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Running an iMac Pro 10 core, 64GB Ram and 16GB Vega, MacOS 10.14.6. iStat menu (v6.40) is showing a consistent GPU Memory usage between 90% and 100% after I have been using the computer for awhile.

I close out of all programs and the memory does not seem to be released. The only thing that does it is to restart the system.

1) Why is the system not releasing the GPU memory? and 2) Can I do a manual release to free it up somehow?

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There has often been problems with AMD based GPUs and their reporting of video memory usage in iStat Menu. This has in the past been for example always reporting 100% usage, always reporting a climbing usage, etc.

If you haven't got any performance degradation, and your computer usage really isn't affected by this - I would just ignore the readout.

There's no tool to do a manual release - it doesn't really make sense. If the VRAM is actually in use, "manually releasing" it would make programs crash or behave unpredictable - nobody wants that.

If you really want you could probably lower the VRAM usage by logging out, or by killing WindowServer in its entirety. There's just no real reason to do so - unless you're experiencing a performance degradation, and then it would be better to analyze that specifically.

  • Thanks for sharing that. I'll post a few observations as an answer as it may be helpful to others. – hwp08 Nov 6 '19 at 22:38
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I have found the answer to actually be 'yes' you can release (flush) the VRAM. Here's what worked for me:

I have a hot corner (MacOS) set to turn the display off, and when I activate it, even just for a few moments, my GPU usage goes down to near zero once it comes back on -> not surprising since it’s off, BUT it continues to stay low as I go back to browsing around Chrome that stayed open, and other programs.

And keep in mind I’m pushing the VRAM with about 100 tabs open in Chrome that have many videos ready to play in the tabs.

So it seems the VRAM is released or flushed as the display is off but still remains low when using programs again. It’s almost as if it simply keeps things buffered as long as it thinks it needs it, which makes sense.

I often use large comps with big textures in Adobe After Effects, and that eats up all 16GB of VRAM no problem, so I know it’s there to be used, but the problem comes when I need AFX to use the GPU but it’s locked up in other apps where I can’t easily distinguish which one is using it.

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