On Tuesday 14 July 2015 19:28:58 Thomas Lübking wrote: > On Dienstag, 14. Juli 2015 19:00:14 CEST, Milian Wolff wrote: > > On Tuesday, July 14, 2015 11:49:25 AM David Faure wrote: > >> On Friday 26 June 2015 18:03:00 Frank Reininghaus wrote: ... > > > > It has. Querying the current time repeatedly is quite costly, > > and often shows > > up in code that extensively uses timers, or > > QDateTime::currentDateTime() etc. > > > > But it's probably still cheaper than querying on-disk meta data > > in the worst > > case, esp. on old rotary disks. > > Actually, checking currentTime() is already the problem here (causing the IO > for the timezone stuff), see > http://marc.info/?l=kde-core-devel&m=143533622526705&w=1 (the 1st paragraph > part of my comment somehow turned into a second-level quote) > > Comparing a monotic timer (QElapsedTime) is however - at least on linux - > close to cost free PLUS: one can have an entirely free "do not check again > during this event cycle" flag.
I used QElapsedTimer in https://codereview.qt-project.org/122247 and the resulting performance improvements are amazing. kbuildsycoca5 is twice faster. -- David Faure, fa...@kde.org, http://www.davidfaure.fr Working on KDE Frameworks 5
