Messages in this thread | | | Date | Thu, 12 Aug 2010 12:08:07 +0200 | From | Micha Nelissen <> | Subject | Re: Why is get_user_pages so slow? |
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Hi Kevin,
Kevin Easton wrote: > Yep, you are. Because your pointer 'p' is a pointer to int, when you > increment it by 0x1000 in your loops you are actually incrementing it by > 0x1000 * sizeof(int) - so you're only actually touching one page in four.
Oops sorry, thanks for catching my mistake.
I also discovered the following: if I read from all pages, then call get_user_pages, it is still quite slow (did I get a read-only page?). However, if I touch all pages by writing to them, then get_user_pages becomes a factor 40 times faster or so.
All is clear now, I think. Thanks.
Micha
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