Re: Better LWLocks with compare-and-swap (9.4)

On 18.05.2013 03:52, Dickson S. Guedes wrote:
>> pgbench -S is such a workload. With 9.3beta1, I'm seeing this
>> profile, when I run "pgbench -S -c64 -j64 -T60 -M prepared" on a
>> 32-core Linux machine:
>>
>> - 64.09% postgres postgres [.] tas - tas - 99.83%
>> s_lock - 53.22% LWLockAcquire + 99.87% GetSnapshotData - 46.78%
>> LWLockRelease GetSnapshotData + GetTransactionSnapshot + 2.97%
>> postgres postgres [.] tas + 1.53% postgres
>> libc-2.13.so [.] 0x119873 + 1.44% postgres postgres
>> [.] GetSnapshotData + 1.29% postgres [kernel.kallsyms] [k]
>> arch_local_irq_enable + 1.18% postgres postgres [.]
>> AllocSetAlloc ...
>
> I'd like to test this here but I couldn't reproduce that perf output
> here in a 64-core or 24-core machines, could you post the changes to
> postgresql.conf and the perf arguments that you used?

Sure, here are the non-default postgresql.conf settings:

name | current_setting
----------------------------+-----------------------------------------
application_name | psql
autovacuum | off
checkpoint_segments | 70
config_file | /home/hlinnakangas/data/postgresql.conf
data_directory | /home/hlinnakangas/data
default_text_search_config | pg_catalog.english
hba_file | /home/hlinnakangas/data/pg_hba.conf
ident_file | /home/hlinnakangas/data/pg_ident.conf
lc_collate | en_US.UTF-8
lc_ctype | en_US.UTF-8
log_timezone | US/Pacific
logging_collector | on
max_connections | 100
max_stack_depth | 2MB
server_encoding | UTF8
shared_buffers | 2GB
synchronous_commit | off
TimeZone | US/Pacific
transaction_deferrable | off
transaction_isolation | read committed
transaction_read_only | off
wal_buffers | 16MB

While pgbench was running, I ran this:

perf record -p 6050 -g -e cpu-clock

to connect to one of the backends. (I used cpu-clock, because the
default cpu-cycles event didn't work on the box)

- Heikki