System Cache

[Guest]

There is about 1250mb of memory in the computer. The system cache size stays
in the range of 50-70mb no matter what I do. Recently, I ran 4(four)
different games _simultaneously_. Saw free memory drop from 1000mb to 75mb
but the cache size remained below 70mb. What can I do to increase the system
cache size and thus use some of the free memory?

 

[Bob I]

Give it up already.

 

[Sharon F]

There is about 1250mb of memory in the computer. The system cache size stays
in the range of 50-70mb no matter what I do. Recently, I ran 4(four)
different games _simultaneously_. Saw free memory drop from 1000mb to 75mb
but the cache size remained below 70mb. What can I do to increase the system
cache size and thus use some of the free memory?

Your system is working correctly. You don't want anything cached unless
it's necessary. Reason: It's faster reading from memory than from the cache
on the drive.

 

[Guest]

System cache is in memory. It is not on the drive.
_________________________________________________

 

[Sharon F]

System cache is in memory. It is not on the drive.

And as I said, this is a good thing. When your system needs to cache to the
hard drive because the RAM is needed for other tasks, it will do so. As it
stands now, your system is running optimally. No need to change anything.

 

[Guest]

You don't understand. After I boot the computer and reach the desktop, there
is about 1000 mb of free memory which is much more than enough to run games.
There is never a shortage of free memory!
_________________________________________________________________

 

[Bob I]

No, IT'S YOU that doesn't understand, you haven't started giving it
anything in particular to do yet.

 

[msenn]

Windows puts an area of the size of about 80% of the RAM on the local
disk. This is the "file system cache". Windows doesn't show you this
file system cache, but you can imagine it as a large file normally on
your Drive C. When you do large file copies to your disk, you can
monitor the increasing of the cache in the task manager. In this moment
the copied files do not stay in the directory where you meant to copy
them. They are in the file system cache. This can last a long time
until the file system cache is emptied an written to the real location.
Microsoft knows that there are problems with the file system cache when
you have machines with much RAM. Maybe when you backup a system and the
file system cache is not empty there can be a loss of data. In large
domain environments, this can cause problems, if the file system cache
is to big. There may be replication problems. To fix the problem some
companies go the way and reduce the memory of domain controllers to
256MB RAM. Because then the file system cache is 80% of 256MB, and the
problems are gone. There is no way to reduce the file system cache
manually (The only way is reducing RAM). You can find registry hacks,
but they dont work.

 

[John John]

I thought that the File System Cache was an area of memory which held
files recently accessed on the hard drive? If the application then
needs to use the same file again or write to it, it is retrieved from or
written to the much faster memory cache instead of the disk. The files
are held or cached until flushed to the disk.

John

 

[Edwin vMierlo]

Windows puts an area of the size of about 80% of the RAM on the local
disk. This is the "file system cache". Windows doesn't show you this
file system cache, but you can imagine it as a large file normally on
your Drive C.

Not really, where did you get that info, as this is not "file system cache"
Please back this up with a technical article

When you do large file copies to your disk, you can
monitor the increasing of the cache in the task manager. In this moment
the copied files do not stay in the directory where you meant to copy
them. They are in the file system cache.

the copy comands WILL LEAVE a copy in the original directory !
Please ensure you do not mix the term copy with the term move.
And NO, this is not a good explanation of file system cache
Please backup your claims with some technical article

This can last a long time
until the file system cache is emptied an written to the real location.
Microsoft knows that there are problems with the file system cache when
you have machines with much RAM.

Please backup your claim with a technical article.

Maybe when you backup a system and the
file system cache is not empty there can be a loss of data. In large
domain environments, this can cause problems, if the file system cache
is to big. There may be replication problems. To fix the problem some
companies go the way and reduce the memory of domain controllers to
256MB RAM. Because then the file system cache is 80% of 256MB, and the
problems are gone. There is no way to reduce the file system cache
manually (The only way is reducing RAM). You can find registry hacks,
but they dont work.

Again, sorry to be repetative... please, PLEASE, back up your stories with
some technical facts.

 

[Edwin vMierlo]

correct John,

this article explains some of the settings:
http://technet2.microsoft.com/Windo...a031-4461-9e72-59197a7507b61033.mspx?mfr=true

I thought that the File System Cache was an area of memory which held
files recently accessed on the hard drive? If the application then
needs to use the same file again or write to it, it is retrieved from or
written to the much faster memory cache instead of the disk. The files
are held or cached until flushed to the disk.

