Re: Removal of unexec support from glibc malloc

[Ken Raeburn]

> The attached patch brings down the temacs load time to under 0.5 seconds.

Excellent, I was pretty sure it should still be possible; I’d gotten to around 
there before.

Still not good enough, IMNSHO, but all we have to do now is shave another half 
second off…. :-)

> 
> The major offender is find_string_data_in_pure in src/alloc.c, and
> setting purify to nil gets rid of that.  Some additional savings come
> from removing the after-load-function hook in loadup.el, as you
> suggested, but they are comparatively minor.

Thinking back some more on my experiments last year, I guess I’m not surprised. 
I wish I’d made more notes. I think I started with configuring CANNOT_DUMP 
(which would disable the purify code) and profiled it, and the first obvious 
time sink to tackle was the excessive mutex calls (a Mac specific issue, AFAIK, 
though it’s possible glibc/Linux and others could benefit a little); after 
that, tweaking the GC helped me push the startup time down a little bit 
further, but it was a smaller issue.

Ken