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From: Eric Dumazet (dada1@cosmosbay.com)
Date: Wed Dec 15 2004 - 02:41:25 EST


Andi Kleen wrote:

>
> I actually considered implementing it for x86-64 some time ago
> for the modules, but then I never bothered. On AMD systems
> I actually prefer to use small pages here. The reason is that
> Opteron has a separated large and small pages TLB and the small
> pages TLB is much bigger. When someone else uses huge TLB
> pages too (user space or kernel direct mapping) then it's actually
> a good idea to use small pages.

Interesting...

I actually use dual Opterons systems, with very large route cache hashes
and tcp hashes. (rhash_entries=524288 thash_entries=524288), and a
Hugetlb aware user space programs.

x86info tells me (maybe wrongly)

Family: 15 Model: 5 Stepping: 8
CPU Model : Opteron
Instruction TLB: Fully associative. 32 entries.
Data TLB: Fully associative. 32 entries.

and /proc/cpuinfo tells me :
model name : AMD Opteron(tm) Processor 248
TLB size : 1088 4K pages

My questions are :

1) Are the route cache and tcp hashes use big pages (2MB) on 2.6.5/2.6.9
x86_64 kernels.
2) What are the exact number of data TLB entries (for small pages and
huge ones) for opterons ?
3) All networks interrupts are handled by CPU0. Should we really use
NUMA interleaved memory for hashes in this case ?

Thank you
Eric Dumazet
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