[CentOS] Is 4GB memory the 64bit switch tipping point?

Akemi Yagi amyagi at gmail.com
Mon Dec 8 12:01:34 UTC 2008


On Sun, Dec 7, 2008 at 11:02 PM, Ignacio Vazquez-Abrams
<ivazqueznet at gmail.com> wrote:
> On Sun, 2008-12-07 at 23:06 -0700, Kenneth Burgener wrote:
>>
>> 1.  4GB Memory.

I'd like to add a note regarding the 4G/4G split issue.  Unlike
hugemem in CentOS/RHEL-4, the PAE kernel in CentOS/RHEL-5 does not
provide 4GB per user process.  In this regard, there is no
hugemem-equivalent in CentOS/RHEL-5.  This was mentioned in the
upstream bugzilla [1].  In other words, applications that can take
advantage of 4GB per process should benefit from the 64-bit.

There is a description in section 40.1 (kernel-PAE) of the CentOS
online documentation:

"4GB/4GB split: 4GB of virtual address space for the kernel and almost
4GB for each user process on x86 systems"

This is incorrect and has been removed from the same page upstream.  I
filed a bug report regarding updating the CentOS lnline doc [2].

[1] https://bugzilla.redhat.com/show_bug.cgi?id=241314
[2] http://bugs.centos.org/view.php?id=3231

Akemi / toracat


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