I get a lot of pushback on that older article from people who are absolutely convinced the System Idle Process is somehow evil and must be eradicated simply because their computer is slow and “System Idle Process” is at the top of the CPU usage list.
They are wrong.
System idle is benign. The CPU has to do something 100% of the time. When it has nothing to do for you or the system, it’s assigned the idle task to while away the time. It’s the CPU equivalent of twiddling your thumbs, waiting for something to do.
So why is your system slow as molasses?
Well, I’ll give you one hint: the CPU is not the only thing in your computer that affects its speed.
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The CPU, or Central Processing Unit, is often referred to as the brain of your computer. It runs programs, which are sequences of instructions that cause it to perform calculations, and generally tells the rest of the computer what to do.
We often place a lot of importance on the speed of our CPU. A faster CPU performs those instructions faster and gets us faster results. Similarly, if we run too many programs at once, all making demands on the CPU, the system gets slow. The CPU simply can’t execute those instructions fast enough to keep up with everything we’re asking of it.
That’s so common, in fact, that whenever a system slows down, people automatically assume it must be due to the CPU being overloaded — even if the Task Manager shows that the CPU is actually spending most of its time doing absolutely nothing.
I’ll put it as clearly as I can: if the CPU is mostly idle — spending the majority of its time in the “System Idle Process” — then the CPU is not slowing your system down. The System Idle Process is not “hogging” your machine. It just isn’t.
Fine, so it’s not the System Idle Process; then what the heck is it?
It can be many, many things, almost all related to your hardware.
By far the most common culprit is your disk. If your disk drive is continuously active while the CPU is idling, then whatever is using the disk is likely to be making your system slow.
And the most common cause of that? Not having enough RAM for all the programs you’re attempting to run.
When programs request more RAM than your system has, Windows uses what’s called “virtual memory” to satisfy the request. Through a complex process, it uses your hard disk in the form of a “swap” or “paging” file to make it look like your machine has more RAM than it really does.
As fast as they are, hard disks — even SSDs — are slow compared to RAM. That means these disk accesses take time — sometimes noticeable time. In fact, if there’s enough virtual memory activity, your system can slow to a crawl as all the software attempting to run causes memory to be swapped in and out repeatedly.
When this type of virtual memory “thrashing”, as it’s called, is going on, it’s not at all uncommon for the CPU to spend the majority of its time waiting for the hard drive to read or write the memory being swapped in and out.
The CPU is mostly idle, but your system is slow as molasses because it is spending all its time waiting for the hard disk.
The solution depends on your situation, of course.
- Don’t run as many programs at the same time.
- Don’t run as many programs that require a lot of memory.
- Don’t do things that require a lot of memory — perhaps editing a huge picture or video, for example.
- Keep your software up-to-date to get fixes for freshly discovered “memory leaks”.
- Consider adding RAM if your system supports it.
And while hard disk thrashing is perhaps the most common scenario that can lead to this symptom, it’s certainly not the only one.
The CPU is innocent
The bottom line is that you can stop blaming the System Idle Process for hogging your machine — it’s not. In fact, if it looks like it is — if the System Idle Process is using lots of CPU while you experience a performance problem — that’s a clear sign to look somewhere else for the source of your computer’s troubles.
(I hate to have to say this, but experience shows what will happen now. Comments to this article that continue to insist that the SIP is the problem will be deleted. You clearly didn’t read the article.)
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