Re: Postgres Performance Tuning - Mailing list pgsql-performance

Adarsh,

 

[root@s8-mysd-2 8.4SS]# iostat
-bash: iostat: command not found

/usr/bin/iostat

Our application runs by making connections to Postgres Server from different servers and selecting data from one table & insert into remaining tables in a database.

When you are doing bulk inserts you need to tune AUTOVACUUM parameters or Change the autovacuum settings for those tables doing bulk INSERTs. Insert's need analyze.

 

#autovacuum = on                        # Enable autovacuum subprocess?  'on'
                                       # requires track_counts to also be on.
#log_autovacuum_min_duration = -1       # -1 disables, 0 logs all actions and
                                       # their durations, > 0 logs only
                                       # actions running at least this number
                                       # of milliseconds.
#autovacuum_max_workers = 3             # max number of autovacuum subprocesses
#autovacuum_naptime = 1min              # time between autovacuum runs
#autovacuum_vacuum_threshold = 50       # min number of row updates before
                                       # vacuum
#autovacuum_analyze_threshold = 50      # min number of row updates before
                                       # analyze
#autovacuum_vacuum_scale_factor = 0.2   # fraction of table size before vacuum
#autovacuum_analyze_scale_factor = 0.1  # fraction of table size before analyze
#autovacuum_freeze_max_age = 200000000  # maximum XID age before forced vacuum
                                       # (change requires restart)
#autovacuum_vacuum_cost_delay = 20ms    # default vacuum cost delay for
                                       # autovacuum, in milliseconds;
                                       # -1 means use vacuum_cost_delay
#autovacuum_vacuum_cost_limit = -1      # default vacuum cost limit for
                                       # autovacuum, -1 means use
                                       # vacuum_cost_limit

These are all default AUTOVACUUM settings. If you are using PG 8.4 or above, try AUTOVACUUM settings on bulk insert tables for better performance. Also need to tune the 'autovacuum_naptime' 

Eg:-

 ALTER table <table name> SET (autovacuum_vacuum_threshold=xxxxx, autovacuum_analyze_threshold=xxxx);

wal_buffers  //max is 16MB

checkpoint_segment    /// Its very less in your setting

checkpoint_timeout     

temp_buffer  // If application is using temp tables

These parameter will also boost the performance.

Best Regards

Raghavendra

EnterpriseDB Corporation.

 

 

Scott Marlowe wrote:

On Mon, Apr 4, 2011 at 5:34 AM, Adarsh Sharma <adarsh.sharma@orkash.com> wrote: 

Mem:  16299476k total, 16198784k used,   100692k free,    73776k buffers
Swap: 16787884k total,   148176k used, 16639708k free, 15585396k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+
COMMAND
 3401 postgres  20   0 4288m 3.3g 3.3g S    0 21.1   0:24.73
postgres
 3397 postgres  20   0 4286m 119m 119m S    0  0.8   0:00.36
postgres
PLease help me to understand how much memory does 1 Connection Uses and how
to use Server parameters accordingly.   

OK, first, see the 15585396k cached?  That's how much memory your OS
is using to cache file systems etc.  Basically that's memory not being
used by anything else right now, so the OS borrows it and uses it for
caching.

Next, VIRT is how much memory your process would need to load every
lib it might need but may not be using now, plus all the shared memory
it might need, plus it's own space etc.  It's not memory in use, it's
memory that might under the worst circumstances, be used by that one
process.  RES is the amount of memory the process IS actually
touching, including shared memory that other processes may be sharing.Finally, SHR is the amount of shared memory the process is touching.
so, taking your biggest process, it is linked to enough libraries and
shared memory and it's own private memory to add up to 4288Meg.  It is
currently actually touching 3.3G.  Of that 3.3G it is touching 3.3G is
shared with other processes.  So, the difference between RES and SHR
is 0, so the delta, or extra memory it's using besides shared memory
is ZERO (or very close to it, probably dozens or fewer of megabytes).

So, you're NOT running out of memory.  Remember when I mentioned
iostat, vmstat, etc up above?  Have you run any of those?