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entryway
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Posts: 2666
Registered: 01-04

VSync = 100% CPU core usage even on MAP01. Why does it happen?

On 2 cores system:
PrBoom-Plus without VSync -> 1500fps -> 50% CPU usage
PrBoom-Plus + VSync -> also 50% CPU usage :(
PrBoom-Plus + VSync + forcing one core with SetProcessAffinityMask -> 5% CPU, lol

GZDoom with VSync -> 50% CPU

Forcing one core 'fixes' high CPU usage. WTF?

Simple test application also works as intended when VSync is enabled - about 5% loading

02-17-13 20:19 #

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Graf Zahl
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Posts: 7451
Registered: 01-03

My guess is it's a driver issue. Maybe it actively waits inside the driver if it runs on multiple cores.

02-17-13 20:59 #

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entryway
Forum Staple

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Graf Zahl said:
My guess is it's a driver issue. Maybe it actively waits inside the driver if it runs on multiple cores.

But it does not affect my simple application. Only 1-2% CPU usage there.

This code also does not help.

code:D_Display()
{
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  SDL_GL_SwapBuffers();
}

Last edited by entryway on 02-17-13 at 21:20

02-17-13 21:05 #

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entryway
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entryway said:
But it does not affect my simple application. Only 1-2% CPU usage there.

By some reasons now it also takes 50%, heh.

02-17-13 21:44 #

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Maes
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Posts: 10166
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AFAIK, unless your application does nothing but passive OS event dispatching/handling, it WILL use all the power of a core unless you include a command explicitly yielding thread control back to the OS.

Now, VSYNC waiting might or might not do just that depending on the implementation at the driver or even at the SDL-driver interaction level.

02-18-13 09:58 #

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printz
CRAZY DUMB ZEALOT

Posts: 8137
Registered: 06-06

Does lack of vertical synchronization get noticed by the human eyes?

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02-18-13 13:09 #

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Mr. T
Senior Member

Posts: 1445
Registered: 12-03

printz said:
Does lack of vertical synchronization get noticed by the human eyes?

Vsync off = https://en.wikipedia.org/wiki/Screen_tearing

02-18-13 13:28 #

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schwerpunk
Senior Member

Posts: 1221
Registered: 05-12

I actually like the horizontal banding effect (from lack of Vsynch) that goes on during a sustained earthquake.

As an aside, the lack of Vsynch is very noticeable in the ZDoom map I'm presently working on for the monochrome project, where I've made a damage sector that flashes between 255 and 32 light level in 1 tic (!). I'd take a screenshot, but well, screenshots don't work that way. :P

02-18-13 13:51 #

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