HammerDB Best Practice for PostgreSQL Performance and Scalability

This post gives a HOWTO guide on system configuration for achieving top levels of performance with the HammerDB PostgreSQL TPC-C test.  As an Intel employee (#IAMINTEL) the examples are taken from a PostgreSQL on Linux on Intel system, the approach is the same for whatever system you are testing although some of the settings you see may be different.
Firstly for system choice a 2 socket system is optimal for PostgreSQL OLTP performance at the time of writing. This limitation is at the database level rather than the hardware level, nevertheless with up to date hardware (from mid-2018) PostgreSQL on a 2 socket system can be expected to deliver more than 2M PostgreSQL TPM and 1M NOPM with the HammerDB TPC-C test. 


On the 2 socket system you will need I/O that is able to keep up with writing to the WAL – An example is an NVME PCIe SSD formatted as an XFS file system and mounted as below: 

/dev/nvme0n1p1                                /mnt/ssd        xfs     noatime

The OS  username you are using it can be anything but for people familair with Oracle this becomes the equivalent of the system username.  Many people use postgres.

CPU Configuration

Make sure that your CPU is configured for optimal performance. To do this make sure that the Linux tools package is installed. If so there are a number of tools under the /usr/lib/linux-tools directory under the specific kernel name. 

# ls
acpidbg  cpupower  perf  turbostat  usbip  usbipd  x86_energy_perf_policy
With these installed set the cpufreq governor to performance as follows:
# ./cpupower frequency-set --governor=performance
Setting cpu: 0
Setting cpu: 1
Setting cpu: 2
Check that the settings have been applied and the frequency settings as expected. From the following output key things to check are that the driver is shown as intel_pstate (for Intel CPUs), the governor shows as performance, the frequency range goes to the maximum frequency for the CPU and boost state is supported (if your CPU supports turbo boost). 
# ./cpupower frequency-info
analyzing CPU 0:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency:  Cannot determine or is not supported.
  hardware limits: 1000 MHz - 3.80 GHz
  available cpufreq governors: performance powersave
  current policy: frequency should be within 1000 MHz and 3.80 GHz.
                  The governor "performance" may decide which speed to use
                  within this range.
  current CPU frequency: Unable to call hardware
  current CPU frequency: 1.99 GHz (asserted by call to kernel)
  boost state support:
    Supported: yes
    Active: yes

Also check that the idle settings are enabled and (for Intel CPUs) that the intel_idle driver is used. Note that the pstate and cstate drivers work together to provide the most efficient use of turbo boost. Initially it is best leave all of these states enabled. Disabling all C-states or Idle states is likely to reduce overall performance by reducing the available turbo frequency. You can experiment with the C-states between ‘all or nothing’ to find the optimal settings. 

# ./cpupower idle-set --enable-all
# ./cpupower idle-info
CPUidle driver: intel_idle
CPUidle governor: menu
analyzing CPU 0:
Number of idle states: 4
Available idle states: POLL C1 C1E C6
Latency: 0
Usage: 10736
Duration: 29182086
You are not quite done. There is another tool in the directory called x86_energy_perf_policy that determines how the boost states are used. By default this is set to normal so you will want to set it to performance. 
# ./x86_energy_perf_policy -rcpu0: EPB 6
cpu0: HWP_REQ: min 38 max 38 des 0 epp 0 window 0x0 (0*10^0us) use_pkg 0
cpu0: HWP_CAP: low 7 eff 10 guar 25 high 38
cpu1: EPB 6
# ./x86_energy_perf_policy performance
# ./x86_energy_perf_policy -rcpu0: EPB 0
cpu0: HWP_REQ: min 38 max 38 des 0 epp 0 window 0x0 (0*10^0us) use_pkg 0
cpu0: HWP_CAP: low 7 eff 10 guar 25 high 38
cpu1: EPB 0
As the name indicates the turbostat tool can be used to monitor the CPU turbo frequencies. 
Huge Page Memory Configuration

For the memory we need to set Huge Pages – so as root add the following line to /etc/sysctl.conf we are going to create 64GB of buffers by adding the vm.nr_hugepages line (Huge Pages are 2MB in size). 

