Prefetch is Supposed to Be Super Important for Performance, Right?

Hi -

This is just a fun topic for those of you out there that like this stuff. I had an idea about prefetch in good old xp that I have never heard mentioned. On the other hand I haven't looked lately. Here it is: Basically, you are limited to 128 files to be prefetched. Those files (eventually) are optimized on the hard drive and put in some sort of logical order. Now people will argue to the end of time whether prefetch folder should be cleared out periodically. Others say, no, files that are not used will be dropped eventually (when the 128 limit is reached, then add one, drop the least used (I guess)).

But....what about line item veto? a quick look in your prefetch folder will reveal that a very large percentage of them are not things you need to prefetch. Take for instance something that you install putting copies of the uninstaller it creates during the installation in prefetch. Yes, eventually it will drop out, however it's likely you have many of them and more on the way, so...do any of you ever just delete individual prefetch files on the basis of their names being things that don't need to load? I've been doing it a while. I don't have any way to measure the performance, and it would be hard to do at best. I'm sure you could use BootVis and get a little insight, but after all, prefetching pertinent programs could slow down boot up, but increase the performance of your applications. So I'm just doing it for fun to see what happens. Sound good to you?


-HandsOff

 

Hi HandsOff,
Recently I had some slow boot up problems and I just solved my problem by clearing my Prefetch folder.

Right now I am doing some testing. I am using this small free tool "Windows XP Prefetch Clean And Control" I set it to monitor the Boot file only and so far I didn't experience any slow boot up like before.

This tool ca be downloaded from here.

http://www.majorgeeks.com/download.php?det=2495

 

Oh, cool, then people are looking at weeding out the junk files. I didn't want to address other thoughts I had about it if it was a complete waste of time, but I had wondered the effect on startup when prefetch tries to prefetch something that has been deleted. I would not be surprised it keeps looking for a while. (an example being an installer for a specific program that is deleted after the completion of the installation).

I will definitely take a look at the program. It almost has to boost computer performance for someone like me who has the 128 slots full, and many of them probably will junk files of some kind. Thanks for the suggestion!


-HandsOff

 

Ace Utilities also offers to clean the PreFetch

 

I just turned Prefetch totally off long ago......Can't say I've even missed it



Cochise.

 

Maybe. Nevertheless, it makes no sense to turn it off or to manage it with a tool. Older entries are automatically removed after some time, and every 3 days the list of files and folders is reorganized by the Task Scheduler (that's one reason why one shouldn't turn that program off, either) and stores that list in the file c:\Windows\Prefetch\layout.ini. By the way: There are some defragmentation programs that don't take layout.ini into account - stay away from them as they counteract the prefetch mechanism.

A short description how prefetch works can be found on http://msdn.microsoft.com/msdnmag/issues/01/12/XPKernel/default.aspx

 

i dont turn off prefetch. it is essential in windows. it automatically delete old files.



thanks sir for this soft. i will try...

 

That's news to me....I see it as a troublesome piece of kit I can do without...I have better ways of ridding myself of old Files, without slowing my OS down...

Cochise.

 

Never noticed a bit of difference. Really just a "hot-rodded" Indexing Service. Another one which I always disable.

 

i depends on your taste on how you setup your windows. i know prefetch is important more in lower end pc like me. i know in a hi-end, you see no difference at all.

 

Do not know,do not care.Prefetch seems to be non important as you can read here. http://mywebpages.comcast.net/SupportCD/XPMyths.html

 

yup! i read that. as you can see the remark in cleaning the prefetch regularly is decreasing your performance. as i say it depends on your taste. i you have a hi-end pc (like a quad-core processor with 4gb of ram) you will not notice a difference in speed.

 

Yes, that's a good source, but unfortunately you didn't really read it. It doesn't say that prefetch is non-important but rather says that it doesn't make any sense to clean the prefetch folder and to apply other "tricks".

 

Exactly ThunderZ......I have indexing turned off as well...just another thing of many that are of no consequence.....


Cochise....Indexless in Indiana...

 

Great minds (or not) think alike.
With apologies to those who believe in "Prefetch", Indexing Service" and even Memory Managers, a question. What is one of the first things we do in an attempt to speed up our PC`s? We disable as many start-up programs and services as we can. We also (should) defrag regularly. I have yet to figure out how adding programs\services that start-up and run continually in the background causing fragmentation, as any program will, speeds up our system. My tower is no slouch for performance. However I did not build it to cater to the OS. I built it to run the after market apps. of my choosing and to perform the tasks I want. The OS, IMO, is just a necessary evil that ties them, hardware\software all together. Off my soapbox now.


