[Scons-users] Hi, wondering about possible speed ups to scons

[Bill Deegan]

But maybe running your editor via strace and watching file write events or
just /proc/editor_pid/fd's might yield something interesting.

Monitoring all files for change is really a huge shotgun approach to a
(perceived) problem better solved with simpler, lighter weight tools.

That said, running SCons in interactive mode should help quite a bit if
you're worried about rebuilds.
Also there's a new slots branch which has some speedup/memory reduction
code which might be worth a try.

-Bill

On Thu, Mar 5, 2015 at 10:48 AM, Bill Deegan <bill at baddogconsulting.com>
wrote:

> To add to what Dirk said, you also need to test such on a non-local
> filesystem (NFS...)
>
> -Bil
>
> On Thu, Mar 5, 2015 at 3:27 AM, Dirk Bächle <tshortik at gmx.de> wrote:
>
>> Hi Ben,
>>
>> On 05.03.2015 00:52, Schleimer, Ben via Scons-users wrote:
>>
>>> Hi Y'all,
>>>     First of all, I'd like to say that I use SCons all of the time for
>>> my C++ projects and it's by far the best build system I've
>>> had the pleasure to work with. I especially like the ease of using the
>>> Qt4 tools and precompiled header support, yada yada yada...
>>>
>>>
>> that's really nice to hear. Thanks a lot for the positive feedback!
>>
>>  Secondly, I've been thinking about all of the criticism aimed at scons
>>> for not being fast enough.
>>> I understand that python is inheritantly slow (ignoring cython, etc..)
>>> but it seems like SCons could easily design it's way out of
>>> this problem.
>>>
>>>
>> Did you have a look at http://www.scons.org/wiki/WhySconsIsNotSlow yet?
>> Especially the numbers at the bottom of the page will be what you have to
>> beat with your solution. There also exists a pre-edit version of the talk I
>> gave at the PyconFr 2014 in Lyon (http://www.pycon.fr/2014/
>> schedule/presentation/25/), the download URL is:
>>
>>   http://dl.afpy.org/pycon-fr-14/videos/25-10-2014-112947_bd16.mp4
>>
>>
>>  I'm wondering if the design change for SCons I'm about to propose has
>>> been proposed before:
>>>
>>>
>> Yes, it has...lots of times. ;) These kind of approaches always seem to
>> work well, assuming that SCons has a DAG that is statically created in the
>> background, and then simply traversed during the build step. But that's not
>> true, SCons detects the dependencies on-the-fly while building targets.
>> There is no explicit structure that you can point to and refer to as "the
>> DAG". It's somehow implicitly given since each Node stores its children,
>> and this is the info that gets updated continuously during the single build
>> steps.
>> So, having a data structure as "the DAG" and update its nodes, will not
>> directly map to what SCons uses internally to figure out which targets are
>> up-to-date or need to get rebuilt.
>>
>>  1) Create a scons daemon (sconsd) that stays resident and watches a
>>> particular SConstruct file and all of its generated
>>> dependencies. Whenever any of the dependencies change or is deleted,
>>> scons updates the dependency graph in the background.
>>>
>>> 2) When the user actually runs scons to compile, the dependency graph is
>>> ready to be immediately traversed and all of the Nodes built.
>>>
>>> Thoughts? Ideas?
>>>
>>>
>> What about the Nodes that get generated during the build itself? What if
>> I want to compile/build only a part of the complete DAG (a single
>> subdirectory) and then later on possibly build the whole thing? How to
>> ensure that things like build infos for the single Nodes/Targets get
>> properly merged/updated between those two separate runs?
>>
>> And how will such a daemon behave performance-wise on a project with
>> 50000+ C files? My guess is that there would be a lot of stat()ing going
>> on...and wrapped in a package like watchdog, one would have to make a
>> simple testcase first and try to profile some decent numbers out of it.
>> Then watch the scaling behaviour...and if that looks okay, we can talk
>> about how to integrate such a thing into SCons. ;)
>>
>> Just a few first thoughts...
>>
>> Best regards,
>>
>> Dirk
>>
>>
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>
>
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