On Wed, 15 Jun 2016, Arjan van de Ven wrote:
> what would 1 more timer wheel do?
Waste storage space and make the collection of expired timers more expensive.
The selection of the timer wheel properties is combination of:
1) Granularity
2) Storage space
3) Number of levels to collect
#1 Influences the accuracy of the wheel levels. The worst case error is the
ratio of the shortest timeout in a level and the granularity of that level.
Currently I've chosen 12.5%. If we go to 25% worst case, then we increase
the per level capacity by factor (1 << lvl).
#2 It strikes me a bit silly to waste storage space for esoteric
outliers. According to the data I collected we have no timers at all
between 2hrs and 5 days.
#3 The more levels we have the more steps we have when collecting expired
timers or searching the next expiring timer. It's all bound, but it still
adds up.
Thanks,
tglx
