[Bf-committers] [Bf-blender-cvs] SVN commit: /data/svn/bf-blender [13774] trunk/blender/source: automatic threads, next to the Threads button, so you can set threads to use whatever the system has, useful in the studio with 2, 4, 8 core systems w

[Campbell Barton]

On Fri, Feb 22, 2008 at 11:37 PM, Joe Eagar <joeedh at gmail.com> wrote:
> Campbell Barton wrote:
>  > Revision: 13774
>  >           http://projects.blender.org/plugins/scmsvn/viewcvs.php?view=rev&root=bf-blender&revision=13774
>  > Author:   campbellbarton
>  > Date:     2008-02-19 23:23:21 +0100 (Tue, 19 Feb 2008)
>  >
>  > Log Message:
>  > -----------
>  > automatic threads, next to the Threads button, so you can set threads to use whatever the system has, useful in the studio with 2,4,8 core systems when sharing files.
>  >
>  >
>  BTW, standard is usually to use number of cores + 1, as this takes
>  advantage of the way schedulers work and also things like hyperthreading.
>
>  Actually, in my own tests (and other's) having lots and lots of threads
>  (like 4-5 for my single core systems) seems to be a lot faster then the
>  normal number of CPUs + 1.  However, there's been no rigorous testing of
>  this phenomenon that I know of, so I'd recommend following the CPUs+1 rule.
>
>  Joe

Hi, Your probably right that threads+1 makes full use of the CPU(s),
however I still think setting the threads to the number of processors
is a good default for new users.
Its also possible that some CPU's do worse at multi threading on a
single core (tho probably not new CPU's Id hope) as well as the
overhead of an extra thread (uses some more memory, which could be a
fair bit more with some blend files)

My rationale for auto-threads: Its significantly better for new users
with dual core systems (who might not think to change the threads),
but experienced users can tweak this for their own scene's taking
memory usage and the overhead of an extra thread into account.

So for now I think this is ok. if people feel strongly about this - It
would be good to show some examples of how much better threads+1 is.