In the first of two articles from Michael Carnes the man behind Exponential Audio, Michael suggests we should not pay too much attention to the System Usage Meter in Pro Tools. Over to you Michael…

In the course of preparing another article, I realized it was time to eliminate the notion that the Pro Tools System Usage Meter was an accurate representation of what’s going on in your system. Let’s take a look at the meter as we know it…

in this example, to the right, the computer is a 2019 16-core Mac Pro 7,1.  The meter shows the 16 cores as 32 virtual cores since this machine supports hyper-threading.

From the display, we can’t really tell how this maps onto physical cores.  Are cores #1 and #2 part of the same physical core?  Or would that be core #1 and core #17?  It’s not at all clear, but it’s a secondary problem. 

The real issue is that familiar bump in the middle. No matter what you’re doing, activity seems to ramp up in those middle cores. 

The fact is that it doesn’t. Not really.  As an Avid Development Partner, I posed this question to a principal Pro Tools developer a few years back, and he explained that this display was a composite of some sort and showed some additional information useful for internal analysis. However, he agreed that although it was pretty to look at, it didn’t tell the full story. 

That’s the bad news. The good news is that your operating system has the tools for that. I’ll use MacOS for this explanation, but there are similar tools in Windows.

Look for the Activity Monitor app in the Utilities folder in the Applications folder.  When you run it, the window that is likely to appear will look something like this…

It’s showing you all of the processes running in your computer sorted by CPU usage but you can look at this data lots of different ways.  This image was taken at exactly the same time as the Pro Tools System Usage meter above.  You can see that Pro Tools is using 528% of a CPU.  In other words, it’s using a little more than 5 cores worth of CPU power.  It’s not telling us how the processing is spread across actual physical cores, but we have another view that really gets us where we need to be:

In the Window menu, you’ll see the CPU History option. When selected, this shows us the maximum load for each core over a period of time.  In this case, each little vertical bar shows us 5 seconds but you can adjust that down to 1 second.

This image was also taken at the very same time as the previous two, so it shows us the maximum load on each core in the couple of minutes before the screengrab. 

The left and right columns represent the two virtual cores of each physical core.  

The fact that there’s so little stuff going on in the right column means that only one virtual core is in use.  This isn’t good or bad: it’s related to the type of process going on and whether or not one virtual core may be blocked waiting for a resource.

I did some measurements a few years back and found that fully-involved hyper-threading only gave about a 30% performance boost.  That’s nothing to sniff at, but it’s not huge.

Core 1 and Core 2 represent the first physical core.  Core 3 and Core 4 are the next physical core and so on. 

You can see that there’s a little hyper-threading going on, but not a lot.

We also see a little more load in the first 8 physical cores.  I suspect that the Dolby Renderer is running in those cores, with Pro Tools layered pretty equally across all 16 physical cores.

So where’s the lump in the middle that appears on the Pro Tools meter?  The fact is that it isn’t there. 

If you’re running a loaded-down session and begin moving tracks around to even out the load, you shouldn’t have leveling the lump in the Pro Tools System Usage window as a goal. 

Instead, look at the meter in Activity Monitor.  The truth is that Pro Tools does a really good job of load-balancing across available cores.  It’s a pity that their own meter makes it appear they don’t.

What’s Next?

In the next article, I will be demonstrating the power available in the new Mac Pro 7,1 compared to a Mac Pro 6,1 Trashcan with the same Pro Tools Dolby Atmos session using many VIs and the Dolby Renderer using Apple’s Activity Monitor rather than the Pro Tools System Usage meter to show what is going on.