Re: Performance Woes

["Ralph Mason" <ralph.mason@xxxxxxxxxxx>]

 

 

From: pgsql-performance-owner@xxxxxxxxxxxxxx [mailto:pgsql-performance-owner@xxxxxxxxxxxxxx] On Behalf Of CAJ CAJ
Sent: 10 May 2007 12:26
To: Ralph Mason
Cc: pgsql-performance@xxxxxxxxxxxxxx
Subject: Re: [PERFORM] Performance Woes

 

 

I have several databases.  They are each about 35gb in size and have about 10.5K relations (count from pg_stat_all_tables) in them.  Pg_class is about 26k rows and the data directory contains about 70k files.  These are busy machines, they run about 50 xactions per second, ( aproxx insert / update / delete about 500 rows per second).

We started getting errors about the number of open file descriptors

: 2007-05-09 03:07:50.083 GMT 1146975740: LOG:  53000: out of file descriptors: Too many open files; release and retry

2007-05-09 03:07:50.083 GMT 1146975740: CONTEXT:  SQL statement "insert ….. "

        PL/pgSQL function "trigfunc_whatever" line 50 at execute statement

2007-05-09 03:07:50.083 GMT 1146975740: LOCATION:  BasicOpenFile, fd.c:471

2007-05-09 03:07:50.091 GMT 0: LOG:  00000: duration: 12.362 ms

2007-05-09 03:07:50.091 GMT 0: LOCATION:  exec_simple_query, postgres.c:1090

 

So  we decreased the max_files_per_process to 800.  This took care of the error *BUT* about quadrupled  the IO wait that is happening on the machine. It went from a peek of about 50% to peeks of over 200% (4 processor machines, 4 gigs ram, raid).  The load on the machine remained constant.

>What version of Pg/OS? What is your hardware config?

>I had seen these errors with earlier versions of Pg 7.4.x which was fixed in later releases according to the changelogs

"PostgreSQL 8.1.4 on x86_64-redhat-linux-gnu, compiled by GCC x86_64-redhat-linux-gcc (GCC) 4.1.0 20060304 (Red Hat 4.1.0-3)"

 

su postgres -c 'ulimit -a'

 

core file size          (blocks, -c) 0

data seg size           (kbytes, -d) unlimited

max nice                        (-e) 0

file size               (blocks, -f) unlimited

pending signals                 (-i) 49152

max locked memory       (kbytes, -l) 32

max memory size         (kbytes, -m) unlimited

open files                      (-n) 1000000

pipe size            (512 bytes, -p) 8

POSIX message queues     (bytes, -q) 819200

max rt priority                 (-r) 0

stack size              (kbytes, -s) 10240

cpu time               (seconds, -t) unlimited

max user processes              (-u) 49152

virtual memory          (kbytes, -v) unlimited

file locks                      (-x) unlimited

file locks                      (-x) unlimited

Seems like I should be able to use lots and lots of open files.

Machines are quad processor opterons, 4gb ram with raid 5 data and logging to a raid 0.

Ralph

 

--
Internal Virus Database is out-of-date.
Checked by AVG Free Edition.
Version: 7.5.432 / Virus Database: 268.15.9/573 - Release Date: 05/12/2006 16:07