Re: page table lock patch V15 [0/7]: overview

Christoph Lameter
2005-01-12T23:54:23Z

On Thu, 13 Jan 2005, Nick Piggin wrote:

> Note that this was with my ptl removal patches. I can't see why Christoph's
> would have _any_ extra overhead as they are, but it looks to me like they're
> lacking in atomic ops. So I'd expect something similar for Christoph's when
> they're properly atomic.

Pointer operations and word size operations are atomic. So this is mostly
okay.

The issue arises on architectures that have a large pte size than the
wordsize. This is only on i386 PAE mode and S/390. S/390 falls back to
the page table lock for these operations. PAE mode should do the same and
not use atomic ops if they cannot be made to work in a reasonable manner.