[mkgmap-dev] Why does splitter limit the number of threads?

Fri Nov 25 13:05:40 GMT 2011

On Fri, Nov 25, GerdP wrote:

> Hello list,
> 
> the current implementation limits the number of threads to the number of
> available cores.
> I changed the code to allow +2 threads. This results in a much better
> throughput on my dual core machine 
> (e.g. germany.osm.pbf is 100 seconds or 17% faster) with r190 + patchv7.
> What could be the reason for this limit?

Let's say it in this way: In my daily work the experience is, that
most of the time the limitating factor is not the number of cores,
but the I/O bandwith of your harddisk. While in your example with
a dual core machine, the I/O Bandwith should be enough, for some of 
our machines with a 2 digit number of cores, limitating the number
of processes to number of cores/2 or even more makes it much faster.
That's why I think the number of threads should be a config option
which the user can adjust to his hardwre and not a hard number.

  Thorsten

-- 
Thorsten Kukuk, Project Manager/Release Manager SLES
SUSE LINUX Products GmbH, Maxfeldstr. 5, D-90409 Nuernberg
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer, HRB 16746 (AG Nürnberg)