Re: Synch Rep v5

On Sat, 2009-01-10 at 19:16 +0900, Fujii Masao wrote:

> On Thu, Dec 18, 2008 at 9:55 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> >> 4. sleeping
> >> http://archives.postgresql.org/pgsql-hackers/2008-12/msg00438.php
> >>
> >> I'm looking for the better idea. How should we resolve that problem?
> >> Only reduce the timeout of pq_wait to 100ms? Get rid of
> >> SA_RESTART only during pq_wait as follows?
> >>
> >> remove SA_RESTART
> >> pq_wait()
> >> add SA_RESTART
> >
> > Not sure, will consider. Ask others as well.
>
> I've not got an idea yet. Now (v5), I only reduce the timeout of
> pq_wait to 100ms. Is this sufficient? Do you have any good idea?

To be honest I didn't follow that part of the discussion.

My preferred approach, mentioned earlier in the summer, was to use a
mechanism very similar to LWlocks. A proc queue with semaphores. Minimum
delay, no need for signals. The process doing the wakeup can walk up the
queue until it finds somebody whose wait-for-LSN is higher than has just
been sent/written. Doing it this way also gives us group commit when
synch rep is not enabled.

--
Simon Riggs www.2ndQuadrant.com
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