[Kde-pim] Profiling kmail: IdentityManager

[laurent Montel]

Le lundi 16 mai 2016, 09:43:47 CEST David Faure a écrit :
> I used callgrind on kmail and found something interesting.
> 
> Every call to StringUtil::emailAddrAsAnchor (36 calls in my short run)
> creates a KIdentityManagement::IdentityManager instance, which triggers
> Kdelibs4ConfigMigrator in the constructor, which ends up triggering
> reparseConfiguration in the framework integration plugin. That's 36 times
> reparsing the same file for nothing (because surely migration only happens
> once).
> 
> I fixed Kdelibs4ConfigMigrator to only trigger a reparse if needed, and I
> fixed IdentityManager to only do this once, but this again makes me wonder:
> why isn't KIdentityManagement::IdentityManager a singleton?

It was a very old code, Marc created as it.
I never changed it.
Indeed singleton seems to be a good idea.


> I regularly hit performance issues due to the fact that every little bit of
> code which needs identities, has to create an IdentityManager
> first.

Ok I understand the problem.

> Should we make it a singleton, or should we keep trying to make it
> "quick to create", something which seems to regularly fail?
> (see https://git.reviewboard.kde.org/r/126703/ for the last time I hit a
> performance issue in that constructor)
> In Qt, for a class to be "quick to create", it shares an underlying
> singleton for the Private class (see QMimeDatabase, and many others). The
> current approach for IdentityManager (quick until someone adds some slow
> code to the constructor) doesn't seem to work very well.


Ok for me.
(API in kidentitymanager is not stable so you can change it without problem)

-- 
Laurent Montel | laurent.montel at kdab.com | KDE/Qt Senior Software Engineer
KDAB (France) S.A.S., a KDAB Group company
Tel. France +33 (0)4 90 84 08 53,  http://www.kdab.fr


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