Need advice on postgresql.conf settings - Mailing list pgsql-performance

Thanks in advance for anything you can do to help.


The real issue is this, we have THE SAME queries taking anywhere from .001 -
90.0 seconds... the server is using 98% of the available RAM at all times
(because of the persistant connections via php), and I don't know what to
do.  Every time I change a .conf setting I feel like it slows it down even
more.... and I can't seem to find the balance.  I'll give you everything
I've got, and I hope to god someone can point out some areas where I could
improve the speed of queries overall.

For months I've been optimizing my queries, and working around places that I
don't need them.  They are so incredibly honed, I couldn't even begin to
explain.... and when there are less than 10 users browsing our sites, they
are LIGHTENING fast... even with 5x the amount of dummy data in the
database(s)... so basically the LARGEST factor in this whole performance
issue that I can find is the number of users browsing the sites at all
times... but lowering shared_buffers to raise max_connections is hurting
performance immensley... so I"m totally lost.... please help!! Bless you!


THE DETAILS:


(for the databases, i'll list only the 'main' tables... as the others are
fairly small)
Database 1:
    5000 'users'
    20,000 'threads'
    500,000 'posts'
    ...
Database 2: (just starting out)
    150 'users'
    150 'entries'
    ...

Hardware :
    Pentium 4 2.44ghz
    1.5gb RAM
    7200rpm SATA

Software:
    Redhat Linux (kernel v. 2.4.21-9.EL)
    Postgresql 7.4.2
    PHP 4.3.6 (using persistant connections to pgsql)

Usage:
    uptime: 12:23:08  up 132 days, 19:16,  2 users,  load average: 19.75,
17.34, 18.86
    roughly 100-200 users connected to our server at any given moment
    roughly 10-15 queries per HTTP page load


----------------------------------------------------------

# -----------------------------
# PostgreSQL configuration file
# -----------------------------
#
# This file consists of lines of the form:
#
#   name = value
#
# (The '=' is optional.) White space may be used. Comments are introduced
# with '#' anywhere on a line. The complete list of option names and
# allowed values can be found in the PostgreSQL documentation. The
# commented-out settings shown in this file represent the default values.
#
# Any option can also be given as a command line switch to the
# postmaster, e.g. 'postmaster -c log_connections=on'. Some options
# can be changed at run-time with the 'SET' SQL command.
#
# This file is read on postmaster startup and when the postmaster
# receives a SIGHUP. If you edit the file on a running system, you have
# to SIGHUP the postmaster for the changes to take effect, or use
# "pg_ctl reload".


#---------------------------------------------------------------------------
# CONNECTIONS AND AUTHENTICATION
#---------------------------------------------------------------------------

# - Connection Settings -

tcpip_socket = true
max_connections = 75
        # note: increasing max_connections costs about 500 bytes of shared
        # memory per connection slot, in addition to costs from
shared_buffers
        # and max_locks_per_transaction.
#superuser_reserved_connections = 2
port = 5432
#unix_socket_directory = ''
#unix_socket_group = ''
#unix_socket_permissions = 0777 # octal
#virtual_host = ''              # what interface to listen on; defaults to
any
#rendezvous_name = ''           # defaults to the computer name

# - Security & Authentication -

#authentication_timeout = 60    # 1-600, in seconds
ssl = true
password_encryption = true
#krb_server_keyfile = ''
#db_user_namespace = false


#---------------------------------------------------------------------------
# RESOURCE USAGE (except WAL)
#---------------------------------------------------------------------------

# - Memory -


shared_buffers = 8192           # min 16, at least max_connections*2, 8KB
each
sort_mem = 8192                 # min 64, size in KB
vacuum_mem = 4096               # min 1024, size in KB

# - Free Space Map -

max_fsm_pages = 20000           # min max_fsm_relations*16, 6 bytes each
max_fsm_relations = 1000        # min 100, ~50 bytes each

# - Kernel Resource Usage -

max_files_per_process = 3052    # min 25
#preload_libraries = ''


#---------------------------------------------------------------------------
# WRITE AHEAD LOG
#---------------------------------------------------------------------------

# - Settings -

fsync = true                    # turns forced synchronization on or off
#wal_sync_method = fsync        # the default varies across platforms:
                                # fsync, fdatasync, open_sync, or
open_datasync
wal_buffers = 192               # min 4, 8KB each

# - Checkpoints -

#checkpoint_segments = 3        # in logfile segments, min 1, 16MB each
#checkpoint_timeout = 300       # range 30-3600, in seconds
#checkpoint_warning = 30        # 0 is off, in seconds
#commit_delay = 0               # range 0-100000, in microseconds
#commit_siblings = 5            # range 1-1000


#---------------------------------------------------------------------------
# QUERY TUNING
#---------------------------------------------------------------------------

# - Planner Method Enabling -

#enable_hashagg = true
#enable_hashjoin = true
#enable_indexscan = true
#enable_mergejoin = true
#enable_nestloop = true
enable_seqscan = false
#enable_sort = true
#enable_tidscan = true

