Messages in this thread | | | Date | Sat, 20 Nov 2004 12:07:51 +1100 | From | Nick Piggin <> | Subject | Re: page fault scalability patch V11 [0/7]: overview |
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Linus Torvalds wrote: > > On Fri, 19 Nov 2004, Christoph Lameter wrote: > >>Note that I have posted two other approaches of dealing with the rss problem: > > > 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. >
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).
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. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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