On Mon, Jun 13, 2011 at 8:10 PM, Jeff Janes <[email protected]> wrote:
> On Sun, Jun 12, 2011 at 2:39 PM, Robert Haas <[email protected]> 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
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