[Users] RE: Trouble getting the 4G (a.k.a. hugemem) patch to work.

[Bailey, Darragh]

I'm guessing that you are using the 32bit version since 64bit version doesn't require a hugemem version to address about 4GB.

You should try using the PAE version, see the following post
http://www.mail-archive.com/rhelv5-list@redhat.com/msg04272.html

It explains that if you use the standard 32bit hugemem version that much of the memory area reserved for the kernel is used up for addressing the memory above 4GB. Where as the PAE kernel is for systems that support PAE, which has 36bits for addressing memory and will avoid any weird memory mapping issues all the way up to 64GB. Still though if you need a system with more than 16GB, you're better off using 64bit.

--
Regards,
Darragh Bailey

Systems Software Engineer
Hewlett Packard Galway Ltd.

Postal Address:    Hewlett Packard Galway Limited, Ballybrit Business Park, Galway 
Registered Office: Hewlett Packard Galway Limited, 63-74 Sir John Rogerson's Quay Dublin 2
Registered Number: 361933

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> -----Original Message-----
> From: users-bounces at openvz.org 
> [mailto:users-bounces at openvz.org] On Behalf Of Edward Hibbert
> Sent: 09 April 2009 13:30
> To: users at openvz.org
> Subject: [Users] RE: Trouble getting the 4G (a.k.a. hugemem) 
> patch to work.
> 
> One other bit of info; I'm fairly sure that the 4G patch is 
> built in to the kernel, because I can see this during the 
> boot sequence:
>  
> mapped 4G/4G trampoline to fff6d000.
> 
> So that leaves me baffled as to why I can't get a process above 3G.
> 
> ________________________________
> 
> From: Edward Hibbert 
> Sent: 09 April 2009 11:41
> To: 'users at openvz.org'
> Subject: Trouble getting the 4G (a.k.a. hugemem) patch to work.
> 
> 
> Apologies if this is a dumb FAQ.  
>  
> I'm trying to get a kernel with what's known in the RedHat 
> world as hugemem, i.e. 4G user space.  I've downloaded a -ent 
> version of the 2.6.18 kernel, and also tried building one 
> myself, but neither of these seems to allow me to exceed 3G.  
>  
> The source code does seem to have 4G macros in it, and I find 
> it hard to believe that the patch simply doesn't work - so 
> I'm more inclined to think I'm doing something stupid.  
>  
> Any suggestions?  Yes, yes, I know we should move to 64-bit, 
> but that's not an option right now.
>  
> Regards,
>  
> Edward.
>