Plugin locator performance ballpark

[Sebastian Kügler]

On Sunday, September 08, 2013 11:17:56 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?
> 
> 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).

Martin Grässlin asked if we could offer an async API for this. Opinions?

> 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.

I don't have problems with that, but I'm also hardly affected by it. :)
-- 
sebas

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