Re: [Lse-tech] Re: 10.31 second kernel compile

Andi Kleen
2002-03-16T19:32:50Z

yodaiken@fsmlabs.com writes:

> is there a 64 bit machine with hardware search of pagetables? Even ibm
> only has a hardware search of hash tables - which we agree are simply
> a means of making your hardware TLB larger and slower.

x86-64 aka AMD Hammer does hardware (or more likely microcode) search of
page tables.
It has a 4 level page table with 4K pages. Generic Linux MM code only sees
the first slot in 4th level page limit user space to 512GB with 3 levels.
Direct mappings and kernel mappings are handled specially by architecture
specific code outside that first slot.

The CPU itself has I/D TLBs split into L1 and L2.

-Andi