[Scons-users] Batching behavior of the Parallel class in Jobs.py

[Andrew C. Morrow]

It does help, thanks for doing the archaeology. Having thought about it in
the context of the links you provided, I agree that the current behavior
makes sense.

On Wed, Oct 5, 2016 at 2:46 PM, Dirk Bächle <tshortik at gmx.de> wrote:

> Hmm,
>
> On 05.10.2016 20:42, Dirk Bächle wrote:
>
>> Hi Andrew,
>>
>> On 05.10.2016 19:57, Andrew C. Morrow wrote:
>>
>>>
>>> I noticed something a little odd, maybe, in the Parallel class:
>>>
>>> https://bitbucket.org/scons/scons/src/ea74a7f7a61561bebfbbfd
>>> 5e7e70c4c346dd8bdb/src/engine/SCons/Job.py?at=default&
>>> fileviewer=file-view-default#Job.py-403:426
>>>
>>> The way I read this, Jobs are processed in 'batches', but this doesn't
>>> seem to be necessary. To experiment with this, I added prints
>>> at lines 396 and 407 to print the number of jobs. The current behavior
>>> when I do a -j12 build looks like:
>>>
>>>
>> thanks for noticing this. I haven't been around back then, but it appears
>> to be an intended change from revision #1281 "Reap as many
>> thread responses as possible at once.  (J.T. Conklin)". It's also
>> reflected in one of the Taskmaster tests, so I'd expect that one
>> to fail with your patch.
>> There's some more info about the background of this change in the threads
>>
>>     http://osdir.com/ml/programming.tools.scons.user/2005-05/
>> msg00025.html
>>     http://osdir.com/ml/programming.tools.scons.user/2005-05/
>> msg00028.html
>>     http://osdir.com/ml/programming.tools.scons.devel/2005-05/
>> msg00011.html
>>
>> but I haven't digested these yet, such that I could say "I understand
>> what they meant". It's definitely *not* an oversight...
>>
>>
> I guess this note by Steven Knight
>
> "This patch should help mitigate any performance bottlenecks SCons may
> have determining the next task when there are outstanding tasks whose
> responses have not yet been processed."
>
> is the key... Does it help?
>
>
> Dirk
>
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