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Date: Mon, 10 Nov 2008 08:02:34 +0000
From: Jamie Lokier <jamie@shareable.org>
Subject: Re: [Qemu-devel] [PATCH,
	v2] Rewrite mmap_find_vma() to work fine on 64-bit hosts with 32-bit
	targets
Message-ID: <20081110080234.GA18267@shareable.org>
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To: andrzej zaborowski <balrogg@gmail.com>
Cc: qemu-devel@nongnu.org

andrzej zaborowski wrote:
> Hi,
> 
> 2008/11/1 Kirill A. Shutemov <kirill@shutemov.name>:
> > On Sat, Nov 01, 2008 at 04:51:10PM +0000, Jamie Lokier wrote:
> >> Kirill A. Shutemov wrote:
> >> > +        /* Unmap and try again with new page */
> >> > +        munmap(ptr, size);
> >> >          addr += qemu_host_page_size;
> >>
> >> Won't this be rather slow if it has to skip a large mapped area, one
> >> page at a time?
> >
> > If we skip more than one page we increase memory fragmentation.
> 
> This approach makes sense, however the iterating over all pages may
> indeed have performance consequences, plus it would be great if people
> who better know linux-user/ than me commented.  I'll assume that
> everyone is happy with this otherwise.

Just briefly to mention that binary search using shorter
probe-mappings can eliminate the page-by-page iteration in this case,
but alas I don't have time in this email to explain how :-)

-- Jamie