Messages in this thread | | | Date | Sat, 20 Nov 2004 12:45:59 +1100 | From | Nick Piggin <> | Subject | Re: page fault scalability patch V11 [0/7]: overview |
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Christoph Lameter wrote: > 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. >
Yep.
> 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? >
It is available everywhere that mm_struct is, I guess. So yes, I think `current` should be OK.
> >>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. >
Yeah the read lock won't do anything to serialise it. I think what Linus is saying is that we _don't care_ most of the time (because the error will be bounded). But if it happened that we really do care anywhere, then the write lock should be sufficient. - 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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