TZ.......running bare bones in Boise......

 

Read the links in postings #6 and #11 and you can figure it out.

 

Have read them, does`t mean I agree with them. I`m not saying that it may not (seem) to work for some on some machines....just speaking from my personal experience.

 

thank you, thank you for starting this topic Handsoff! I was wondering why the hell my laptop would take 60 seconds to boot! I could literally start my laptop, go to the bathroom, wash my face, brush my teeth, and make it back in time to have the laptop ready to work.

thank you to Antarctica too for linking to that freeware program that cleans and disables prefetch, without that program I wouldn't know how to clean or disable the prefetch.


finally, thank you to cochise for recommending turning off that crap prefetch!

i learn something new, every single time i log on to check these boards! this is why wilderssecurity is my homepage.

rock on guys..........

 

If you prefer to change the registry instead of using software, you can find it here.
http://www.theeldergeek.com/prefetch_parameters_-_altering.htm

 

On the prefetch good or bad -

That one always stirs debate. If you leave your computer running start up time may not be an issue, but regardless of the theory of old files being thrown out and the layout.ini being sorted, that doesn't change the fact that XP was prefetching about 30 install and uninstall files for programs I had installed, and many other pieces of useless junk.

tlu - you might do well to actually open the folder and see is you can pick out 20 or thirty junk things that don't need to load. It would also be interesting to hear what your total number of prefetch files is. If it is under 128 i don't think the prefetcher will remove anything until such time as it does

if you do have 128 and 28 are junk, then I think the nextime something new is added, 1 out of the bad 27 are removed.

I'm a prime candidate to use prefetch, and I do. But I think there is room for a middle position of the actual computer user, not Microsoft, deciding what needs to be prefetched. I would think prefetch might not be good for a lot of laptop users. Like someone said.

I'll take my theory one step further. Since the prefetcher adds and deletes single entries, then it is very likely that there is no harm in taking entries out yourself. How could there be?


-HandsOff

 

If you delete the pf-files referring to the update.exe's of the latest Windows Update, there is indeed no harm since you won't execute them again. But that's not the decisive point. The question is: What do you gain if you delete these pf-files (except for a few KB's)

Again, read http://mywebpages.comcast.net/SupportCD/XPMyths.html and http://www.edbott.com/weblog/archives/000743.html . Cleaning the prefetch folder doesn't make any sense (even for laptops).

 

I understand Prefetch is probably useful but in my case it was not to gain a few
KB that I now control what I leave in Prefetch.

Before my computer would take like three minutes to boot and now it merely takes one minute. I have no explanation why this happend. And I made quite a few test, if I leave Windows to prefectch in normal mode it doesn't take long until my bootup problem is back. As soon as I leave it to Prefetch to monitor the Boot file only, the startup time is back to normal.

It may be some conflict with my applications I don't know, and in fact I don't care as long as I have no startup problems.

 

Ah, but that's just it. It is not the kb's gained that is the key benefit. If we can agree that prefetching speeds up applications, then at the risk of repeating myself the two larger benefits to to deleting (in my case about 40 that were useless) that I am saying I anticipate are:

1 - The start up time will be faster (or at least more well spent). Probably not a lot faster, but faster.

2- The 40 useless prefetches might be replaced more quickly by 40 legitimate ones.

3- We come to the issue of auditing. In my mind there is always a question of what is running and why. What is residing in memory and why. What is starting, what is loading by direction of some preferences other than mine.

4- What implications does a list of what I run and how often I run it say about me to someone harvesting information. Let me take a quick look...

Hmmmmmmm

- I can see the date I installed windows and the file system
- I can identify my firewall
- I can identify my Office program
- My media player
- My graphics editor
- baically, every security program that I run..
- What's worse is that it is strongly suggestive of what programs have access to the internet
- It names a program that I prefer not to repeat here.

Also nobody has mentioned the running debate about CCleaner and why it will be default clean "old pretch entries". This is actually what I would guess is the preformance option that suits someone like me the best. I just ran it, and aside from the two special case files it left the files accessed within the last 2 weeks. Surely anyone can see the sense in this! if you haven't run it in two weeks, then it doesn't need prefetching very much does it?

