Windows Prefetcher tips and info


Recommended Posts

The Windows Prefetcher Guide

One of the hidden features in Windows XP (only) is the prefetcher. It, quite simply, works to speed up the launch of applications by loading them before you access them. It primarily works by loading startup programs during the time windows is still booting so that when you enter your password, everything loads quickly. It also keeps a record of all programs launched and how much they are used to aid in allocating how much prefetching to which program.

Contrary to popular belief, it is not responsible for making windows boot as fast as it does. In fact, the prefetcher only makes that it longer, since with the prefetcher activated it uses that period of time to load the other stuff that's going to load. But this is still a good thing, as it is annoying to continue waiting for stuff to load after you enter your password. The prefetcher works to take all the loading to the windows boot logo stage to make everything else that requires your interaction faster.

The prefetcher has a file for each program that you run that, in part, records the amount of use. Logically, programs that are loaded often are prefetched more than programs that are not.

The prefetch files are located in %windir%\prefetch. That's C:\windows\prefetch for those who don't know. If you opened it now you would see a whole bunch of .pf files and one layout.ini file. All the .pf files are individual recoards of each program. The layout.ini file is a consolidation of all those programs and what they typically access, in order of priority.

The prefetcher requires scheduled tasks to work. If you have the service disabled or off, the prefetcher will not function.

Tweaking

Your prefetch folder is probably full of programs that you don't even have installed anymore, or only used once. If you want you can always delete everything in the folder. Doing so has no bad effects on the system except you will notice that the computer loads differently on reboot. After you delete everything, the prefetcher will start the process again from scratch.

You can tell the prefetcher if you want to monitor boot files, monitor applications, monitor both, or nothing, by either editing the registry. There are also programs that provide a user interface if editing the registry scares you.

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters]

For "enableprefetcher", 0=disabled;1=monitor application launch;2=monitor boot files;3=monitor both (default)

Note that there is no other value that will do anything other than 0-3. Higher numbers probably just turn it off.

Now lets say you want to have only certain applications prefetched. You can do this by setting the prefetcher to only monitor boot files and setting a special switch in the program shortcut: /prefetch:1 . This doesn't work for all programs, but it does work for firefox so I'll use that as my example. Right click the firefox shortcut, select properties, in the target box insert /prefetch:1 at the end. Alternatively you can set certain programs to not prefetch by adding /prefetch:0 .

post-38325-1118616837_thumb.jpg

Link to comment
https://www.neowin.net/forum/topic/331520-windows-prefetcher-tips-and-info/
Share on other sites

Good info.

Just a note. Certain programs won't accept the /prefetch:1 switch (such as Outlook). They'll take it as an actual switch and try to process it.

I'd also recommend completely turning off the prefetcher for systems with 128MB or possibly even 256MB of RAM. The more data that's being prefetched, the more memory that's being used up, and on low memory systems, it takes its toll.

Just a note. Certain programs won't accept the /prefetch:1 switch (such as Outlook). They'll take it as an actual switch and try to process it.

This doesn't work for all programs, but it does work for firefox so I'll use that as my example.

586055424[/snapback]

  • 2 weeks later...

The guy makes good points and adds to knowledge about how the prefetcher works.

Clearing out the prefetch folder every week doesn't increase performance. Heh, if you did that then you might as well turn it off.

I'm not sure about what he wrote with the /prefetch:# switch, but the proof is in the firefox quite frankly, as with that switch firefox loads in one second as opposed to about 15 seconds (but has the down side of increasing the time it takes to boot).

dont' quote me on this ..bu I think its under hkey local machine/system/current control set/control/session manager/memory managment/prefetchparameters and change the enableprefetcher to 0

Edited by warwagon
dont' quote me on this ..bu I think its under hkey local machine/system/current control set/control/session manager/memory managment/prefetchparameters and change the enableprefetcher to 0

586136441[/snapback]

holy.. geez, that's deep in the registry. Thanks

-_-"

Warwagon, IceDog, you are embarassing yourselves. The questions you asked can be answered right in the post I made.

586138975[/snapback]

yea I seen that after I posted my thanks.. DOH.. sorry bout that. I don't know how I missed it before. I did read your post though. :blush:

This topic is now closed to further replies.
  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Posts

