Re: page fault scalability patch V11 [0/7]: overview

Christoph Lameter
2004-11-20T01:29:06Z

On Sat, 20 Nov 2004, Nick Piggin wrote:

> I think this sounds like it might be a good idea. I prefer it to having
> the unbounded error of sloppy rss (as improbable as it may be in practice).

It may also be faster since the processors can have exclusive cache lines.

This means we need to move rss into the task struct. But how does one get
from mm struct to task struct? current is likely available most of
the time. Is that always the case?

> The per thread rss may wrap (maybe not 64-bit counters), but even so,
> the summation over all threads should still end up being correct I
> think.

Note though that the mmap_sem is no protection. It is a read lock and may
be held by multiple processes while incrementing and decrementing rss.
This is likely reducing the number of collisions significantly but it wont
be a guarantee like locking or atomic ops.