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Addressing Performance/FPS Issues


Cameron
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Captains,

In the days since release of the Hot Start Challenger 650 there have been concerns that Gizmo and even the Challenger 650 plugins were causing a major performance impact. We went investigating this, and even got Laminar Research involved to understand what was happening under the hood of X-Plane to try and sort this out.

As it turns out, Gizmo is NOT the source of problems, and neither is the 650 plugin; not directly, anyhow. What's happening is somewhat complicated, but I'll do my best to be descriptive, yet brief.

X-Plane is programmed to use up all of your CPU cores in order to try and attain higher frame rates. In doing so, there's some major texture paging going on. The problem here is that it leaves almost no room for the Challenger to get its CPU operations done in the process, and mixed with a ton of texture paging, everything goes bust and tasks get stuck in a queue where X-Plane drastically slows down, things pause/stutter, and the experience becomes abysmal. If you happen to have your Plugin Manager open in X-Plane while this happens it will present itself as if Gizmo or the Challenger are using up an insane amount of performance, but this is actually just a mean trick when looking at it from a user perspective. X-Plane slows down so much that it LOOKS like our plugins are to blame as their tasks are not yet performed while X-Plane does other things. 

Before I go further, I should note, this is NOT applicable to everyone! Most customers here seem to have a great CPU/GPU combination that can handle all of this, but if you're one of the people on the struggling end of the spectrum, you'll want to keep reading this post!

Version 1.1.0 of the Challenger 650 introduces a new installer that has a selection for GPUs with more or less than 6GB so we can best optimize your install for you. This will help with some of the VRAM/texture paging operations.

That said, there's still more to the puzzle. Because X-Plane is using all the cores/threads on your CPU, it is not saving "room" for the Challenger 650 to do its operations efficiently and the CPU becomes oversubscribed. Laminar Research is likely to fix this issue for developers at a later date after X-Plane 12, so in the meantime we have a workaround to use that Laminar has sanctioned to give out to those affected.

 

If you are affected by this issue, please do the following (this is for Windows users, as the issue seems most prevalent with Vulkan):

1. First, find X-Plane's application and create a shortcut so that we can create parameters. Right click on X-Plane > New > Shortcut

2. Right-click on your shortcut, and select Properties on its contextual menu to open the shortcut's Properties window.

3. The shortcut's Properties window is the place where you can add command-line parameters for that shortcut. Select the Shortcut tab and look for the Target field.

4. You will see a place that has the path to X-Plane labelled Target. X-Plane's path will be in quotes. At the end of the quotes, make sure there is a space after the quotes, then type/paste: --num_workers=n  <==Replace the red 'n' with two less CPU cores/threads than your CPU has. As an example, if you have a 6 physical core + 6 virtual core CPU (known as Hyper-threading for Intel, SMT for AMD) for a total of 12 threads, you should put the number 10 in place of the red 'n'. Also be sure you have the TWO hyphens/dashes in front of 'num_workers'!

5. You can now rename this shortcut to something like Challenger 650 if you like. That way you can just click this one when you know you'll be flying the Challenger.

If you are unsure how many CPU cores/threads your CPU has, go into your About Computer setting and Google your CPU model number to find out. Be sure to use the total number with Hyper-threading/SMT as your starting point!

We know this is a bit unorthodox, but we're doing our best to make whatever solutions we can for as many people as possible. Hopefully this makes your flying more enjoyable!

Edited by Pils
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On 1/21/2022 at 4:54 PM, Cameron said:

--num_workers=n

I believe X-Plane doesn’t count its main thread in this value so that should be considered if necessary to free up additional processors for other uses, including an aircraft’s multi-threaded plugins.

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15 minutes ago, FarFoune59000 said:

Hello, 

even after applying these parameters. The brutal FPS drops (38/40  -> 7/5) are still present. It really hurts the experience with this beautiful plane.

I thought future updates would fix this problem...

Regards, 

 

On 4/4/2022 at 9:23 AM, Cameron said:

X-Plane 12 will likely have a way for authors work through this. For X-Plane 11, this will always be a thing.

As Cameron says above, the only update that’s potentially going to help is X-Plane 12, and that’s still theoretical. (Unless you’re talking specifically about the FBO van.)

Edited by Pils
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