Re: Optimizing away "ReadFile" calls when Make calls stat()

[jik-cygwin at curl dot com]

>  Date: Tue, 13 Feb 2001 11:25:46 -0800
>  From: "Eric M. Monsler" <emonsler@beamreachnetworks.com>
>  
>  I don't understand the change that you are proposing, unless it is to
>  change the API for stat() to include two more flags.

No.

>  Not to mention that you would have also forked GNU Make, or else added a
>  compilation dependency, that would need to get folded back in.

There are already plenty of Cygwin-specific changes in GNU Make.  This
would simply be one more of them.

>  On re-reading your post, it appears that you are not proposing an API
>  change to stat, but rather another call that will set/unset that part of
>  stat()'s behavior in the DLL.

Yes.

>  For everything in the system?  Is your proposed change MT-safe?

It would have to be made MT-safe, obviously.  While I am not
intimately familiar with how to do such a thing in Cygwin DLL code, I
am confident that the more knowledgeable maintainers of the code would
be able to do so easily.

>  I believe that the proposal to cache the results of ReadFile() was
>  intended to suggest that inside stat(), only one ReadFile might be
>  required.  This seems like a good idea, performance enhancing and
>  standards preserving.  I don't know ReadFile, and so don't know if this
>  would be possible.

Yes, it does seem like a good idea, but it doesn't go far enough for
our needs.  This would still result in thousands (or perhaps even tens
of thousands) of unnecessary ReadFile calls in our builds and would
have a significant performance impact.

  jik

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