Re: Performance monitor signal handler

Jan Wieck <JanWieck@Yahoo.com> writes:
>     Uh - not much time to spend if the statistics should at least
>     be  half  accurate. And it would become worse in SMP systems.
>     So that was a nifty idea, but I think it'd  cause  much  more
>     statistic losses than I assumed at first.

>     Back to drawing board. Maybe a SYS-V message queue can serve?

That would be the same as a pipe: backends would block if the collector
stopped accepting data.  I do like the "auto discard" aspect of this
UDP-socket approach.

I think Philip had the right idea: each backend should send totals,
not deltas, in its messages.  Then, it doesn't matter (much) if the
collector loses some messages --- that just means that sometimes it
has a slightly out-of-date idea about how much work some backends have
done.  It should be easy to design the software so that that just makes
a small, transient error in the currently displayed statistics.
        regards, tom lane