vm.swappiness = 0
kernel.sem = 250 32000 100 128
fs.file-max = 6815744
net.ipv4.ip_local_port_range = 9000 65500
net.core.rmem_default = 262144
net.core.rmem_max = 4194304
net.core.wmem_default = 262144
net.core.wmem_max = 1048576
fs.aio-max-nr = 1048576
vm.nr_hugepages = 35000
 Also edit /etc/security/limits.conf and add the following:
postgres soft memlock 100000000
postgres hard memlock 100000000
Now run the command “sysctl –p” as root, when the database is running you will see the memory allocated from huge pages. 
cat /proc/meminfo
HugePages_Total:   35000
HugePages_Free:     6588
HugePages_Rsvd:     4572

To reiterate this will only be when you have reached the stage of starting the database, so firstly you will need to install the software.

Install PostgreSQL from Source
Make sure that you have the necessary software to compile PostgreSQL from source, download the postgresql source and extract it to your PostgreSQL file system configured above. Although 9.6.5 has been used here, feel free to download and use the latest release. 
postgres:/mnt/ssd/postgresqlsrc$ ls
pgsql  postgresql-9.6.5  postgresql-9.6.5.tar
 Find and change change the file pg_config.h (after having run configure first)
find . -name pg_config.h -print

 So it looks like below, this will set the WAL file size to be 1GB instead of the default 16MB. 

/* XLOG_SEG_SIZE is the size of a single WAL file. This must be a power of 2
   and larger than XLOG_BLCKSZ (preferably, a great deal larger than
   XLOG_BLCKSZ). Changing XLOG_SEG_SIZE requires an initdb. */
#define XLOG_SEG_SIZE (1024 * 1024 * 1024)
The default location for the install is in /usr/local/pgsql so the easiest way to configure is to set a symbolic link to a directory from your ssd to this location using the “ln –s” command
pgsql -> /mnt/ssd/postgresqlsrc/pgsql
postgres:/mnt/ssd/postgresqlsrc$ ls -ltr /usr/local
total 32
lrwxrwxrwx 1 root root   28 Oct 11 03:41 pgsql -> /mnt/ssd/postgresqlsrc/pgsql
Now follow the steps previously to compile PostgreSQL from source. When you do “make install” it will create the binaries in this location.  You also need to create a new directory called “data” and if all went well you should now have a directory that looks like this:
postgres:/usr/local/pgsql$ ls
bin  data  include  lib  share
Configure PostgreSQL
Run initdb from the bin directory specifying the data directory
./bin/initdb -D ./data
This creates your database with the username of the OS user you are using as the superuser. Now edit 2 configuration files postgresql.conf and pg_hba.conf. 
For Postgresql.conf you have a number of options. It is your test so you can set the options as you see fit. Remember to set huge_pages=on and note that whereas wal_level minimal=minimal and synchronous_commit=off will give you the best WAL performance for a test it may not be what you would want in a production environment. (and you can run further tests to quantify the impact of these options). 
postgres:/mnt/ssd/postgresqlsrc/pgsql/data$ more postgresql.conf
listen_addresses =''              # what IP address(es) to listen on;
port = 5432                             # (change requires restart)
max_connections = 256                   # (change requires restart)
shared_buffers = 64000MB                        # min 128kB
huge_pages = on                 # on, off, or try
temp_buffers = 4000MB                   # min 800kB
work_mem = 4000MB                               # min 64kB
maintenance_work_mem = 512MB            # min 1MB
autovacuum_work_mem = -1                # min 1MB, or -1 to use maintenance_work_mem
max_stack_depth = 7MB                   # min 100kB
dynamic_shared_memory_type = posix      # the default is the first option
max_files_per_process = 4000            # min 25
effective_io_concurrency = 32           # 1-1000; 0 disables prefetching
wal_level = minimal                     # minimal, archive, hot_standby, or logical
synchronous_commit = off                # synchronization level;
wal_buffers = 512MB                     # min 32kB, -1 sets based on shared_buffers
#checkpoint_segments = 256              # in logfile segments, min 1, 16MB each
checkpoint_timeout = 1h         # range 30s-1h
checkpoint_completion_target = 1        # checkpoint target duration, 0.0 - 1.0
checkpoint_warning = 0          # 0 disables
log_min_messages = error                # values in order of decreasing detail:
log_min_error_statement = error # values in order of decreasing detail:
log_timezone = 'GB'
autovacuum = off                        # Enable autovacuum subprocess?  'on'
datestyle = 'iso, dmy'
timezone = 'GB'
lc_messages = 'en_GB.UTF-8'                     # locale for system error message
lc_monetary = 'en_GB.UTF-8'                     # locale for monetary formatting
lc_numeric = 'en_GB.UTF-8'                      # locale for number formatting
lc_time = 'en_GB.UTF-8'                         # locale for time formatting
default_text_search_config = 'pg_catalog.english'
max_locks_per_transaction = 64          # min 10
max_pred_locks_per_transaction = 64     # min 10
Also change the pg_hba.conf and add the ip addresses for your test server and load testing client running HammerDB.
# TYPE  DATABASE        USER            ADDRESS                 METHOD
# "local" is for Unix domain socket connections only
local   all             all                                     trust
# IPv4 local connections:
host    all             all               trust
# IPv6 local connections:
host    all             all             ::1/128                 trust
host    all             all           trust
host    all             all           trust
# Allow replication connections from localhost, by a user with the
# replication privilege.
#local   replication     postgres                                trust
#host    replication     postgres            trust
#host    replication     postgres       ::1/128                 trust
Start the PostgreSQL Database

