Pre fetch

  • Thread starter Thread starter Spikey
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Spikey

Could someone give me a simple explanation of its function please?

If it isnt working properly is there a fix?

Thanks.
 
Prefetch sets up to align frequently used programs files in a outer
section of the drive to provide faster loading. Now what makes you
believe it isn't working properly?
 
Spikey said:
Could someone give me a simple explanation of its function please?

If it isnt working properly is there a fix?
Click to expand...

The files in the Prefetch folder are data files related to enhancing the
speed at which applications start. Windows XP Professional monitors the
files that are used when the computer starts and when you start
applications. By monitoring these files, Windows XP Professional can
prefetch them. Prefetching data is the process whereby data that is
expected to be requested is read ahead into the cache. Prefetching boot
files and applications decreases the time needed to start Windows XP
Professional and start applications.

You will have to explain what you mean by "isn't working" and what makes
you think it isn't working.

Malke
 
From: (e-mail address removed)
Subject: Re: Pre fetch
Newsgroups: microsoft.public.windowsxp.general
References: <uje#[email protected]> <#D0bP#[email protected]>
Organization: RadixNet Internet Services

Things that can cause prefetch to not work completely:

1) Task Scheduler Service is not running - req'd to monitor the
application loading process and create the .pf files. if the .pf files
have an old date then they are not being updated.

the .pf file for an application is examined at its launch time, in an
effort to order the disk fetch requests optimally to speed app launch (and
booting too). if the defrag (below) is also done then these fetches will
be contiguous, causing even more of a loading boost.

2) The machine must "go idle" for the prefetch logic to perform parts 2
and 3 of the optimization. Part 2 involves examining the .pf files and
producing a layout.ini file; at the same time old/invalid .pf files are
deleted. Part 3 involves using the info in the layout.ini file to do a
"boot optimize" type of defrag; this is a quickie defrag that moves all
the files ID'd in layout.ini to a contiguous defragmented area of the
drive, to allow them to load faster.

You can force the "idle processing" to take place via this cmd line:

%windir%\system32\rundll32.exe advapi32.dll,ProcessIdleTasks

[Amoung other idle things, like creating a System Restore point] this
will cause the layout.ini to be updated.

_IF_ the registry key allows it (see below), it will ALSO kick off the
boot time defrag; you can do that manually by this cmd line:

defrag -b C: [or whatever drive letter].

the reg key is:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\
OptimalLayout\EnableAutoLayout

0 = no
1 = yes [default]

This key is sometimes set to 0 by 3rd party defragers, if they take
over the optimize defrag process on their own. [TweakUI has a setting for
this key, under General | optimize HD when idle].

For the prefetch feature to have max effect you need all 3 things to
happen, and by default they will every few days if the machine goes idle.

Note System Restore points also only get made if the machine goes idle.
That's one good reason to make a shortcut to the idle-process cmd above,
and use it occasionally to ensure you're making restore points (if you're
the type of user that turns on the pc, works for a bit and then turns it
off, you may unknowingly not be making restore points!).
 
Malke said:
You will have to explain what you mean by "isn't working" and what makes
you think it isn't working.
Click to expand...

Thanks for replying Malke and Bob I..

I've been having a java rte problem. Even with the latest version once
installed I get a noticeable lag when opening IE pages with java content.
I've uninstalled as its unbearable (to me).

I've updated everything possible, tidied, deleted unecessaries and checked
all installed applications for reported problems/errors and come up blank.

I get a couple of hits on search engines with others with a similar IE lag
after java rte install. Both point to forums with no solutions. I've drawn
a blank on java groups and with sun java themselves.

I wondered if somehow prefetch was involved as I would have expected the
time lage to reduce the more java pages I opened.
 
That's not likely related to Prefetch. Are you running 512 memory, or is
there significant drive access related to the program loading? I would
lean to insufficient real memory.
 
Bob I said:
That's not likely related to Prefetch. Are you running 512 memory, or is
there significant drive access related to the program loading? I would
lean to insufficient real memory.
Click to expand...

512 with about 6Gb free on the hard drive.
 
Humm, just guessing now. Are you running anti-malware programs that may
be playing against the java? Any indication in task manager as to whats
happening?
 
Bob I said:
Humm, just guessing now. Are you running anti-malware programs that may be
playing against the java?
Click to expand...

Just Spybot and Adaware plus the windows removal tool monthly (from windows
update).
 
Thank you, I need a point in the right direction somtimes.

It was already set to automatic.

:o)
 
Prefetching boot
files and applications decreases the time needed to start Windows XP
Professional and start applications.
Click to expand...

Shouldn't that be, "increases the time needed to start Windows XP
Professional?" If you are prefetching things, that just means that there
are that many MORE things loading at startup. I can't see where an increase
in speed would be possible by loading more items.
 
FeMaster said:
Shouldn't that be, "increases the time needed to start Windows XP
Professional?" If you are prefetching things, that just means that there
are that many MORE things loading at startup. I can't see where an increase
in speed would be possible by loading more items.
Click to expand...


you can set the prefetch in the registry to either 1,2, or 3. this lets
the prefetch either only prefetch the startup programs and no more, do
nothing at all or prefetch the used programs while running. With the
last it can keep growing and slow the computer down. You can delete the
contents of the prefetch which will help with speed but it will rebuild
itself. Never delete the prefetch itself. I do not at this time remember
which value(1,2,3) does which but MS knowledge base will tell you or do
a google search. I have mine to only prefetch the startup which keeps it
from growing. I believe my machine does startup faster. I do not see a
slow down in the used programs starting up, but I think that has to do
with how you have your machine set up. Or if there is a slow down the
trade off is not enough for me to notice.
 
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