# - Planner Cost Constants -

effective_cache_size = 131072   # typically 8KB each

random_page_cost = 2            # units are one sequential page fetch cost



cpu_tuple_cost = .01            # (same) default .01
cpu_index_tuple_cost = .001     # (same) default .001
cpu_operator_cost = 0.0025      # (same) default .0025

# - Genetic Query Optimizer -

geqo = true
geqo_threshold = 20
#geqo_effort = 1
#geqo_generations = 0
#geqo_pool_size = 0             # default based on tables in statement,
                                # range 128-1024
#geqo_selection_bias = 2.0      # range 1.5-2.0

# - Other Planner Options -

#default_statistics_target = 10 # range 1-1000
#from_collapse_limit = 8
#join_collapse_limit = 8        # 1 disables collapsing of explicit JOINs


#---------------------------------------------------------------------------
# ERROR REPORTING AND LOGGING
#---------------------------------------------------------------------------

# - Syslog -

#syslog = 0                     # range 0-2; 0=stdout; 1=both; 2=syslog
#syslog_facility = 'LOCAL0'
#syslog_ident = 'postgres'

# - When to Log -

client_min_messages = error     # Values, in order of decreasing detail:
                                #   debug5, debug4, debug3, debug2, debug1,
                                #   log, info, notice, warning, error

log_min_messages = error        # Values, in order of decreasing detail:
                                #   debug5, debug4, debug3, debug2, debug1,
                                #   info, notice, warning, error, log,
fatal,
                                #   panic

log_error_verbosity = default   # terse, default, or verbose messages

log_min_error_statement = panic # Values in order of increasing severity:
                                 #   debug5, debug4, debug3, debug2, debug1,
                                 #   info, notice, warning, error,
panic(off)

log_min_duration_statement = -1 # Log all statements whose
                                 # execution time exceeds the value, in
                                 # milliseconds.  Zero prints all queries.
                                 # Minus-one disables.

#silent_mode = false             # DO NOT USE without Syslog!

# - What to Log -

debug_print_parse = false
debug_print_rewritten = false
debug_print_plan = false
debug_pretty_print = false
log_connections = false
log_duration = false
log_pid = false
log_statement = false
log_timestamp = false
log_hostname = false
log_source_port = false


#---------------------------------------------------------------------------
# RUNTIME STATISTICS
#---------------------------------------------------------------------------

# - Statistics Monitoring -

log_parser_stats = false
log_planner_stats = false
log_executor_stats = false
log_statement_stats = false

# - Query/Index Statistics Collector -

stats_start_collector = false
stats_command_string = false
stats_block_level = false
stats_row_level = false
stats_reset_on_server_start = false


#---------------------------------------------------------------------------
# CLIENT CONNECTION DEFAULTS
#---------------------------------------------------------------------------

# - Statement Behavior -

#search_path = '$user,public'   # schema names
#check_function_bodies = true
#default_transaction_isolation = 'read committed'
#default_transaction_read_only = false
#statement_timeout = 0          # 0 is disabled, in milliseconds

# - Locale and Formatting -

#datestyle = 'iso, mdy'
#timezone = unknown             # actually, defaults to TZ environment
setting
#australian_timezones = false
#extra_float_digits = 0         # min -15, max 2
#client_encoding = sql_ascii    # actually, defaults to database encoding

# These settings are initialized by initdb -- they may be changed
lc_messages = 'en_US.UTF-8'             # locale for system error message
strings
lc_monetary = 'en_US.UTF-8'             # locale for monetary formatting
lc_numeric = 'en_US.UTF-8'              # locale for number formatting
lc_time = 'en_US.UTF-8'                 # locale for time formatting

# - Other Defaults -

explain_pretty_print = true
#dynamic_library_path = '$libdir'
#max_expr_depth = 10000         # min 10


#---------------------------------------------------------------------------
# LOCK MANAGEMENT
#---------------------------------------------------------------------------

#deadlock_timeout = 1000        # in milliseconds
#max_locks_per_transaction = 64 # min 10, ~260*max_connections bytes each


#---------------------------------------------------------------------------
# VERSION/PLATFORM COMPATIBILITY
#---------------------------------------------------------------------------

# - Previous Postgres Versions -

#add_missing_from = true
regex_flavor = advanced         # advanced, extended, or basic
#sql_inheritance = true

# - Other Platforms & Clients -

#transform_null_equals = false


------
I've been tweaking the postgresql.conf file for about 5 hours... just today.
We've had problems in the past (and I've also emailed this list in the past,
but perhaps I failed to ask the right questions)....

I guess I need some help with the postgresql configuration file.  I would
like to start off by asking that you not link me to the same basic .CONF
overview, as what I really need at this point is real-world experience and
wisdom, as opposed to cold, poorly documented, and incredibly abstract
(trial-and-error) type manual entries.