Re: postgresql and process titles

On Tue, Jun 13, 2006 at 10:36:27PM -0400, Tom Lane wrote:
> * not clear whether the interrupt happens when waiting for I/O.  I
> already mentioned that this would be a problem for EXPLAIN ANALYZE,
> but it might be no big deal for the other uses.

If we're going y UNIX signal semantics, in theory any interruptable
function (as listed on the signal manpage) would be interrupted every N
milliseconds to handle the interrupt. So yes, if possible the interrupt
will be serviced anyway, even during I/O, by aborting a restarting the
I/O continuously. Not terribly efficient.

With one big exception: sometimes I/O is non-interruptable (the good
old D state). In this case the interrupts will happen but will simply
be queued and in fact will all be dropped except the last one
(non-realtime signals are never stacked). The handler will probably be
called the moment it returns to user-space.

Note: Do we want SIGPROF, SIGALRM or SIGVTALRM? There's apparently a
distinction, see: http://en.wikipedia.org/wiki/SIGPROF

Have a nice day,
--
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.