A command line based tool I use suddenly stopped working recently. I tried everything before finally compiling it on another OSX box, running it there successfully, and then running ktrace on both to see the differences. One ktrace stopped after an execv, the other kept going, with the next call referencing /var/vm/app_profile.
Some googling revealed (indirectly through arstechnica):
http://developer.apple.com/technotes/tn2002/tn2053.html
in particular:
"In order to reduce application launch times, the kernel now maintains information about the working set of an application between launches (in "/var/vm/app_profile"). Pre-heat files are meant to be transparent to the user; however, developers who are constantly re-working their applications may find that their pre-heat files are getting large. The files may become clogged with out-of-date profiles on applications who's versions have changed. As a result, developers may find that it is good to clear out the old pre-heat files on test machines once in a while. To do this, become super-user and do a rm -r /private/var/vm/app_profile and then reboot. app_profile is the directory which contains the profile files. The directory is automatically re-created on reboot."
And suddenly qmail runs again.
I'm thinking periodic cleaning of /var/vm/app_profile may be in order. Maybe make it part of any reboot sequence.
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