Re: Interruptible sleeps (was Re: CommitFest 2009-07: Yay, Kevin! Thanks, reviewers!)

On 06/09/10 23:10, Markus Wanner wrote:
> Good. How about syscall overhead? One more write operation to the
> self-pipe per signal from within the signal handler and one read to
> actually clear the 'ready' state of the pipe from the waiter portion of
> the code, right?

Right.

> Do we plan to replace all (or most) existing internal signals with these
> latches to circumvent the interruption problem? Or just the ones we need
> to wait for using pg_usleep()?

At least the poll loops in bgwriter and walwriter need to be replaced if
we want to fix the issue Tom mentioned earlier that the server currently
wakes up periodically, waking up the CPU which wastes electricity.
There's no hurry to replace other code.

> For Postgres-R, I'd probably have to extend it to call select() not only
> on the self-pipe, but on at least one other socket as well (to talk to
> the GCS). As long as that's possible, it looks like a more portable
> replacement for the pselect() variant that's currently in place there.

Yeah, that would be a straightforward extension.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com