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Re: Apple's PFE for GCC is now available
Neil Booth wrote:
Finally, if you're wondering how this relates to the PCH branch, it's
being actively discussed. PFE has both pluses and minuses relative to
the current PCH work, and ideally we'll be able to use both in coming
up with superior precompiled header support for FSF GCC.
Where is it being actively discussed? It's a shame this stuff isn't
out in the open; I'd like to know what the plans are as I have (had)
ideas of my own.
"Actively" is perhaps an exaggeration; at this point it's been mostly
in-person conversation. Now that working PFE sources are available
for people to look at and try, it's worthwhile to move to more
specific discussion online.
So nobody feels in the dark, I'll put up my current favorite idea for
target practice :-) ; use the PFE code for allocation to make sure that
everything goes into large mmap-able blobs, use the tree-marking code
to autogen walkers for freezing/thawing if mmap can't go back to the
same place, use PFE code for managing headers and date checking since
it all exists now, and have a big free-for-all argument about what to
call the dump/load switches. 1/2 :-)
One downside of the big mmap is that it doesn't allow for incremental
loading, but incremental would be a useful fallback to keep the
mmap failure case efficient. Our experience so far is that while
a particular system's mmap wins are predictable, different systems
are randomly different in the size and location of areas to use.
Stan