Re: [Qemu-devel] [PATCH, v2] Rewrite mmap_find_vma() to work fine on 64-bit hosts with 32-bit targets

[Kirill A. Shutemov]

On Fri, Nov 14, 2008 at 01:08:45PM +0000, Jamie Lokier wrote:
> Paul Brook wrote:
> > It's a basic binary search. The problem with it being that as with
> > any other binary search it relies on being able to do "probes".  In
> > this case that involves mapping and unmapping the region, which I'd
> > expect to be fairly high overhead.
> 
> But much less overhead than probing every page address as the current
> linear search does.  The linear algorithm also does a map+unmap in its
> probes.  That's the point.

Overhead is not very big. It takes 0,7 seconds on my Core2 T7200 to make
150000 probes.

Anyway, in most cases mmap_find_vma() need only one probe.

-- 
Regards,  Kirill A. Shutemov
 + Belarus, Minsk
 + ALT Linux Team, http://www.altlinux.org/

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