On 11/10/2014 01:32 PM, Andres Freund wrote:
During benchmarking/debugging I just had the problem that autovacuum was signalled at an insane rate - leading to more than one hundred autovac workers being started per second. Leading to a overall slowdown of more than 90% and the anti-wraparound vacuum not finishing.
Ouch.
The problem is that I couldn't easily figure out where all the SIGUSR2's to the autovacuum launcher where coming from. This isn't the first time that I had that kind of problem. Posix provides information about the source of the signal when using SA_SIGINFO style handlers via si_code/si_pid. That information has been available for a *long* while (c.f. http://pubs.opengroup.org/onlinepubs/7908799/xsh/signal.h.html). I've now hacked up my development instance to log something like "autovacuum: invoked by pid 18175". I personally find that quite helpful. I can also imagine it being rather helpful to log information about the sender of SIGINT/TERM interrupts. The existing abstractions make are nearly sufficient to make it easy to optionally use SA_SIGINFO style handlers. Just by redifining SIGNAL_ARGS and pqsigfunc. There unfortunately is two things making it harder: SIG_IGN and SIG_DFL - those unfortunately can't be specified for SA_SIGINFO style handlers (as they have a different signature). So we'd need to use a different function for those two. Comments, ideas?
How about logging a line in the sender of the signal instead? - Heikki -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
