Need help in creating 8GB RAMDISK

Need help in creating 8GB RAMDISK

[Fawad Lateef]

Hello

I am creating a RAMDISK of 7GB (from 1GB to 8GB). I
reserved the RAM by changing the code in
arch/i386/mm/init.c .......... 

But I am not able to access the RAM from 1GB to 8GB in
a kernel module ........ after crossing the 4GB RAM,
the system goes into standby state. But if I insert
the same module 2 times means one for 1GB to 4GB and
other for 4GB to 8GB. and mount them seprately both
works fine ............ 

Can any one tell me the reason behind this ??? I think
that in a single module we can't access more than 4GB
RAM ...... If this is the reason then what to do ??? I
need 7GB RAMDISK as a single drive ....

Thanks and Regards,

Fawad Lateef


		
__________________________________
Do you Yahoo!?
Yahoo! Mail - You care about security. So do we.
http://promotions.yahoo.com/new_mail

Re: Need help in creating 8GB RAMDISK

[Jeff Garzik]

Fawad Lateef wrote:
> Hello
> 
> I am creating a RAMDISK of 7GB (from 1GB to 8GB). I
> reserved the RAM by changing the code in
> arch/i386/mm/init.c .......... 

On i386 I'm not surprised this ties at 4G.  It's probably too much 
trouble to make part of the ramdisk highmem, and part not.


> Can any one tell me the reason behind this ??? I think
> that in a single module we can't access more than 4GB
> RAM ...... If this is the reason then what to do ??? I
> need 7GB RAMDISK as a single drive ....

Just use ramfs.  Then you don't waste the overhead of putting a 
filesystem on top of the ramdisk.

	Jeff

Re: Need help in creating 8GB RAMDISK

[William Lee Irwin III]

On Sun, Jul 04, 2004 at 02:25:23AM -0700, Fawad Lateef wrote:
> I am creating a RAMDISK of 7GB (from 1GB to 8GB). I
> reserved the RAM by changing the code in
> arch/i386/mm/init.c .......... 
> But I am not able to access the RAM from 1GB to 8GB in
> a kernel module ........ after crossing the 4GB RAM,
> the system goes into standby state. But if I insert
> the same module 2 times means one for 1GB to 4GB and
> other for 4GB to 8GB. and mount them seprately both
> works fine ............ 
> Can any one tell me the reason behind this ??? I think
> that in a single module we can't access more than 4GB
> RAM ...... If this is the reason then what to do ??? I
> need 7GB RAMDISK as a single drive ....

The state of affairs here is too sad to describe. You are going to
have to find some other way to do what you're trying to do.


-- wli

Re: Need help in creating 8GB RAMDISK

[Joel Jaeggli]

On Sun, 4 Jul 2004, Fawad Lateef wrote:

> Hello
> 
> I am creating a RAMDISK of 7GB (from 1GB to 8GB). I
> reserved the RAM by changing the code in
> arch/i386/mm/init.c .......... 
> 
> But I am not able to access the RAM from 1GB to 8GB in
> a kernel module ........ after crossing the 4GB RAM,
> the system goes into standby state. But if I insert
> the same module 2 times means one for 1GB to 4GB and
> other for 4GB to 8GB. and mount them seprately both
> works fine ............ 

on a non-64bit intel architecture you can only grab 4GB of ram per 
process because that's how big the page table is. There are 16 4GB page 
tables for the 64GB ram that intel machines are capable of addressing.
 
> Can any one tell me the reason behind this ??? I think
> that in a single module we can't access more than 4GB
> RAM ...... If this is the reason then what to do ??? I
> need 7GB RAMDISK as a single drive ....
> 
> Thanks and Regards,
> 
> Fawad Lateef
> 
> 
> 		
> __________________________________
> Do you Yahoo!?
> Yahoo! Mail - You care about security. So do we.
> http://promotions.yahoo.com/new_mail
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
> 

-- 
-------------------------------------------------------------------------- 
Joel Jaeggli  	       Unix Consulting 	       joelja@darkwing.uoregon.edu    
GPG Key Fingerprint:     5C6E 0104 BAF0 40B0 5BD3 C38B F000 35AB B67F 56B2

Re: Need help in creating 8GB RAMDISK

[Eric W. Biederman]

Fawad Lateef <fawad_lateef@yahoo.com> writes:

> Hello
> 
> I am creating a RAMDISK of 7GB (from 1GB to 8GB). I
> reserved the RAM by changing the code in
> arch/i386/mm/init.c .......... 
> 
> But I am not able to access the RAM from 1GB to 8GB in
> a kernel module ........ after crossing the 4GB RAM,
> the system goes into standby state. But if I insert
> the same module 2 times means one for 1GB to 4GB and
> other for 4GB to 8GB. and mount them seprately both
> works fine ............ 
> 
> Can any one tell me the reason behind this ??? I think
> that in a single module we can't access more than 4GB
> RAM ...... If this is the reason then what to do ??? I
> need 7GB RAMDISK as a single drive ....

What do you need this for?

Mostly it looks like you just need to use kmap, but...
As other have pointed out ramfs is usually the better solution,
and you don't need to code anything.

Or are you trying to use an 7GB initrd.  An interesting idea
but that would take a little bootloader hacking to make work.

Eric

Re: Re: Need help in creating 8GB RAMDISK

[Fawad Lateef]

> ebiederm@xmission.com (Eric W. Biederman) writes:
> 
> What do you need this for?
> 
> Mostly it looks like you just need to use kmap,
> but...
> As other have pointed out ramfs is usually the
> better solution,
> and you don't need to code anything.
> 
> Or are you trying to use an 7GB initrd.  An
> interesting idea
> but that would take a little bootloader hacking to
> make work.

Actually I need 7GB RAMDISK to use with my Caching
Drive Project. I have to use RAMDISK of 7GB or more
for the Caching purpose. The Architecture is like Disk
Caching Disk (DCD), but here I hav to use RAMDISK. 

I created RAMDISK using physical address as I hav
reserved all RAM above 1GB for my RAMDISK, but I am
not able to create RAMDISK of 7GB as a single Drive. 

Is there any Idea regarding this ????

Fawad Lateef



		
__________________________________
Do you Yahoo!?
Yahoo! Mail - 50x more storage than other providers!
http://promotions.yahoo.com/new_mail

Re: Need help in creating 8GB RAMDISK

[John Richard Moser]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1



Fawad Lateef wrote:
|>ebiederm@xmission.com (Eric W. Biederman) writes:

| Actually I need 7GB RAMDISK to use with my Caching
| Drive Project. I have to use RAMDISK of 7GB or more
| for the Caching purpose. The Architecture is like Disk
| Caching Disk (DCD), but here I hav to use RAMDISK.

What does this project do?

|
| I created RAMDISK using physical address as I hav
| reserved all RAM above 1GB for my RAMDISK, but I am
| not able to create RAMDISK of 7GB as a single Drive.
|
| Is there any Idea regarding this ????
|
| Fawad Lateef
|
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.4 (GNU/Linux)
Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org

iD8DBQFA8GLwhDd4aOud5P8RAl4AAJ4u4G6oSp8QSfWOrRsvCUtyPRA4mgCfc/jP
f11sCX/hVbpU28p7zCF1E2g=
=FR6S
-----END PGP SIGNATURE-----

Re: Need help in creating 8GB RAMDISK

[Junio C Hamano]

If I understand correctly, earlier you said that you can use
your RAM into multiple ramdisks totalling 7GB or more, and the
only thing you are unable to do is to make it a single ramdisk.
If that is the case, I guess you should be able to kludge those
ramdisks together using raid0 or LVM.