Re: SMP-PPC spinlocks in 7.2.4?

eric soroos <eric-psql(at)soroos(dot)net> writes:
> The last few days, I've been dealing with a client who has drastically upped their usage of the database and in doing so is causing deadlocks. I was running 7.2 or 7.2.1, I upgraded to a locally compiled 7.2.4. I've run a vacuum full on the databases.

> Sometimes the clients have a ps ax status of async_notify, sometimes there's just a stack of selects and updates that get hung. (I'd estimate 6 deadlocks since Saturday). It seems to coincide with times of extra activity, such as when the databases are being backed up with pg_dump.

Hm. Do they use query-cancels at all? The reference to async_notify
makes me wonder if this is related to the recently-discovered
async_notify bug that could prevent fast-mode shutdowns. I'm not
certain how that might lead to an apparent deadlock, but a query cancel
arriving during async_notify would surely improve the odds of trouble.

If you don't mind running a slightly customized version, you might try
back-patching this fix:
http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/commands/async.c.diff?r1=1.91&r2=1.91.2.1
into 7.2.4 and see if that improves matters.

If it doesn't, I'd be interested to look into the matter, but I'd
probably need access to the machine to see what is going on.

> I've also noticed the following in cron logs from nightly vacuums

> NOTICE: Rel pg_attribute: Uninitialized page 59 - fixing
> NOTICE: Rel pg_attribute: Uninitialized page 60 - fixing

These are harmless.

> Is there anything I can do to debug this? I'm willing to give it a
> shot, but I'm also rapidly preparing a single proc linux/intel machine
> to take over db duties.

I think you're mistaken to be blaming the hardware...

regards, tom lane