On Mon, Jun 13, 2011 at 8:10 PM, Jeff Janes <jeff.janes@gmail.com> wrote:
> On Sun, Jun 12, 2011 at 2:39 PM, Robert Haas <robertmhaas@gmail.com> wrote:
> ...
>>
>> Profiling reveals that the system spends enormous amounts of CPU time
>> in s_lock. LWLOCK_STATS reveals that the only lwlock with significant
>> amounts of blocking is the BufFreelistLock;
>
> This is curious. Clearly the entire working set fits in RAM, or you
> wouldn't be getting number like this. But does the entire working set
> fit in shared_buffers? If so, you shouldn't see any traffic on
> BufFreelistLock once all the data is read in. I've only seen
> contention here when all data fits in OS cache memory but not in
> shared_buffers.
Yeah, that does seem odd:
rhaas=# select pg_size_pretty(pg_database_size(current_database()));pg_size_pretty
----------------1501 MB
(1 row)
rhaas=# select pg_size_pretty(pg_table_size('pgbench_accounts'));pg_size_pretty
----------------1281 MB
(1 row)
rhaas=# select pg_size_pretty(pg_table_size('pgbench_accounts_pkey'));pg_size_pretty
----------------214 MB
(1 row)
rhaas=# show shared_buffers;shared_buffers
----------------8GB
(1 row)
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
