Process 11812 still waiting for ExclusiveLock on extension of relation

Howdy,

I've got a couple of tables that are taking a little longer than normal to extend, resulting
in some slow inserts.

They're fairly large tables, ~200GB pg_total_relation_size (90GB for just the table)

I suspect that this is related to a sustained heavy load that would stop autovacuum from
getting at this table... Does that sound plausible?

I'm wondering what options I have to smooth over these episodes / speed up the extensions.
I'm thinking of something like, CLUSTER or VACUUM FULL (those take quite a run so I'd like
some direction on it before i TiaS =) )

I suspect that Partitioning would help. Any other ideas?

Jul 17 08:11:52 perf: [3-1] user=test,db=perf LOG: process 11812 still waiting for ExclusiveLock
on extension of relation 60777 of database 16387 after 1000.270 ms

System resouces were fine:

PGDATA
------
07/17/12 08:11:48
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
dm-2 1.20 3085.20 77.20 3994.20 15363.20 56680.00 17.69 15.57 3.82 0.06 26.22

07/17/12 08:11:53
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
dm-2 0.40 2097.20 51.80 2610.20 10344.00 37659.20 18.03 5.23 1.96 0.05 14.28

PGXLOG
------
07/17/12 08:11:48
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
dm-4 0.00 3958.20 0.00 600.40 0.00 36449.60 60.71 0.44 0.74 0.73 43.54

07/17/12 08:11:53
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
dm-4 0.00 2905.20 0.00 403.40 0.00 26492.80 65.67 0.32 0.80 0.79 31.96

CPU
------
CPU %user %nice %system %iowait %steal %idle
08:11:48 all 24.49 0.00 3.19 1.17 0.00 71.15
08:11:53 all 17.53 0.00 3.13 0.68 0.00 78.65