>>>> The power example applications that uses the virtio-serial method of
>>>> communication cannot currently be built with make, and can only be 
>>>> built
>>>> using meson/ninja.
>>>>
>>>> The guest channel message definitions and functions in guest_channel.h
>>>> are needed by applications and need to be made public.
>>>>
>>>> This worked pre-20.11, but now with all the meson/ninja changes, 
>>>> making
>>>> these apps externally no longer works. To fix, we need to move the 
>>>> header
>>>> file with the API definitions for the channel commands public, and 
>>>> rename
>>>> the functions accordingly.
>>>>
>>>> The main change is to rename channel_commands.h to
>>>> rte_power_guest_channel.h so that it gets picked up by the 
>>>> installer and
>>>> copied to /usr/local/include. Other changes include renaming 
>>>> #defines to
>>>> have RTE_ at the beginning instead of CPU_. Finally we refactor the 
>>>> code
>>>> to work with those changes.
>>>>
>>>> ---
>>>> v2 changes
>>>>    - re-worked from monolithic patch to a 6 patch patchset for 
>>>> easier review
>>>>
>>>> [PATCH v2 1/6] power: create guest channel public header file
>>>> [PATCH v2 2/6] power: make channel msg functions public
>>>> [PATCH v2 3/6] power: rename public structs
>>>> [PATCH v2 4/6] power: rename defines
>>>> [PATCH v2 5/6] power: add new header file to export list
>>>> [PATCH v2 6/6] power: clean up includes
>>>>
>>>
>>> Just a general question: wouldn't it be better to move this stuff 
>>> entirely into sample app and not bother with keeping it in the 
>>> library? There is precedent - ethtool app has a "library" and an 
>>> "application" part, i think you should be able to move it out of the 
>>> library and into the sample app entirely without too much trouble, 
>>> as code looks to be fairly self-contained.
>>>
>>
>> Agreed, that's a great idea. I could have a common lib under 
>> examples/vm_power_manager, then two apps, vm_power_manager and 
>> guest_cli. That would keep everything nicely local, and not expose 
>> the channel API publicly. The only reason we were making it public 
>> was to allow "make" to work, so that's not a good enought reason, 
>> tbh. I'll throw a prototype together today.
>
> Yep, IIRC Make works perfectly fine with ethtool, so i don't see why 
> it wouldn't work for your sample app as well. Thanks!


Hi Anatoly,

OK, so I was investigating this, and have come across a blocker on this 
method.

There are three methods for managing frequency, acpi, pstate and vm. 
It's the third method that's causing the problem with moving the channel 
functionality out into a sample library alongside vm_power_manger. VM's 
can call channel functions in the power library to affect frequency for 
their cores, and these functions use api function calls and several 
structures and #defines in their code, which is currently part of the 
power management library. These function declarations, structs and 
#defines ere needed in both the examples lib/apps and the power library 
itself, and the prototype changes I made ended up looking very much like 
the patch set that's already on the mailing list.

So, while I would have liked to have a solution along the lines of what 
you've proposed, it's not possible based on the dependencies on common 
structues and #defines.

Thanks for the suggestion, though.

Rgds,
Dave.