Solved To Prefetch, or not to Prefetch?

TairikuOkami · Jan 3, 2023

To waste RAM or not to waste RAM?

Prefetch is still one of the lead causes of leaked RAM/CPU.

[Fixed] SysMain Causing High CPU And Memory Usage In Windows 11

In this article, we will see how to fix the SysMain service causing High CPU and Memory usage in Windows 11. If you have recently switched to Windows 11, you

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jimbo45 · Jan 3, 2023

Hi folks
Prefetch is a complex algorithm which exists in all modern OS'es and is often far more useful than you think. What it does is by "learning" what the user runs most frequently and then puts this into storage so when the application is run it's available almost instantly. You need a decent amount of RAM of course and it's "dynamic". Large applications with sluggish start up times obviously will benefit more than small fast apps.

Some indication of performance can often be noticed after clean installing a new Windows system. You'll probably see overall performance improve after a few logons as the prefetch algorithm starts using data it has collected and it refines as it goes along.

On multi user systems like servers etc it makes a lot of sense.

Some of those articles about CPU / memory leak etc have nothing to do with the theoretical aspects of prefetch. If those things happen that's because of defects in the OS itself. High CPU usage also is usually caused (unless you are running a load of complex mathematical models and a load of floating point apps) by either lack of RAM for the workload or incredibly poor Disk I/O subsystems (or both). On modern machines the graphic functions are often handled via a separate graphic processor / co-processor.

Cheers
jimbo

TM21 · Jan 3, 2023

"Scanning and backing up prefetch data will have no noticeable impact on time or storage."

Au contraire Mon Fraire!

Repeatedly scanning thousands of garbage files on a hard drive, shortens the life of the drive. And it also lengthens the time of the scan too.
It can also lengthen the time it takes for the system to boot up, because all files have to be read and directories formed.
Then if you do a backup, the garbage files swell the size of the backup.
Maybe a better example for you, would be, "do you take out the garbage in your house, or just stack it in a corner?".

You're whole precept that garbage should be left alone because it won't hurt anything is amateurish, juvenile and very poor advice to the new PC operators, that might be reading this forum.

Personally, I have just shut OFF Prefetch on this PC, and so far I see no ill effects. "Minus krud is cool!"

DigitalGoat · Jan 3, 2023

TechnoMage2021 said:
"Scanning and backing up prefetch data will have no noticeable impact on time or storage."

Au contraire Mon Fraire!

Repeatedly scanning thousands of garbage files on a hard drive, shortens the life of the drive. And it also lengthens the time of the scan too.
It can also lengthen the time it takes for the system to boot up, because all files have to be read and directories formed.
Then if you do a backup, the garbage files swell the size of the backup.
Maybe a better example for you, would be, "do you take out the garbage in your house, or just stack it in a corner?".

You're whole precept that garbage should be left alone because it won't hurt anything is amateurish, juvenile and very poor advice to the new PC operators, that might be reading this forum.

Personally, I have just shut OFF Prefetch on this PC, and so far I see no ill effects. "Minus krud is cool!"

You seem to not realise that what you consider garbage Windows does not.
What is this 'all files have to be scanned, read and directories formed' you are talking about? When is this supposed to happen, at boot up? Doesn't happen that way. Windows only reads the files needed for boot, when booting, not the whole disk.
An anti-virus app will exclude certain file types and directories when scanning.
Most backup apps will also exclude certain files and directories to keep the size of the backup reduced, these files and directories will be re created by Windows when it is restored, if needed.
Encouraging 'new' PC operators to switch off parts of the OS and delete files without fully understanding their use is hardly good advice.
You seem to need your tinfoil hat loosening a little bit.

jimbo45 · Jan 3, 2023

Some here obviously don't understand either what prefetch is or how it works. It's nothing to do with scanning 1000's of files etc etc. Some people also confuse "Prefetch" with "Indexing" which is a different ball game.

99% of people should really leave a lot of these "internal parts" of the Windows OS alone until they have some idea (hopefully not gleaned from terrible sites like Reddit) of how the OS works -- and even then it's often better just to leave Windows to manage itself.

If you want to try out new things for "Learning" then start by using a VM as you can fiddle around quite a lot and if it all goes wrong just delete the VM and start again. If you can't manage VM's then you shouldn't be tinkering around with parts of the Windows kernel in any case

Cheers
jimbo

Solved To Prefetch, or not to Prefetch?

TairikuOkami

Microsoft 365 Basic

[Fixed] SysMain Causing High CPU And Memory Usage In Windows 11

My Computer

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jimbo45

Well-known member

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TM21

Banned

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DigitalGoat

Well-known member

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jimbo45

Well-known member

My Computer

System One

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