    • My father still uses a programme written in dbase3. Still manages to work with a little help from dosbox. 
    • Microsoft hides these secret Windows 11 performance boost settings available on every PC by Sayan Sen Windows enthusiasts often look for ways to extract as much performance out of their systems as possible, and it's often the case that they try and do so while trying to minimize the heat and power consumption. This is especially relevant in the case of mobile Windows PCs since laptops and notebooks tend to get hot and management of that heat and power is harder in such a form factor. As such users often turn to techniques like under-volting which can be used to squeeze out the maximum capabilities of a chip while also maintaining lowered power levels. There are official apps from AMD and Intel with the likes of Ryzen Master and XTU (Extreme Tuning Utility). While these are quite handy, most enthusiasts probably prefer to dig into the BIOS and play around with settings there like Curve Optimizer on Ryzen, which lets users set various frequency-voltage scaling values. These are essentially called P-States. If you are not familiar with them, Processor Power Management is done through Advanced Configuration and Power Interface (ACPI) P-states and C-states. While P-states or performance pwoer states handle CPU voltage-frequency scaling, C-states deal with CPU sleep states so that some of the CPU functions, which are not necessary at that moment, can be disabled. The P-states and C-states work together to make the processor run more efficiently. It helps the OS and apps determine which cores can be parked and which should be boosted. Of course not every user is an enthusiast or knows the technicalities and integrities of how things like overclocking or undervolting work. Thankfully for them Windows itself offers something pretty cool, though it is hidden by default on all systems. By default, Windows only has two P-States, "Minimum Processor State" and "Maximum Processor State." However, this can be changed with a Registry trick to expand the options under a secret "Processor performance boost mode" dropdown. This essentially enables the HWP or hardware P-States available on a device, and these are not controlled just by the OS itself as the underlying hardware gets involved too. In total there are five Processor Performance Boost Mode profiles that control how Windows requests and allows CPU turbo/boost behavior under the different power policies. They are: Disabled: In this mode, processor boosting is effectively turned off. The CPU will avoid entering turbo or boost frequencies and instead operate closer to its base frequency ceiling. This can significantly reduce power consumption and heat output, but at the cost of reduced burst performance and responsiveness in short workloads. Enabled: This is the standard behavior where boost functionality is allowed under normal conditions. The processor can opportunistically increase frequency when workload demands it, balancing performance gains with power and thermal constraints as managed by the system. Aggressive: Aggressive mode favors performance more heavily, allowing the CPU to enter higher boost states more readily and sustain them longer. This should in theory improve responsiveness under bursty or heavy workloads but increases power draw and thermal output compared to the default enabled behavior. Efficient Enabled: This mode still allows boosting, but with a stronger bias toward energy efficiency. The system attempts to use boost more selectively, avoiding unnecessary frequency spikes when the performance gain is marginal. Efficient Aggressive: This is a hybrid approach where boost is still performance-responsive, but the system continuously weighs efficiency more heavily than in Aggressive mode. It aims to deliver noticeable performance improvements while reducing wasted power in less demanding scenarios. Here's how to enable the Processor performance boost mode: Open Registry Editor: Press Win+R, type regedit, and click OK. Go to: HKLM\SYSTEM\CurrentControlSet\Control\Power\PowerSettings\54533251-82be-4824-96c1-47b60b740d00\be337238-0d82-4146-a960-4f3749d470c7 (where HKLM stands for HKEY_LOCAL_MACHINE_) Modify the value of Attributes from 1 to 2 (you can find modify option by right-clicking) After that, exit Registry, you should now be able to see the new "Processor performance boost mode" dropdown menu: As you can see there are now five new P-States or CPPC states or power profile available that help define the boost mode processor setting on your PC. Wrapping it up here's a quick run-down of the settings as defined by Microsoft itself. Setting Description Disabled The corresponding P-state-based behaviour is disabled. Collaborative Processor Performance Control (CPPC) behaviour is disabled. Enabled The corresponding P-state-based behaviour is enabled. CPPC behaviour is Efficient Enabled. Aggressive The corresponding P-state-based behaviour is enabled. CPPC behaviour is Aggressive. Efficient Enabled The corresponding P-state-based behaviour is Efficient. CPPC behaviour is Efficient Enabled. Efficient Aggressive The corresponding P-state-based behaviour is Efficient. CPPC behaviour is Aggressive. Aggressive At Guaranteed Windows calculates the desired extra performance above the guaranteed performance level, and asks the processor to deliver that specific performance level. Efficient Aggressive At Guaranteed Windows always asks the processor to deliver the highest possible performance above the guaranteed performance level. In the next part we shall be comparing these settings to explore how much of a benefit or regression they can provide in terms of performance and power efficiency. If you decide to change the values on your system and are experiencing problems like crashes or an overheating PC, make sure to revert the steps back to the original state.
    • I think he means you haven't reviewed previous UFC games. Of course it doesn't matter... Every time you just report on something that involves the President even if just simply what happened you guys usually get accused of being anti-Trump. We live in fun times.
    • So how did you solve the problem? Disabling Secure Boot isn’t a solution.
  • Recent Achievements

    • One Month Later
      Leroy Jethro Gibbs earned a badge
      One Month Later
    • Conversation Starter
      flexorcist earned a badge
      Conversation Starter
    • One Month Later
      AndreaB earned a badge
      One Month Later
    • One Month Later
      agatameier earned a badge
      One Month Later
    • Week One Done
      agatameier earned a badge
      Week One Done
  • Popular Contributors

    1. 1
      +primortal
      518
    2. 2
      +Edouard
      198
    3. 3
      PsYcHoKiLLa
      147
    4. 4
      ATLien_0
      95
    5. 5
      Steven P.
      77
  • Tell a friend

    Love Neowin? Tell a friend!