TR Forums

I try to keep my system operating efficiently so I was surprised to get prefetch files for programs I had used 1 day ago or even 2 days ago. I thought the purpose of prefetch was to speed things up. The computer is shut down each evening so this data can't be sitting in memory. Would it be from the pagefile.sys?

The concept is that if you used a program yesterday, you're at least somewhat likely to use it again today. I'm not a big fan of this particular type of "optimization", but for certain usage patterns it can help. If the pre-fetching can be done in an unobtrusive way, it's "mostly harmless".

I forgot to add what annoyed me today. The prefetch was for Windows built in calculator.

ThatStupidCat wrote:

I forgot to add what annoyed me today.  The prefetch was for Windows built in calculator.    :x  :roll:  

Are you referring to the Prefetch folder under the Windows folder?

Edit: It looks like Windows did background maintenance on the prefetch folder since some of those I haven't touched recently but it shows date modified for today.

ThatStupidCat wrote:

I forgot to add what annoyed me today. The prefetch was for Windows built in calculator.

At least that should be small, so it is presumably "lost in the noise"!

It might be. I'll look next time they show up.

ThatStupidCat wrote:

It might be. I'll look next time they show up.

Technically that folder is off limits to non-administrators unless you give it permission to view the prefetch folder.
Nothing to mess with in that folder btw as Ryu would point out.

We're enthusiasts. We mess with the "no user serviceable parts inside" stuff. Some of us even do it at our day jobs.

just brew it! wrote:

We're enthusiasts. We mess with the "no user serviceable parts inside" stuff. Some of us even do it at our day jobs.

On equipment we're not supposed to be "servicing" in some cases.

Superfetch is not the insanely dumb monster it was in Vista when it was introduced.

If you want to, go to services control panel (services.msc) and disable "Superfetch". Dont really know what it does in Win 10, but i didnt even know it still existed. Though i always have fastboot disabled as default too.

blahsaysblah wrote:

Superfetch is not the insanely dumb monster it was in Vista when it was introduced.

If you want to, go to services control panel (services.msc) and disable "Superfetch". Dont really know what it does in Win 10, but i didnt even know it still existed. Though i always have fastboot disabled as default too.

Pretty sure the prefetch folder plus SuperFetch are responsible for pre-fetching, and filling the disk cache in RAM similar to how Android fills free RAM by loading Apps it anticipates your likely to use. Also doesn't SuperFetch work along side the ReadyBoost service?

So the issue was when it was introduce in Vista, it was too dumb. Lets say you played game X every day. After a few days, every time you started your PC, it would preload that huge game into memory for you(including its read only data cache/levels/textures). Great if that was all you did, but horrible the first time you wanted to do something else. Switched to Vista on launch day...

Very neutered in Win 7 because when it was wrong,... I was a little sad to not boot up PC and have it work hard getting favorite game all loaded up for its overlord but it was programmed as a dog i guess. Only if they had programmed a cat.

My experience is that if you can afford to have a decent SSD and decent amount of RAM, all these features are pretty much junk due to death of HDD/random IO latency and increase in RAM capacity for regular users.

Same with Fastboot. All the random problems it occasionally causes is not really worth the few seconds in the morning.

It's better on than off.

It also really isn't worth messing with.  It only applies to unused RAM and RAM will be freed as soon as it is needed.

You bought all that nice RAM, the least you can do is see it put to good use.

RAM drive > SSD

You guys worried about stuff like this would freak out in Linux.

http://www.linuxatemyram.com/

I've seen Windows' implementation slow stuff down pretty badly on occasion (though they seem to be doing much better these days). I've never seen Linux disk caching interfere with anything, and I both have swappiness left at 85 and regularly hit situations where it might be tempted to swap instead of evicting. I hear OS X / MacOS is the one with real trouble, though I haven't used it enough to say.

The key variable seems to be how willing the OS is to evict disk cache when the RAM is needed for something else. I don't remember details, but I remember being exasperated with Win7 circa 2011 for swapping like crazy while I was only trying to use <2 GB of 4 (seen across multiple machines).

Ryu Connor wrote:

You guys worried about stuff like this would freak out in Linux.

http://www.linuxatemyram.com/

Not me but I was wondering about this threads purpose. No offense intended to you ThatStupidCat.

No offense taken. Just wondering why the heck would windows want to prefetch/superfetch windows calculator especially 1 or 2 days AFTER I use the program. Seems pointless. I've seen other prefetch files pop later as well. Seems pointless.

Then I wonder where do they store these before they become a prefetch file. I know it's not in memory since that gets wiped after a reboot. So only logical place is the pagefile.sys which means I can stop it if I wipe out the pagefile.sys at each shutdown (see group policy). But this slows down the shutdown by a lot so it's not worth the hassle.

I turned on the delete the pagefile.sys at logout and was surprised to get a prefetch file a program that was uninstalled and deleted the prior week. Went to the directory and BAM there's a gazillion of them. That solves that. Prefetch files are not stored in the pagefile but for some reason I could not see the prefetch. Anyway I just want to close this out. I disabled the delete the pagefile.sys and leaving things alone. But from googling, the prefetch is a pretty good place to do some forensics stuff especially if you get hit with a malware.