Re: Hinted mmap(2) without MAP_FIXED can fail prematurely

[PHO <pho%cielonegro.org@localhost>]

I expected mmap(2) to search for an available region from the entire 
address space starting from the hint, not only half of it.

On 2/17/22 5:32 PM, Johnny Billquist wrote:
> If it would ignore the hint, what's the point of the hint then?
>
>    Johnny
>
> On 2022-02-17 08:23, PHO wrote:
> > I'm not sure if this is a bug or not, but on NetBSD/amd64 9.2, hinted 
> > mmap(2) without MAP_FIXED can fail prematurely with ENOMEM if all the 
> > regions below the given hint address are occupied.
> >
> > The man page for mmap(2) suggests that the hint is just a hint. 
> > Shouldn't mmap(2) also search for available regions above the hint then?
> >
> > Test code:
> > https://gist.github.com/depressed-pho/a629247b48b3e6178e35a14c62e9d44f#file-mmap-with-hint-c 
> >
> >
> > Test result:
> > https://gist.github.com/depressed-pho/a629247b48b3e6178e35a14c62e9d44f#file-gistfile1-txt