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

[William Lee Irwin III]

On Fri, Nov 19, 2004 at 11:59:03AM -0800, Linus Torvalds wrote:
> You could also make "rss" be a _signed_ integer per-thread.
> When unmapping a page, you decrement one of the threads that shares the mm 
> (doesn't matter which - which is why the per-thread rss may go negative), 
> and when mapping a page you increment it.
> Then, anybody who actually wants a global rss can just iterate over
> threads and add it all up. If you do it under the mmap_sem, it's stable,
> and if you do it outside the mmap_sem it's imprecise but stable in the
> long term (ie errors never _accumulate_, like the non-atomic case will 
> do).
> Does anybody care enough? Maybe, maybe not. It certainly sounds a hell of 
> a lot better than the periodic scan.

Unprivileged triggers for full-tasklist scans are NMI oops material.


-- wli
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