John

 

[Uwe Sieber]

There is no way to reduce the file system cache
manually (The only way is reducing RAM).

You can do this using a switch in the boot.ini,
either /MAXMEM=nnn or /BURNMEMORY=nnn.
Using Cenatek RamDisk up to V1.7 you can use this
excluded RAM as RamDisk and put the pagefile on
it.
http://www.cenatek.com/product_ramdisk.cfm

Putting the pagefile into a ramdisk is nonsense at
first view but if the goal is to limit the file file
cache size then it may be the solution...


Microsoft has agreed that there is a problem with
a too large file cache. Since NT 5.2 (Windows 2003
Server) there is a new API function to set a limit
for the cache size.


Uwe

 

[Manfred Senn]

Yes, there is a cache in the memory too, and I think this works together
with the file cache. I would be glad if anyone from Microsoft would comment
this ...

I thought that the File System Cache was an area of memory which held files
recently accessed on the hard drive? If the application then needs to use
the same file again or write to it, it is retrieved from or written to the
much faster memory cache instead of the disk. The files are held or cached
until flushed to the disk.

John

 

[John John]

I would be glad if you pointed us to an article about this business of
the file cache being on the hard disc. Lets not confuse the pagefile
with the file cache. I only know of one file cache and it is in an area
of the RAM. Please provide further information for the disc file cache,
I would like to find out what this is all about.

John

 

[Manfred Senn]

That is a big problem!?
I know this issues from a Windows 2003 Troubleshooting training, where the
trainer showed the increasing of the file system cache, while copying a
large amount of files, and we discussed the disadvantages of this
problematic.
You can watch the Cache in Task Manager - Performance - Physical Memory -
Systemcache.
You will see that Systemcache wont fill up to more than 80% of the size of
your RAM.

You wont find anything about that problematic in the internet. Microsoft
doesn't want that this is public.

File system cache an pagefile are totally different things.
You can fix the size of the page file, and you can see the file.
Set your page file to zero, and you will see that it has nothing to do with
the Systemcache. Your system will work.

Again: There is no way to see or fix the size of the file system cache, only
by changing RAM.
Again: Registry hacks dont fix this problem for Windows 2003!!! (maybe 2003
R2 does it? Idont know)
That's the hard truth. Don't put too much RAM in your computer if you dont
really need it. It can be contraproductive.

I know a company in germany that radically reduced RAM in domain controllers
(256MB) and servers because of problems with replication and data
synchronization.

I will contact the company and ask them to post details in the internet.

Manfred

 

[Manfred Senn]

Microsoft has agreed that there is a problem with a too large file cache.
Since NT 5.2 (Windows 2003
Server) there is a new API function to set a limit for the cache size.

I don't believe this. What API function? How to use?

Manfred

 

[John John]

I know the difference between the pagefile and the system cache! I
don't dispute that it might be a problem in some circumstances! What I
don't understand is your initial statement: "Windows puts an area of
the size of about 80% of the RAM on the local disk. This is the "file
system cache"." What is this deal about the file system cache being on
a different file on the hard disc? Where does this information come from?

John

 

[Uwe Sieber]

I don't believe this. What API function? How to use?

The name of the function is SetSystemFileCacheSize:
http://msdn.microsoft.com/library/en-us/sysinfo/base/setsystemfilecachesize.asp

In fact is does not limit the amount of RAM used for the file cache, it
just limits its working set. But I think that's good enough to prevent
Windows from swapping out appication's RAM in favor of a large file
cache.


I'm just writing a small tool to use this function - give me some hours...



Uwe

 

[John John]

The name of the function is SetSystemFileCacheSize:
http://msdn.microsoft.com/library/en-us/sysinfo/base/setsystemfilecachesize.asp

In fact is does not limit the amount of RAM used for the file cache, it
just limits its working set. But I think that's good enough to prevent
Windows from swapping out appication's RAM in favor of a large file
cache.


I'm just writing a small tool to use this function - give me some hours...



Uwe

CacheSet v1.0
http://www.microsoft.com/technet/sysinternals/utilities/CacheSet.mspx

John

 

[Manfred Senn]

Hello John,

You can see the maximum size in Task Manager it is about 80% of the RAM.
As far as I know you cannot manipulate the location of the file system
cache.
It always lies on your default windows drive normally C:
And you cannot backup it, only when you use a image of the disk.

Again, it would be nice if anyone from Microsoft would tell us more about
this.

Manfred