Re: Performance monitor signal handler

Jan Wieck <JanWieck(at)yahoo(dot)com> writes:
> Just to get some evidence at hand - could some owners of
> different platforms compile and run the attached little C
> source please?
> (The program tests how much data can be stuffed into a pipe
> or a Sys-V message queue before the writer would block or get
> an EAGAIN error).

One final followup on this --- I wasted a fair amount of time just
now trying to figure out why Perl 5.6.0 was silently hanging up
in its self-tests (at op/taint, which seems pretty unrelated...).

The upshot: Jan's test program had left a 16k SysV message queue
hanging about, and that queue was filling all available SysV message
space on my machine. Seems Perl tries to test message-queue sending,
and it was patiently waiting for some message space to come free.

In short, the SysV message queue limits are so tiny that not only
are you quite likely to get bollixed up if you use messages, but
you're likely to bollix anything else that's using message queues too.

regards, tom lane