[Bf-committers] BLENDER_MAX_THREADS limits & SCONS

[Roger Wickes]

wiki updated http://wiki.blender.org/index.php/Manual/Rendering_Options#Options

I think there is a hard-coded limit of 64 tiles vertical (YParts cannot be >64).

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________________________________
From: Ton Roosendaal <ton at blender.org>
To: bf-blender developers <bf-committers at blender.org>
Sent: Thursday, October 23, 2008 5:32:52 AM
Subject: Re: [Bf-committers] BLENDER_MAX_THREADS limits & SCONS

Hi,

There used to be some hardcoded limits still keeping it on max 8 (using 
bitflags), but afaik Brecht has cleaned that up.

What still will limit the amount of threads is the fact that per thread 
memory is allocated too, each thread does a full tile render. Further 
almost all geometry (render faces/vertices) is checked for each tile it 
renders, giving some extra overhead.
There's also thread tables for AO and area-shadow lamp sampling, 
precalculated and allocated in advance.
Lastly; there's still quite some locking going on, for each malloc for 
example.

A quick rule-of-thumb is to make sure the total number of threads 
renders less than one quarter of the entire image, to prevent too much 
memory allocated:

8 threads: use 64 tiles
16 threads: use 128 tiles
128 threads: use 1024 tiles

Whether such giant amount of tiles gives inacceptable overhead is 
unknown, but quite likely. If you use heavy raytracing on relatively 
simple scenes it might work though.

BTW: are we getting 64 bits irix versions? Would be nice :)

-Ton-

------------------------------------------------------------------------
Ton Roosendaal  Blender Foundation  ton at blender.org    www.blender.org
Blender Institute BV  Entrepotdok 57A  1018AD Amsterdam The Netherlands

On 22 Oct, 2008, at 22:45, Timothy Baldridge wrote:

> A few questions. I've build Blender on IRIX via MIPSPro and we're in
> the process of testing it. One of my testers complained about the 8
> thread limit, as some IRIX machines the testers have access to can be
> up in the 32-64 CPU range. I remember there being some issues in the
> past with changing this number to be too high. Are there any internal
> limits to changing this to a higher number such as 128?
>
> Also, I wonder if anyone would complain if I made BLENDER_MAX_THREADS
> changable via Scons? something like
>
> #ifndef BLENDER_MAX_THREADS
> #define BLENDER_MAX_THREADS 8
> #endif
>
> That way we could compile for the number of cores based on the 
> platform.
>
> Timothy
>
> -- 
> Two wrights don't make a rong, they make an airplane. Or bicycles.
> _______________________________________________
> Bf-committers mailing list
> Bf-committers at blender.org
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