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Re: can a 32 bit process use more than 2GB?



Hi,

are you sure? you can address 4G but for the design of the kernel you only
have 2GB

http://kerneltrap.org/node/2450
http://web.archive.org/web/20080424081633/lwn.net/Articles/75174/

<http://web.archive.org/web/20080424081633/lwn.net/Articles/75174/>thanks,

ESG

2010/3/17 Nigel Wade <nmw ion le ac uk>

> ESGLinux wrote:
> > Hi,
> >
> > I´m reading a post about the memory use for a java application:
> >
> http://web.archive.org/web/20080313075240/http://goobsoft.homeip.net/Wiki.jsp?page=JavaDebianTuning
> >
> > and there is a thing that surprise me:
> > Read this  and to the point where you understand that a 32-process on
> Linux
> > only has 2GB of addressible space. In fact, back in 1999, Linus decreed
> that
> > 32-bit Linux would never, ever support more than 2GB of memory. "This is
> not
> > negotiable."
> >
> > So I have a machine running RHEL x64 but  I have a process that run over
> > only 32 bit (the JVM), Reading this I think my process only can use 2Gb
> of
> > memory.
> >
> > is it true? is it  oficial documented anywhere?
> >
> > Thanks in advance,
> >
> > ESG
>
>
> No, the 32bit address space limit is 4GB, not 2GB.
>
> $ java -Xmx3500m -version
> java version "1.6.0_15"
> Java(TM) SE Runtime Environment (build 1.6.0_15-b03)
> Java HotSpot(TM) Server VM (build 14.1-b02, mixed mode)
>
> $ java -Xmx4500m -version
> Invalid maximum heap size: -Xmx4500m
> The specified size exceeds the maximum representable size.
> Could not create the Java virtual machine.
>
> If you want more address space than this use a 64bit JVM.
> Using a 64bit JVM then:
>
> $ java -Xmx4500m -version
> java version "1.6.0_17"
> Java(TM) SE Runtime Environment (build 1.6.0_17-b04)
> Java HotSpot(TM) 64-Bit Server VM (build 14.3-b01, mixed mode)
>
> --
> Nigel Wade, System Administrator, Space Plasma Physics Group,
>            University of Leicester, Leicester, LE1 7RH, UK
> E-mail :    nmw ion le ac uk
> Phone :     +44 (0)116 2523548, Fax : +44 (0)116 2523555
>
> --
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