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


On Dec 12 14:19, Christopher Faylor wrote:
> On Wed, Dec 12, 2012 at 06:27:33PM +0100, Corinna Vinschen wrote:
> >On Dec 12 18:15, Corinna Vinschen wrote:
> >> On Dec 12 12:11, Christopher Faylor wrote:
> >> > 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.
> >> 
> >> Which would speak for adding a "nosparse" mount option.
> >
> >...or not.  The problem is not to add the mount option, but to make sure
> >people know that option and use it when "cygwin is slow".  This rather
> >speaks for making nosparse the default and "sparse" the option, I guess.
> 
> Actually, if the assertions here are correct then wouldn't mounting /bin
> as "cygexec" also make things better?

No.  /bin isn't the problem.  Running self-built executables is.  If you
have a build system which runs self-built executables as part of the
build process (xgcc), you'd end up with a very slow build, apparently.

Idle musing:  It would be interesting to know if building and testing a
gcc toolchain would run much faster if we disable the automatic
spare-file creation in lseek/write.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat


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