RE: [RFC] 4-level page table directories.

Luck, Tony
2005-11-04T17:58:51Z

>It turns out that we have measurable performance regression with
>4-level page table running industry database benchmark, the penalty
>is ~0.2% (I thought the number would be smaller than 0.2%, but ...).
>Our resolution with this workload is typically 0.05%.

That makes it tough to make 4-level the default. If there were a
lot more users that needed 4-level, I might tell Ken he'd have to
just live with it ... but this is only needed for a few HPC jobs
on very, very high end machines.

I'll put the patches into the test tree as they are (with 4-level
as the default) so that we'll get some test exposure in -mm. But
if they move into the base it will be with 3-level as the default.

-Tony