View Full Version : rendering threads

04 April 2009, 02:54 AM
is it true that if u have a quad core pc with 4 gigs of ram, and u have your render threads set to 4 it will have to split the 4 gigs of ram for each thread.
so 1 gig of ram for each thread in this case?

that sounds like a problem

04 April 2009, 01:37 AM
Not exactly, I think your getting threads confused with processes. If you set your render threads to 4, then the allocated system memory is split between them, but alot of what is stored in memory like textures, geometry and such are shared between threads. The renderer is getting as much as is available ~4GB minus whats being used (different with 32 or 64bit os), and then the threads use that as they need. each thread will essentially be using all the allocated memory. If you start a seperate render process on each cpu, then each will have to fight over their share of the 4GB. In that case there will be 16 actual threads rendering, 4 for each process. hope that makes sense.

04 April 2009, 02:13 AM
thanks! yea it does.

so in theory , if i have a machine that is getting memory errors, would bringing the threads lower be a way to help that, or no?

04 April 2009, 02:26 AM
I'm not 100% sure about the effect of reducing threads on memory usage, but I don't think its going to make that much of a difference. There are lots more memory optimization tricks that will have way more of an impact. Converting large textures to .map files, optimizing the BSP tree, and geometry optimization are the main ones right off the top of my head.

04 April 2009, 03:59 PM
so if I have an 8 core machine, in the render options do I set threads to 8 or 32?

04 April 2009, 04:52 PM
Set it at 8 threads, That will use 1 thread per core. Render something that takes a minute or so and check your task manager. If the cpu graph reaches 100 percent while rendering then your good to go.

04 April 2009, 07:47 PM
yep. Don't know why I asked, I constantly check my cpu processes all the time when rendering and they are always full.

Oh well. Thanks though.

05 May 2009, 11:14 AM
no. bringing down threads won't enable you overcome memory issues.

05 May 2009, 01:54 PM
yea, i am familiar with most of the memory optimizing techniques. I just heard ,from someone who knows more then me, about the threads thing and i was wondering if it was true, and if so why i hadnt heard it before.

it all makes sense now. thanks all for the info, it was really useful!

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