Linked by Thom Holwerda on Mon 11th May 2009 20:43 UTC
Windows SuperFetch is a technology in Windows Vista and onwards that is often misunderstood. I decided to delve into this technology to see what it is all about, and to dispel some of the myths surrounding this feature.
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RE: super fetch and assumptions
by Thom_Holwerda on Mon 11th May 2009 22:01 UTC in reply to "super fetch and assumptions"
Thom_Holwerda
Member since:
2005-06-29

As a real world example, I run computer labs at a university. We moved to Vista this past year. Computer performance got worse as the day goes on. Why? Different users use different apps. And the computer can't make any long term predictions. So everytime a user does something, the system has to unload what is in memory and then load something new. This results in lots of disk thrashing and horrible performance.


Couldn't this be solved by using multiple accounts? I'm actually researching this now, because it dawned on me that if SuperFetch data is stored in /Windows/Prefetch, how is it multi-user aware?

Maybe it uses attributes or ACLs to tie .pf files to user accounts? I really have no idea, and Google isn't helpful either. Maybe PlatformAgnostic (you there?) or some of the other Windows NT experts in here can help us out...?

Reply Parent Score: 1

Vide Member since:
2006-02-17

mmmh.. why SuperFetch (or any other similiar application) should care about different users? I mean, it is focused towards programs. Word loads the same exe and the same dlls when launched by mum or dad or joe the plumber, so cached memory is still the same.

Reply Parent Score: 1

hufman Member since:
2008-10-11

The PreFetch directory can be shared across accounts, because it merely contains the list of what libraries need to be loaded by each application. The user's profile of often-used applications doesn't live in there, I don't think.

Reply Parent Score: 1

kerframil Member since:
2005-07-13

Couldn't this be solved by using multiple accounts? I'm actually researching this now, because it dawned on me that if SuperFetch data is stored in /Windows/Prefetch, how is it multi-user aware?

It's really quite simple. The SID of the user account is referenced in the filename (depicted here as %SID%):

AgGlUAD_P_%SID%.db
AgGlUAD_S_%SID%.db

Also, the .pf files are nothing new. These are trace files that are used by the cache manager to improve application launch times through strategic prefetching. This is a feature that was introduced in XP and, as far as I'm aware, has nothing to do with SuperFetch. The windowsitpro.com site has a fairly detailed article about it:

http://tinyurl.com/9qhwso

EDIT: I didn't notice at the time of writing that the distinction between prefetch and superfetch is elaborated upon to some extent in later comments. Still, the above article goes into rather more detail.

Edited 2009-05-16 05:24 UTC

Reply Parent Score: 1