Re: mmap and MAP_FIXED

[Michael <macallan%netbsd.org@localhost>]

Hello,

On Thu, 12 May 2016 17:43:59 +0200
Johnny Billquist <bqt%update.uu.se@localhost> wrote:

> Uh, my point was that the mmap call is only requesting a 4K-sized map, 
> which I wonder what could be the effect on a machine with a larger page 
> size, and an anonymous mapping with a fixed address.

Yeah, I misread the code snippet due to ENOTENOUGHCOFFEE...

> > Also, why MMAP_FIXED in the first place?
> 
> That is a different question, but a very good one. In general, I think 
> it's a bad idea to try and force the address.

I don't see a reason to do it at all - the pointer to it will sit in a
variable anyway, so what does it matter where in the address space it
is? Maybe they're trying to force the start to be aligned to something
bigger than PAGE_SIZE?

have fun
Michael