Understanding Superfetch in Windows 7

[KeeperOfThePizza]

Does anyone know what kind of changes MSFT did to superfetch? and I need alittle help understand how superfetch really works.. I know superfetch caches your well used programs so they start faster.. But at what point does it re-cache? When i install a new program? Could use alittle information.

[ToneKnee]

Does anyone know what kind of changes MSFT did to superfetch? and I need alittle help understand how superfetch really works.. I know superfetch caches your well used programs so they start faster.. But at what point does it re-cache? When i install a new program? Could use alittle information.

I believe the system just learns you habbits a loads the most common files you used into the memory. When a application starts (lets say an application heavy on memory) it releases the memory to the application. When that application terminates, it then re-caches any commonly used data back into memory. I believe the system does everything automatically and doesn't "reset" itself every time an application gets installed.

I hope this helps.

[KeeperOfThePizza]

Thanks!

[soulburner]

Superfetch in Windows 7 is also a lot less aggressive than Vista's. On Vista I was often annoyed that it started caching almost immediately after logging in and just had to fill the entire available memory. (Edit - it also cached large files used by applications, like partial torrent downloads - W7 doesn't)

Windows 7 is a bit different - after logging in, I can see some amount of memory is already used for the cache, but the system waits a few minutes before really starting "superfetching". It also doesn't use all the available memory if there's no need to (not enough data to cache). Also, after quitting a program, refilling the cache doesn't occur immediately. It seems that the I/O priority is also lower.

Edited June 4, 2009 by soulburner

[MagicAndre1981]

superfetch on Win7 is bad. It doesn't use all of my available RAM for caching.

[Martog]

superfetch on Win7 is bad. It doesn't use all of my available RAM for caching.

Which is a bad thing how? I mean if you had lets say, 12GB of ram via triple channel DDR3 on a i7 platform would you really have enough programs to have that filled?

[ToneKnee]

Which is a bad thing how? I mean if you had lets say, 12GB of ram via triple channel DDR3 on a i7 platform would you really have enough programs to have that filled?

Exactly, and if you had a slow hard drive then it would take time to fill that amount of memory up. Free RAM is wasted RAM, but no point in caching RAM with stuff you actually don't need.

[rakeshishere]

superfetch on Win7 is bad. It doesn't use all of my available RAM for caching.

QFT

[HawkMan]

superfetch on Win7 is bad. It doesn't use all of my available RAM for caching.

Superfetch on both Vista and 7 will generally only max out at about 50%.

except with 7 they added a second limit for low ram machines.

[jamesVault]

it also cached large files used by applications, like partial torrent downloads - W7 doesn't

FALSE! Superfetch doesn't fetch the users files but only the binaries exe and DLL libraries.

[DJ-Light]

You can restart superfetch in Vista and W7 if you disable that service, restart, delete the prefetch, re-enable the service and restart. The next time the PC boot superfetch will start to fetch data like new.

[soulburner]

FALSE! Superfetch doesn't fetch the users files but only the binaries exe and DLL libraries.

What was loading these files then, making my hard drive cry for help? It wasn't indexing, because this location has not been added to be indexed. If I recall correctly, it was svchost.exe with Background I/O priority.

edit - this guy seems to be complaining about the same thing: http://jaysonrowe.com/2009/01/05/thoughts-...fetch-in-vista/ - read the paragraphs above and below the second screenshot.

[jamesVault]

What was loading these files then, making my hard drive cry for help?

it's your poorly written antivirus.

[soonerproud]

Does anyone know what kind of changes MSFT did to superfetch? and I need alittle help understand how superfetch really works.. I know superfetch caches your well used programs so they start faster.. But at what point does it re-cache? When i install a new program? Could use alittle information.

They made it a little less agressive at startup so it doesn't get in the way of a usable desktop. Once the system is idle for a few minutes, then superfetch kicks in and does it's magic.

[MagicAndre1981]

Free RAM is wasted RAM, but no point in caching RAM with stuff you actually don't need.

:rolleyes: I know this, but with 2GB of RAM, Vista fills up the cache (1500MB for me) in less then 2 min and now all apps starts fast. On Win7 I have 500MB free, unused and wasted RAM. This is bad, not the way Vista does it. I'm now back with Vista, because of the superfetch bug under Win7.

[ToneKnee]

:rolleyes: I know this, but with 2GB of RAM, Vista fills up the cache (1500MB for me) in less then 2 min and now all apps starts fast. On Win7 I have 500MB free, unused and wasted RAM. This is bad, not the way Vista does it. I'm now back with Vista, because of the superfetch bug under Win7.

