High idle cpu even though an app is using 100% and struggling

Question

Level 1

8 points

High idle cpu even though an app is using 100% and struggling

Hi everyone,

I am currently using a MacBook Pro and an iMac to handle a lot of vector images (trying to arrange them in a big grid). I do this using Inkscape, but when it comes to image analysis I also use Mathematica.

I have noticed a strange behaviour on both machines, with both software. Even though the apps are making use of 100% of cpu (not at the same time), the idle cpu is almost always around 74%. The Mackbook Pro has two cores but I am seeing four columns in CPU usage or history, due to hyperthreading. The first and third column are half way busy, like a little above 50%, and the other two are almost empty (that's when the apps are shown to be using 100% cpu individually).

The only time the idle cpu drops below 50% is when I turn on the machines, i.e. when the system needs more cpu. The overall cpu LOAD in activity monitor has a few spikes then, but when the apps I am using require more power, it never goes above 50% (the load).

I have spoken to Apple support but they couldn't find some other relevant report of this issue. Please note that I am about to take the MacBook Pro for service, because of an email I received saying that the SSDs of this series have been found to be faulty. So when it comes to the laptop, this could be related to this issue. But how about the iMac? It shows the same behaviour and I doubt there's something wrong with its SSD too.

Any suggestions would be greatly appreciated.

Legnahn

=============================

Model Name: MacBook Pro

Model Identifier: MacBookPro14,1

Processor Name: Intel Core i5

Processor Speed: 2.3 GHz

Number of Processors: 1

Total Number of Cores: 2

L2 Cache (per Core): 256 KB

L3 Cache: 4 MB

Memory: 8 GB

MacBook Pro Retina (2015 and later)

Posted on Dec 20, 2018 2:08 AM

Reply

Answer 1

Top-ranking reply

Luis Sequeira1

Level 9

67,288 points

Dec 20, 2018 3:49 AM in response to legnahn

I don't see anything abnormal in what you describe. Your mac is running hundreds of processes at any given point in time, and the OS is responsible for distributing this load among the available cores.

Your mac has two physical cores. An application like Mathematica will spawn several concurrent threads at any point in time, and they may or may not all be assigned to the same core. So it is quite possible that the main calculation task be run in a thread on one core, and several others making use of another core - you really have no control over this (and have no reason to, anyway).

You may open Activity Monitor to get a better idea of what processes are using your CPU resources.

Reply

Answer 2

legnahn Author

Level 1

8 points

Dec 20, 2018 4:27 AM in response to Luis Sequeira1

Hi Luis and thanks for your reply.

The observations I described were made in Activity Monitor. There can definitely be something I don't know or understand here, but just to make sure, I am posting this screenshot of the situation I am trying to describe.

Thanks again,

Legnahn

Reply

Answer 3

Dec 20, 2018 5:13 AM in response to legnahn

100% in an application means one hundred percent of ONE CORE.

What you show is consistent with this - you are basically using 50% on one core, and 50% on another core:

If an app were using up all the resources it might inch closer to... 400%.

People sometimes wonder why an application does not push the CPU harder. The answer is that often the CPU is not the bottleneck. If an application is doing a lot of IO, then it may not be able to push the CPU to the highest, simply because it is waiting.

In fact the one thing a CPU does most is just that, waiting.

Reply

Answer 4

legnahn Author

Level 1

8 points

Dec 20, 2018 10:01 AM in response to BDAqua

BDAqua, here's the report, there is obviously information missing since I used the free version.

Also, it was way more than 5000 words so I took a screenshot of it. If you find it unreadable let me know.

Reply

Answer 5

legnahn Author

Level 1

8 points

Dec 20, 2018 4:56 AM in response to dialabrain

Thanks for your reply dialabrain.

This should probably point me in the right direction. It is true that Inkscape is not fully compatible with Macs, but I did not expect this to be happening with Mathematica as well. So I thought that something could be wrong and I, as "the user", am not given access to all the cpu my apps require.

Thanks again for your time,

Legnahn

Reply

Answer 6

legnahn Author

Level 1

8 points

Dec 20, 2018 5:52 AM in response to Luis Sequeira1

Hi there again Luis,

That makes sense. I also looked into some preferences regarding rendering in Inkscape, including number of threads, and even though I didn't see that making any difference in terms of cpu usage, which makes your point, I believe I have found ways to make the type of work I'm currently doing less agonising :)

Thanks once more,

Legnahn

Reply

Answer 7

BDAqua

Level 10

245,165 points

Dec 20, 2018 6:53 AM in response to legnahn

Post a report from this please...

EtreCheck is a simple little app to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to help people help you with your Mac.

http://www.etresoft.com/etrecheck

Reply

Answer 8

Dec 20, 2018 10:17 AM in response to legnahn

The report looks pretty clean to me.

I still can't see any problem. AFAICT, there is nothing wrong.

An application works according to how it is programmed.

Some applications may be able to use 16 cores to do one task, if there is enough parallelism and it is programmed to work that way, but if a task is mostly sequential and requires waiting for IO the CPU usage will far lower.

Reply

Answer 9

BDAqua

Level 10

245,165 points

Dec 20, 2018 10:26 AM in response to legnahn

Other processes 112.15 % (?) bothers me, & did you remove that file in cleanup that was the last thing in the pic?

You're also trying to do a lot with 1 2.3 GHz Intel Core i5 (i5-7360U) CPU: 2-core & only 8GB of RAM.

Reply

Answer 10

legnahn Author

Level 1

8 points

Dec 20, 2018 10:39 AM in response to BDAqua

"Other processes 112.15 % (?) bothers me"

Yes, that's Inkscape, and is what initiated my quest. I sort of thought that it was the limited use of cpu that made the app slow. And since I was seeing a lot of cpu being idle, I thought "why isn't it taking up more?" But like Luis said, "often the CPU is not the bottleneck" which brings us to what I'm trying to do with this machine and what you said.

I haven't removed the file yet, but I will.

Thanks BDAqua!

Reply