Messages in this thread | | | Date | Fri, 26 Mar 2004 12:33:03 -0800 | From | Andrew Morton <> | Subject | Re: Fw: potential /dev/urandom scalability improvement |
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David Mosberger <davidm@napali.hpl.hp.com> wrote: > > >>>>> On Fri, 26 Mar 2004 10:49:04 -0800, Andrew Morton <akpm@osdl.org> said: > > Andrew> But the start address which is fed into prefetch_range() may > Andrew> not be cacheline-aligned. So if appropriately abused, a > Andrew> prefetch_range() could wander off the end of the user's > Andrew> buffer and into a new page. > > Andrew> I think this gets it right, but I probably screwed something > Andrew> up. > > Please, let's not make this more complicated than it is. The > cacheline alignment doesn't matter at all. Provided prefetch_range() > is given a range of guaranteed to be valid memory, then it will be > fine. It never touches anything outside the specified range.
If someone does, say,
prefetch_range(some_pointer, sizeof(*some_pointer));
then it is possible that prefetch_range() could
a) execute a prefetch at addresses which are not PREFETCH_STRIDE-aligned and, as a consequence,
b) prefetch data from the next page, outside the range of the user's (addr,len).
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