Re: Reduce ProcArrayLock contention

On 08/07/2015 10:47 AM, Amit Kapila wrote:
>> Fyi, there is something in pgbench that has caused a testing regression -
>> havn't tracked down what yet.
>>
>> Against 9.6 server (846f8c9483a8f31e45bf949db1721706a2765771)
>>
>> 9.6 pgbench:
>> ------------
>> progress: 10.0 s, 53525.0 tps, lat 1.485 ms stddev 0.523
>> progress: 20.0 s, 15750.6 tps, lat 5.077 ms stddev 1.950
>> ...
>> progress: 300.0 s, 15636.9 tps, lat 5.114 ms stddev 1.989
>>
>> 9.5 pgbench:
>> ------------
>> progress: 10.0 s, 50119.5 tps, lat 1.587 ms stddev 0.576
>> progress: 20.0 s, 51413.1 tps, lat 1.555 ms stddev 0.553
>> ...
>> progress: 300.0 s, 52951.6 tps, lat 1.509 ms stddev 0.657
>>
>>
>> Both done with -c 80 -j 80 -M prepared -P 10 -T 300.
>>
>
> I will look into it.
> Could you please share some of the settings used for test like
> scale_factor in pgbench and shared_buffers settings or if you
> have changed any other default setting in postgresql.conf?
>

Compiled with

export CFLAGS="-O -fno-omit-frame-pointer" && ./configure --prefix
/opt/postgresql-9.6 --with-openssl --with-gssapi --enable-debug

Scale factor is 3000

shared_buffers = 64GB
max_prepared_transactions = 10
work_mem = 64MB
maintenance_work_mem = 512MB
effective_io_concurrency = 4
max_wal_size = 100GB
effective_cache_size = 160GB

Machine has 28C / 56T with 256Gb mem, and 2 x RAID10 (SSD)

Note, that the server setup is the same in both run, just the pgbench
version is changed. Latency and stddev goes up between 10.0s and 20.0s
when using 9.6 pgbench.

Best regards,
Jesper