KSyCoca, Thread safety, and Cache invalidation

[Thiago Macieira]

On Tuesday 14 July 2015 19:28:58 Thomas Lübking wrote:
> 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.

If you just need to measure duration, QElapsedTime is your tool. Do not use 
QTime for this, as it can be affected by clock jumps and it accesses the 
timezone.

If you need a machine-comparable time with other systems or across reboots, 
use QDateTime::currentDateTimeUtc(). That avoids refreshing the timezone 
database to convert to local time.

Only use QDateTime::currentDateTime() if you want to show something to the 
user. There's no other valid reason. (writing to a log counts as "showing to 
the user")

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
   Software Architect - Intel Open Source Technology Center
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