Plugin locator performance ballpark

[Boudewijn Rempt]

On Sun, 8 Sep 2013, David Faure wrote:

> On Thursday 05 September 2013 01:04:52 Sebastian Kügler wrote:
>> Reading just $PLUGINS/kf5, 52 plugins
>>   21893.0 microsec (KServiceTypeTrader)
>>   95835.0 microsec (Metadata)
>> --> Reading metadata is 4-5 slower, ~100ms
>> 
>> Reading $PLUGINS recursively, 127 plugins
>>   20180.0 microsec (KServiceTypeTrader)
>>  347083.0 microsec (Metadata)
>> --> Expectedly, gets worse with more plugins, ~300ms
>
> This is why I think we want an API that is slightly different from 
> KServiceTypeTrader: we want a subdir name into which to narrow the search.
>
> Queries for calligra plugins should only look in $PLUGINS/kf5/calligra/
> Queries for KCModules should only look in $PLUGINS/kf5/kcmodules/
> Queries for kio_thumbnail plugins should only look in 
> $PLUGINS/kf5/thumbcreator/
> etc.
>
> i.e. turning every "service type" into a subdir name. But for more complex 
> cases (e.g. a plugin implementing multiple servicetypes) we can still use 
> additional constraints in the metadata of course.
>
> Querying into a plugins subdir is more Qt-like, too.
>
> However Boud said calligra had 300-400 plugins, so under calligra alone we'd 
> have the same performance as what you just measured for all of $PLUGINS/kf5.
> 300 ms cold cache, 16 ms warm cache. Boud, any opinions? :-)

I like the directoryname idea, and actually, I'd go for a hierarchy:

calligra/filter
calligra/parts
calligra/words
calligra/krita/paintop
calligra/krita/filter
calligra/krita/extensions

etcetera. that should limit the number of plugins per directory to 
something like 30, 40 maximum (for krita/extensions).

>
> The alternative is a cache for all plugins under $PLUGINS/kf5. More ksycoca-
> like in terms of API. But then I'd want the cache to be updated on make 
> install instead (like shared-mime-info). If you're going this road, I have 
> stuff to show you for inspiration (the similar cache for app desktop files, 
> that Ryan Lortie and I designed at the freedesktop summit).
>
>
> PS: staging/ktextwidgets/src/findreplace/kfinddialog.cpp uses 
> KServiceTypeTrader to locate the kregexpeditor plugin, do we agree that it 
> could just look it up by name, e.g. kf5/kregexpeditorgui.so?
> Then ktextwidgets could drop the dependency on KService.
>
> -- 
> David Faure, faure at kde.org, http://www.davidfaure.fr
> Working on KDE, in particular KDE Frameworks 5
>
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