But back to the self-auditing part of my auditing. I was looking because I was just curious is something suspicious could be there. Is it possible for maleware to be imbedded in a prefetch file? I don't know! By I know it can't if it is not there!


-HandsOff


One thing I didn't mention was the age of some of the useless prefetches. My impression was that there were too many bad ones that were too old to make any kind of sense.

Another thing I didn't mention was the time frame involved in creating a prefetch folder with the full 128 items. Just on the face of it, if it takes 6 weeks to fill the quota, and some of them are still useless then it would appear that many if not most of these files do not justify a need to be prefetched

 

Cleaning the Prefetch folder is a Myth

Cleaning the Prefetch folder is a Myth:

http://mywebpages.comcast.net/SupportCD/XPMyths.html

The files are layed out consecutively on the HD automatically every 3 days after the sytem goes idle for more than 10 minutes by the disk defragmenter to further improve prefetching performance. You can manually force this sooner by doing the following:

Go to "Start", "Run", Type Rundll32.exe advapi32.dll,ProcessIdleTasks. This can take 10-15 minutes to run but no notification will be given when it is finished. You will notice increased Harddrive activity while it is running wait until this stops. When this is finished in the "Run" box Type defrag c: -b.

Yes you have Microsoft, the Windows Client Performance Team experts like Ed Bott, Mark Russinovich and everyone who understands how Windows XP Prefetching works (leave the folder alone) vs. all those who have no idea what they are talking about (clean the folder).

When the 128 limit is reached the folder will be cleared except for 32 of the most used prefetch files. Each prefetch file is assigned a value to determine this.

Irrelevant, those files do nothing but take up a small amount of disk space and will eventually be cleared. These files in NO WAY reduce performance, it is impossible if you understand how Windows XP Prefetching works. You are wasting your time deleting these files. All the files in the folder are not prefetched at Windows Boot. Only one file is prefetched at boot: NTOSBOOT-B00DFAAD.PF the other files are not referenced unless the associated application load is initiated.

It doesn't reference those files. So it does not reduce performance in ANY way.

No the program will REDUCE performance. Having 1 or 128 files is irrelevant Windows XP will boot in the exact same amount of time.

No it wasn't. You are assuming it is because you do not understand how it works and are guessing. It does not prefetch these files.

This is a waste of time and will do nothing but free up next to no disk space. In no way will performance be improved.

See you are guessing and that is the problem here.

It is good for everyone regardless of the speed or type of system they have.

I don't understand how you go from a question to a misinformed statement like this based on assumptions and guessing? There is no harm in removing unused entries but it will not improve performance and does nothing but clear up a ridiculously small amout of disk space and you waste your time.

Nope the Windows boot time will be identical with or without those files.

The speed at which they are replaced is irrelevant to you manually deleting them. Any new application launched will be prefetched ALWAYS, if the 128 limit is reached the folder is cleared to 32 prefetch files. You manually deleting any does not change this.

Prefetching is not the process of having something preloaded into memory. It is the process of OPTIMALLY loading something to memory. That is the point.

Huh? No one has access to that information except someone with local administrator acces to your PC. No one can "harvest" this information over the Internet.

It does not anymore. It defaulted originally because the author of the program had no idea how prefetchiing worked. Uncheck this and do not use this option. http://www.populartechnology.net/2005/10/ccleaner-cripples-application-load.html

No prefetch files are NOT executable. This is another ridiculous Myth spread by all the know-nothings who give malware removal advice.

Huh? Prefetch files are just used to optimally load an application. Unless the application changes such as installing a new version than there is no reason for the prefetch file to change. Regardless they are dynamically updated.

The time frame is irrelevant. It has to do with how many applications you load and when you load them. If you load 128 different applications in one hour then the folder is full in one hour, it it take you 3 years than the folder is full in three years. But again the unused ones are not prefetched until the associated application load is initiated.

 

This is bad advice and will REDUCE performance. There are many reasons you could of had a slow boot time and none of them had to do with Prefetching being enabled. Other bad "tweaking" advice comes to mind. When timing boot times it is critical to use a timing device like a stop watch and time from when you press power to the desktop. Setting this to only prefetch boot files will boot Windows in the exact same time as the default optimal setting only now ALL your applications will load slower.