POV-Ray : Newsgroups : povray.general : Threads and rendering performance : Re: Threads and rendering performance Server Time
3 Mar 2024 12:59:15 EST (-0500)
  Re: Threads and rendering performance  
From: William F Pokorny
Date: 1 Dec 2023 08:57:34
Message: <6569e64e$1@news.povray.org>
On 11/30/23 09:23, Chris R wrote:
> So, I looked into limiting the number of worker threads in POV-Ray to make sure
> there was always some spare capacity to do other things without triggering
> whatever Windows 11 bug is causing this.  My machine has 14 cores and 20 logical
> processors.  Running with the default settings, it would peg all 20 logical
> processors at or near 100% when doing a large render.  Doing some experiments I
> verified that worker threads take up one logical processor (vs cores).  I ended
> up settling on a new default using 12 worker threads instead of the max, which
> based on performance monitoring tools runs at about 50% overall CPU utilization.
> 
> The odd thing I've noticed, though, is that my renders are not significantly
> slower.

I think Jerome, now a long time ago, did some detailed analysis on the 
value of threads overs cores. I cannot immediately find it... I believe 
it showed there is some, but not great value to POV-Ray where threads 
exceed the number of physical cores. I think he showed Something like a 
gain of another 10-15% in performance.

This aligns more roughly with my own experience too. Physical cores 
matter most, but it is usually still a gain to use most or all of the 
available threads (apparent / logical cores).

Bill P.


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