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Render Bottle-necking!

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Mike BlutsteinRender Bottle-necking!
by on Feb 12, 2014 at 6:03:32 am

Hi guys!

I just upgraded my system from 16gb RAM, Radeon 5770 -> 32 GB RAM GTX 780.

My processor is an i7 2600k.

My question is, how come my renders are not significantly speeding up on some projects? On a basic 3D one, my render shot from 45 minutes to 50 seconds (wow, i know). And I am NOT complaining about that!

However, on this other project with more plugins and less 3D stuff, my render took about the same amount of time. I would normally attribute this to something being bottle-necked, however I cannot see what would be doing it! My CPU usage is at like 20% constantly, my RAM is at like 15% constantly, and my GPU is definitely not bottle-necking it here. What is stopping my render from taking a few minutes as apposed to 1 hour for a 3 minute clip with some keying and such.

Any tips you can give me would help! I currently have my settings on Render multiple frames at once, with 1.5 GB ram given to the other cores and 1 available for background. Also, i dedicated 6 gb of RAM to the background processes. Thank you for the tips!

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Mike BlutsteinRe: Render Bottle-necking!
by on Feb 12, 2014 at 6:10:40 am

Oh also, I am using a Crucial M4 SSD for my cache/files and rendering.

I also made sure to purge my memory and everything before rendering down!

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Shane SmiskolRe: Render Bottle-necking!
by on Feb 12, 2014 at 9:35:55 am

I am just a beginner at this type of stuff, but, how many cores does your CPU have (goto task manager)? If multiple, are all of them being used when rendering? Some effects are multi-core effects and some are not, it depends on what you use, but for me, to use all of them and achieve faster rendering, open After Effcts and go to Preferences, or [Ctrl + Alt + ;], then 'Memory & Multiprocessing', check 'Render Multiple Frames Simultaneously', set 'CPUs reserved for other applications' to '0' and 'RAM allocation per background CPU' to anything you have available. Higher values, equal faster render time. Hope this helped!

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Walter SoykaRe: Render Bottle-necking!
by on Feb 12, 2014 at 3:38:34 pm

[Shane Smiskol] "check 'Render Multiple Frames Simultaneously', set 'CPUs reserved for other applications' to '0' and'RAM allocation per background CPU' to anything you have available. Higher values, equal faster render time."

This is not necessarily true. Setting Memory & Multiprocessing settings too aggressively can actually cause worse performance than not using multiprocessing at all.

The multiprocessing feature works by launching multiple copies of the renderer, up to one per CPU core, in order to render multiple frames at the same time. By setting "CPUs reserved for other applications" to 0, you risk overscheduling the CPU -- that is, not leaving enough CPU headroom for all the background tasks that the OS is trying to take care of.

Setting "RAM reserved for other applications" too low can cause memory starvation, where background tasks don't have enough RAM to work and where the system has to swap RAM back and forth to disk.

On a quad-core system without hyperthreading, I generally recommend first leaving at least 1 CPU available to other applications. I systems with hyperthreading, I usually start with half the number of CPUs. I generally recommend reserving at least one quarter of total system RAM for other apps.

Each instance of the renderer requires its own RAM, both for working and for layer caching, and the "RAM allocation per background CPU" setting controls this. Setting this too low can cause the render instances to run out of RAM and may force Ae to stop multiprocessing and fall back to single-instance foreground rendering. Setting this too high will eat up system RAM unnecessarily, reducing the amount of RAM available to other applications and potentially reducing the number of simultaneous instances of the Ae renderer you can run.

Some comps will benefit from more CPU more than they'd benefit from more RAM, and others may benefit more from more RAM than more CPUs, so these parameters require some juggling.

Some more good reading on these settings here:

And good tips here, too:

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events

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Mike BlutsteinRe: Render Bottle-necking!
by on Feb 16, 2014 at 9:12:56 am

Thank you for all the advice. I have tried multiple suggestions, but to no avail.

I am doing a small project, 1 Adjustment layer, 1 greenscreen shot with some keying and light wrap, a little bit of CC with Curves, a background stock footage layer, 2 lights and 1 camera zooming on slowly.

This entire thing is only 8 seconds long, yet still takes me 30 minutes to render. That is all well and good, but it is only using 5% of my total RAM and like 10% of my cpu. This truly baffles me!

Does this make any sense to you?

PS. Side note. I used BG renderer and it did the entire project in 6 minutes. However it gave me all photoshop files, when I need a loseless video file instead. Is there an easy way to convert all those little pictures to an actual video and look normal?


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