6:11 a.m.
I just saw the announcement of a new Fedora kernel with this change note:
A large change over previous kernels has been made. The 4G:4G memory
split patch has been dropped, and Fedora kernels now revert back to
the upstream 3G:1G kernel/userspace split.
A bit of googling indicates that the 4G:4G patch is needed for systems with
a lot of RAM (eg. 32 GB or more) because the kernel memory tables scale
with the size of physical memory and a 32 GB system uses 0.5 GB for the
table, half the kernel space available to a 3G:1G system. A 64 GB system
won't boot because all of kernel memory is needed for the table.
<http://www.uwsg.iu.edu/hypermail/linux/kernel/0307.1/0246.html>
Was this reversion done for performance or for some other reason? I'd guess
most consumer systems won't need 4G:4G as they won't have anything like
that much memory, and it only makes sense for an enterprise class server.
6:24 a.m.
On Tue, 2005-01-04 at 04:11 -0800, Kenneth Porter wrote:
I just saw the announcement of a new Fedora kernel with this change
note:
> A large change over previous kernels has been made. The 4G:4G memory
> split patch has been dropped, and Fedora kernels now revert back to
> the upstream 3G:1G kernel/userspace split.
A bit of googling indicates that the 4G:4G patch is needed for systems with
a lot of RAM (eg. 32 GB or more)
and for people with less ram but who want to run java with lots of
threads... in that case you care a lot about the extra 1Gb of userspace
address space. Even with a moderate amount of threads this makes the
java garbage collector run less frequently -> nicer performance ;)
8:01 p.m.
Am Dienstag, den 04.01.2005, 13:24 +0100 schrieb Arjan van de Ven:
On Tue, 2005-01-04 at 04:11 -0800, Kenneth Porter wrote:
> A bit of googling indicates that the 4G:4G patch is needed for systems with
> a lot of RAM (eg. 32 GB or more)
and for people with less ram but who want to run java with lots of
threads... in that case you care a lot about the extra 1Gb of userspace
address space. Even with a moderate amount of threads this makes the
java garbage collector run less frequently -> nicer performance ;)
Well, remains the question, why the 4G:4G patch has been dropped now.
Would be quite interesting to know (after all the pain that patch caused
in some circumstances but which are mostly resolved now)
Peter
6:36 a.m.
On 4 Jan 2005, at 13:11, Kenneth Porter wrote:
I just saw the announcement of a new Fedora kernel with this change
note:
> A large change over previous kernels has been made. The 4G:4G memory
> split patch has been dropped, and Fedora kernels now revert back to
> the upstream 3G:1G kernel/userspace split.
A bit of googling indicates that the 4G:4G patch is needed for systems
with a lot of RAM (eg. 32 GB or more) because the kernel memory tables
scale with the size of physical memory and a 32 GB system uses 0.5 GB
for the table, half the kernel space available to a 3G:1G system. A 64
GB system won't boot because all of kernel memory is needed for the
table.
<http://www.uwsg.iu.edu/hypermail/linux/kernel/0307.1/0246.html>
Was this reversion done for performance or for some other reason? I'd
guess most consumer systems won't need 4G:4G as they won't have
anything like that much memory, and it only makes sense for an
enterprise class server.
Maybe the 4-level Pagetable changes Andrea Arcangeli introduced into
2.6.10 are related?
7:30 a.m.
On Tue, 4 Jan 2005, Felipe Alfaro Solana wrote:
Maybe the 4-level Pagetable changes Andrea Arcangeli introduced into
2.6.10 are related?
Not really, Andi Kleen's 4-level page tables are mostly
relevant on x86-64, where they can be used to have more
than 512MB of virtual memory per process.
--
"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it." - Brian W. Kernighan
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participants (5)
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Arjan van de Ven -
Felipe Alfaro Solana -
Kenneth Porter -
Peter Boy -
Rik van Riel