Re: x86, ARM, PARISC, PPC, MIPS and Sparc folks please run this

[Jamie Lokier]

Russell King wrote:
> > > Multiple mappings of the same object rarely occur in my experience, so
> > > the resulting performance loss caused by working around the cache and
> > > writebuffer is something we can live with.
> > 
> > Multiple *writable* mappings.   Don't forget about libc et al.
> 
> I mean in the same group of threads with the same struct mm, not the whole
> system.

Larry means that it's perfectly normal for libc to map the same file
more than once: you have the code section and the data section.

I don't know if ARM's ELF is like the x86, but on the x86 the final
partial page of code or read-only data will be mapped twice, as the
latter part of the page can contain writable data.  This avoids
wasting up to a page's worth of bytes in the ELF file.

-- Jamie

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