Start the database as follows:

./bin/pg_ctl start -D ./data

And check it is running (remember to check the huge page allocation as well).
postgres:/usr/local/pgsql$ ps -ef | grep post
postgres    201539      1  0 Sep19 ?        00:00:00 /mnt/ssd/postgresqlsrc/pgsql/bin/postgres -D ./data
postgres    201541 201539  0 Sep19 ?        00:00:57 postgres: checkpointer process
postgres    201542 201539  0 Sep19 ?        00:00:02 postgres: writer process
postgres    201543 201539  0 Sep19 ?        00:03:18 postgres: wal writer process
postgres   201544 201539  0 Sep19 ?        00:00:04 postgres: stats collector process
You can stop the database as follows:
./bin/pg_ctl stop -D ./data
 Now login set the password for the “superuser” note how this takes the name from the OS user so in this case postgres.
postgres:/usr/local/pgsql$ ./bin/psql -U postgres -d postgres
psql (9.6.5)
Type "help" for help.
postgres=# alter role postgres password 'postgres';
Use –W to test the password
postgres:/usr/local/pgsql$ ./bin/psql -U postgres -d postgres -W
Password for user postgres:
psql (9.6.5)
Type "help" for help.
Configure the HammerDB Client

Download and install HammerDB on a test client system, another 2 socket server is ideal. You need the client libraries so you can either copy the postgres lib directory you have just compiled or compile from source again on this host – you don’t need to create a database or set the config files. Then add the library to the library path:

postgres:~$ export LD_LIBRARY_PATH=/usr/local/pgsql/lib:$LD_LIBRARY_PATH

and check that it loads with a librarycheck test.

$ ./hammerdbcli
HammerDB CLI v3.1
Copyright (C) 2003-2018 Steve Shaw
Type "help" for a list of commands
The xml is well-formed, applying configuration
Checking database library for PostgreSQL
Success ... loaded library Pgtcl for PostgreSQL
Create the Schema and Run the Test
You can now start HammerDB on the client and from the Database options choose PostgreSQL. Follow the HammerDB documentation to build the schema and run the test. Do not select the EnterpriseDB Oracle compatible schema as you installed the software from source. Creating an 800 Warehouse schema is a good starting point, the data should load quickly but note that creating indexes can take up to 20 mins or so this is to be expected. If you have a system with an up to date CPU (as of mid-2018), enough memory and everything installed on a fast SSD then more than 2M PostgreSQL TPM and more than 1M NOPM should be achievable.

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