06-16-2010
The performance impact is highly workload dependent, but on a fairly typical kernel compile,the PAE penalty works out to be around a 1% performance hit on RedHat’s test boxes.Testing with various other workload mixes has given performance
hits ranging from 0% to 10%.
From Redhat's 2.1 Virtual memory white paper. Things may have changed slightly in 2.6, but as such, it will still produce a slight performance hit.
Last edited by mark54g; 06-16-2010 at 10:52 PM..
10 More Discussions You Might Find Interesting
1. UNIX for Dummies Questions & Answers
Has anyone had any experience with this new processor and its compatability with Linux/Unix? How did it preform comared to regular Athlons and P4's?
I also have one other question. I plan on buying a new dell and fiddling left and right with it. Which type of RAM is better, RDRAM or... (3 Replies)
Discussion started by: KyPeN
3 Replies
2. UNIX for Dummies Questions & Answers
I wish to install Red Hat linux 7.1 on a machine with 16mb of EDO Ram. When I enter the instalation process I am told 'You do not have enough memory'. Is there a way to install RHL with only the 16? Or will I have to upgrade and buy some very expensive EDO.
~ Paul (3 Replies)
Discussion started by: KrazyGuyPaul
3 Replies
3. Debian
Hello all
i own p100 16ram laptop , i would like to run linux on it
i need it for gcc compilation and shell scripting , no gui.
what version of linux should i install , i dont mind to install old one .
tnx allot (5 Replies)
Discussion started by: umen
5 Replies
4. Shell Programming and Scripting
Hi Gurus,
Can someone let me know how to find the RAM size,ROM size and Number of processors for a linux server.
Version :Linux 2.4.9-e.57smp
Also what does "e.57smp" stands for?
Thanks in advance gurus.....
cheers. (3 Replies)
Discussion started by: navojit dutta
3 Replies
5. Linux
Hi,
I want to know what is command to know which will tell wheather linux is 32 or 64 bit (5 Replies)
Discussion started by: manoj.solaris
5 Replies
6. Linux
Where can I get a list that maps the each Linux version to corresponding 32/64 bits model?
e.g.
OS -> Model (ILP32, LP64, ...)
RHLE3 -> ?
RHLE4 -> ?
RHLE5 -> ?
...
It would be better if there is such a list that contains most of current UNIX OS versions.
... (1 Reply)
Discussion started by: princelinux
1 Replies
7. Debian
Hi,
How to enable and use ACL's in linux.
Thx,
siva. (2 Replies)
Discussion started by: Sivaswami
2 Replies
8. Red Hat
Hi,
On server 64bit Hw Arch , Linux 5.0(32bit) is installed it is showing only 3gb of ram though physical is 16gb
can u give me idea why? (4 Replies)
Discussion started by: manoj.solaris
4 Replies
9. Red Hat
Friends ,
Would u plz tell me what is the difference between 32-bit Linux o/s and the 64 bit Linux o/s .
Is there any RAM limitation in this two types of o/s .
Waiting for kind reply ... ... (7 Replies)
Discussion started by: shipon_97
7 Replies
10. Cybersecurity
void main() {
long ((long)(&array));
int x;
for (;;)
{
(array) =+ 1023;
printf("%c", array);
}
}
What is wrong with this code to print Linux RAM? (13 Replies)
Discussion started by: Alux
13 Replies
PAE(4) BSD/i386 Kernel Interfaces Manual PAE(4)
NAME
PAE -- Physical Address Extensions
SYNOPSIS
options PAE
DESCRIPTION
The PAE option provides support for the physical address extensions capability of the Intel Pentium Pro and above CPUs, and allows for up to
64 gigabytes of memory to be used in systems capable of supporting it. With the PAE option, memory above 4 gigabytes is simply added to the
general page pool. The system makes no distinction between memory above or below 4 gigabytes, and no specific facility is provided for a
process or the kernel to access more memory than they would otherwise be able to access, through a sliding window or otherwise.
SEE ALSO
smp(4), tuning(7), config(8), bus_dma(9)
HISTORY
The PAE option first appeared in FreeBSD 4.9 and FreeBSD 5.1.
AUTHORS
Jake Burkholder <jake@FreeBSD.org>
BUGS
Since KLD modules are not compiled with the same options headers that the kernel is compiled with, they must not be loaded into a kernel com-
piled with the PAE option.
Many devices or their device drivers are not capable of direct memory access to physical addresses above 4 gigabytes. In order to make use
of direct memory access IO in a system with more than 4 gigabytes of memory when the PAE option is used, these drivers must use a facility
for remapping or substituting physical memory which is not accessible to the device. One such facility is provided by the busdma interface.
Device drivers which do not account for such devices will not work reliably in a system with more than 4 gigabytes of memory when the PAE
option is used, and may cause data corruption. The PAE kernel configuration file includes the PAE option, and explicitly excludes all device
drivers which are known to not work or have not been tested in a system with the PAE option and more than 4 gigabytes of memory.
Many parameters which determine how memory is used in the kernel are based on the amount of physical memory. The formulas used to determine
the values of these parameters for specific memory configurations may not take into account the fact there may be more than 4 gigabytes of
memory, and may not scale well to these memory configurations. In particular, it may be necessary to increase the amount of virtual address
space available to the kernel, or to reduce the amount of a specific resource that is heavily used, in order to avoid running out of virtual
address space. The KVA_PAGES option may be used to increase the kernel virtual address space, and the kern.maxvnodes sysctl(8) may be used
to decrease the number of vnodes allowed, an example of a resource that the kernel is likely to overallocate in large memory configurations.
For optimal performance and stability it may be necessary to consult the tuning(7) manual page, and make adjustments to the parameters docu-
mented there.
BSD
April 8, 2003 BSD