Performance optimization in av::fixup - use buffered IO, not mapped file

[Christopher Faylor]

On Wed, Dec 12, 2012 at 12:06:08PM -0500, Ryan Johnson wrote:
>It's painfully reproducible. It takes nearly two hours for a gcc 
>bootstrap compiler to configure the various bits of the next stage. It's 
>the same for emacs unexec (as OP reported).

I'd like to see a small controlled test case which demonstrates the
problem.  If the claims here are all true then it should be very easy to
demonstrate without resorting to bootstrapping the compiler.

And, given my comment about setup.exe, I suspect that this isn't going
to be as alarming an issue for the normal Cygwin user as it is for
people who, e.g., rebuild their own compilers.  I'll bet setup.exe
doesn't know anything about sparse files so all of the executables
and dll should not be sparse.

Can anyone confirm or deny that?

cgf