It's not a bug, like it's been stated in this thread, Superfetch has been changed to reflect better system performance. The more and more applications you run, the more memory it will use. Don't be silly.

[soulburner]

it's your poorly written antivirus.

I don't use an AV.

I know what I saw and what my disk went through. It cached utorrent downloads, huge Steam's GCF files and stuff like that. It really does stuff like this: http://jaysonrowe.files.wordpress.com/2009/01/superfetch.png

Windows 7's Superfetch is a huge improvement!

edit:

:rolleyes: I know this, but with 2GB of RAM, Vista fills up the cache (1500MB for me) in less then 2 min and now all apps starts fast. On Win7 I have 500MB free, unused and wasted RAM. This is bad, not the way Vista does it. I'm now back with Vista, because of the superfetch bug under Win7.

You do realize that Vista is caching junk (stuff you will probably never know Windows had) just to keep the Superfetch buffer full?

[MagicAndre1981]

sorry, superfetch in Win7 makes Win7 slower, NOT faster!

[ToneKnee]

I don't use an AV.

I know what I saw and what my disk went through. It cached utorrent downloads, huge Steam's GCF files and stuff like that. It really does stuff like this: http://jaysonrowe.files.wordpress.com/2009/01/superfetch.png

Windows 7's Superfetch is a huge improvement!

Exactly, I'd rather have Superfetch cache applications and not every single file I might commonly use.

sorry, superfetch in Win7 makes Win7 slower, NOT faster!

Sorry, but have you given Windows 7 at least a few days to speed up? People complained about Vista and it's very aggressive way of using Superfetch because it cached literally everything. Windows 7 will take a little longer, but after a few reboots/days of using applications, Windows will learn and use Superfetch efficiently. But, if that doesn't work, I'm going to have a guess and say your problem is down to drivers or a bad install.

[MagicAndre1981]

sorry, I'm using the Win7 Rc for a month! And it's not a bad install. :rolleyes:

[soulburner]

Yup, Windows 7's "standby" memory will increase when you launch more and more applications. After a fresh install, Superfetch uses a few hundred megabytes. After I installed and used applications like Adobe Photoshop, MSVC 2008 and others, I found the blue bar in Resource Manager covering the whole graph, leaving 0-50MB's truly free - just like Vista tries to do after the very first boot, only this time it's filled with program data that I actualy used.

And all apps I used start up much faster than on XP, which is a sign Superfetch does work just fine.

[Subject Delta]

What was loading these files then, making my hard drive cry for help? It wasn't indexing, because this location has not been added to be indexed. If I recall correctly, it was svchost.exe with Background I/O priority.

aysonrowe.com/2009/01/05/thoughts-...fetch-in-vista/[/url] - read the paragraphs above and below the second screenshot.

That thing making your hard disk 'cry for help' is called a paging file, inevitably on systems with lower amounts of memory, things will get paged more often, and of course the actual fetching of your data into memory.

I don't use an AV.

I know what I saw and what my disk went through. It cached utorrent downloads, huge Steam's GCF files and stuff like that. It really does stuff like this: http://jaysonrowe.files.wordpress.com/2009/01/superfetch.png

Windows 7's Superfetch is a huge improvement!

That graph only shows what file the process is accessing, accessing data doesn't automatically mean it is loaded into memory. For the purpose of proof, I opened a large file with WinRar and extracted it to another folder to show the same effect.

[Genius]

is that the 7s activity monitor? Very similar to the one on os x ;)

[ToneKnee]

is that the 7s activity monitor? Very similar to the one on os x ;)

That feature has been there since at least Windows XP, but I think they've rearranged some stuff.

[soulburner]

That thing making your hard disk 'cry for help' is called a paging file, inevitably on systems with lower amounts of memory, things will get paged more often, and of course the actual fetching of your data into memory.

I don't think Vista uses the pagefile so intensively after starting up on a 3GB system. Also, when Vista is accessing data from the pagefile, the resource manager will show pagefile.sys under Disk as the file used.

That graph only shows what file the process is accessing, accessing data doesn't automatically mean it is loaded into memory. For the purpose of proof, I opened a large file with WinRar and extracted it to another folder to show the same effect.

Yes, I know, but whenever you see svchost.exe with a Background I/O priority - it's Superfetch.

The Resource Manager under Vista did not use bytes/second units - it used bytes per minute. When I saw "source 2007 materials.gcf" being read there and the "B/min" value was rising and rising and rising, I think it's fair to conclude it's actualy being read from the disk, and it was done so by svchost.exe with background IO - what other purpose of that than "superfetching" it? Oh, and the amount of free memory kept decreasing, so it wasn't just accessing the data, it was reading it into RAM.

Edited June 4, 2009 by soulburner