[yocto] Bitbake and task offloading onto multiple cloud-based servers

[Flanagan, Elizabeth]

On Fri, Jan 4, 2013 at 2:47 PM, Alex J Lennon
<ajlennon at dynamicdevices.co.uk> wrote:
> On 04/01/2013 22:43, Mark Hatle wrote:
>> On 1/4/13 2:56 PM, Alex J Lennon wrote:
>>>
>>> Can anybody advise on whether bitbake currently supports offloading of
>>> build tasks onto multiple systems? Perhaps cloud based?
>>
>> I see Chris Larson has already answer the main question here.. but I've got some
>> additional insight I can add.
>>
>>> I'm thinking that it would be more efficient for me if I could bring up
>>> a number of Amazon EC2 servers (or similar) then have bitbake
>>> parallelise the build onto those servers to significantly reduce my
>>> build times?
>>
>> In the past I've had people ask me questions about remote builds, parallel
>> building packages, etc.  In the past when I've attempted to figure out if it
>> would be useful, the cost of the data transfer time always comes into play.  How
>> long does it take to simply perform the task locally vs go to the remote
>> machine, perform the task, and get the data back.  For a lot of the tasks that
>> OE does, the remote tasks will end up being slower on a reasonably modern i7 (or
>> similar Xeon) machine.  I'm not sure using something like a cloud server would
>> end up helping due to this.
>>
>
> Thanks for your thoughts Mark.
>
> Another idea that occurred was that it might be interesting if there
> were some metrics available somewhere on recipe build times (are timing
> metrics currently generated in any detail?).

Yes, they're generated by buildstats.bbclass and should be available
within TMPDIR/buildstats. You can also use scripts/pybootchartgui.py
to get a visual representation of the timeline of a build.

-b

>
> Using that as a starting point it might then be possible to determine
> how best to parallelise tasks?
>
>>  From experience I'd say that if anything you'd likely want to modify the
>> bitbake scheduler with some type of locality information.  I.e. if you extract
>> the sources on a node, you most likely want to patch, configure, compile,
>> install, QA and package on that node as well.... but that also means a way to
>> establish node specific tmp/work space is needed for performance as well.
>>
>>> I see bitbake supports a level of task parallelisation on a single box.
>>>
>>> Can parallelisation of build onto multiple systems be achieved?
>>
>> All of the above are possible, but I suspect there is a lot of design and
>> refactoring required to come up with a system that is both efficient and fast.
>>
>>> Is it something that should even be a goal?
>>
>> It's not currently a goal.  But it does get asked about every now and then.  It
>> would be nice to have something more then anecdotal information about if it
>> would be a good idea or not.  This is the type of thing that I think would make
>> an excellent research project.  (Hey and if it makes things able to be built for
>> more people, faster, and cheaper great!  If not, we'd have a more informed
>> response to questions like this.)
>>
>> --Mark
>>
>>> Cheers,
>>>
>>> Alex
>>>
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>>
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-- 
Elizabeth Flanagan
Yocto Project
Build and Release