Re: Question on the five-level page table support patches

[John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>]

On 04/24/2017 03:03 PM, Andi Kleen wrote:
> In old Linux hint was a search hint, so if there isn't a hole
> at the hinted area it will search starting from there for a hole
> instead of giving up immediately.

Yep, that's what I meant. It used to work like that and it still
works like that on NetBSD, for example. Although it has apparently
been a long time since it changed [1].

> Now it just gives up, which means every user has to implement
> their own search.

Correct. And the resulting code is usually ugly and inefficient [2].

> Yes I ran into the same problem and it's annoying. It broke
> originally when top down mmap was added I believe
> 
> Before the augmented rbtree it was potentially very expensive, but now
> it should be cheap.

I'm not sure whether I understand what that means.

Thanks,
Adrian

> [1] http://lkml.iu.edu/hypermail/linux/kernel/0305.2/0828.html
> [2] https://hg.mozilla.org/mozilla-central/rev/dfaafbaaa291

-- 
 .''`.  John Paul Adrian Glaubitz
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`. `'   Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
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