Re: WAL recycling, ext3, Linux 2.4.18

Doug Fields <dfields-pg-general@pexicom.com> writes:
> I'm still trying to track down my very odd periodic pauses/hangs in
> PostgreSQL 7.2.1.
> I've localized it to what seems to be the "recycled transaction log file"
> lines in the log file. Whenever this happens, a whole bunch of queries
> which were "on hold" (just sitting there, as can be seen in
> pg_stat_activity, when they usually execute in fractions of a second) come
> back to life and finish very quickly.

Hm.  That would be from the tail end of a checkpoint operation.  If you
do a CHECKPOINT command manually, do you get a similar hangup?

What are the stuck queries doing exactly?  Can you attach to a few of the
stuck backends with gdb and get stack traces?

> 1) Is there any known bad interactions with ext3fs and PostgreSQL?

Dunno.  The CHECKPOINT would probably create a significant number of
disk write requests, followed by a sync() request.  If that could
monopolize an ext3 filesystem for a long time, perhaps that would
explain your problem.  But I haven't heard similar complaints before.

What do you have shared_buffers set to?

            regards, tom lane