Re: [PERFORM] Stats collector constant I/O
On May 14, 2014 9:19 PM, Craig James cja...@emolecules.com wrote: Day and night, the postgres stats collector process runs at about 20 MB/sec output. vmstat shows this: $ vmstat 2 procs ---memory-- ---swap-- -io -system-- cpu r b swpd free buff cache si sobibo in cs us sy id wa 0 0 55864 135740 123804 1071292846 445 264200 5 1 92 2 1 0 55864 134820 123804 1071301200 0 34880 540 338 1 1 98 0 0 0 55864 135820 123812 1071289600 0 20980 545 422 1 1 98 0 iotop(1) shows that it's the stats collector, running at 20 MB/sec. This is normal for 9.2 and below if you have hundreds of databases in the cluster. Cheers, Jeff
Re: [PERFORM] Stats collector constant I/O
Hello we had similar issue - you can try to move statfile to ramdisc http://serverfault.com/questions/495057/too-much-i-o-generated-by-postgres-stats-collector-process Regards Pavel Stehule 2014-05-15 6:18 GMT+02:00 Craig James cja...@emolecules.com: Day and night, the postgres stats collector process runs at about 20 MB/sec output. vmstat shows this: $ vmstat 2 procs ---memory-- ---swap-- -io -system-- cpu r b swpd free buff cache si sobibo in cs us sy id wa 0 0 55864 135740 123804 1071292846 445 264200 5 1 92 2 1 0 55864 134820 123804 1071301200 0 34880 540 338 1 1 98 0 0 0 55864 135820 123812 1071289600 0 20980 545 422 1 1 98 0 iotop(1) shows that it's the stats collector, running at 20 MB/sec. Is this normal? Craig
Re: [PERFORM] Stats collector constant I/O
On 15.5.2014 06:18, Craig James wrote: Day and night, the postgres stats collector process runs at about 20 MB/sec output. vmstat shows this: $ vmstat 2 procs ---memory-- ---swap-- -io -system-- cpu r b swpd free buff cache si sobibo in cs us sy id wa 0 0 55864 135740 123804 1071292846 445 264200 5 1 92 2 1 0 55864 134820 123804 1071301200 0 34880 540 338 1 1 98 0 0 0 55864 135820 123812 1071289600 0 20980 545 422 1 1 98 0 iotop(1) shows that it's the stats collector, running at 20 MB/sec. Which PostgreSQL version are you running? And how many databases / objects (tables, indexes) are there? With versions up to 9.1, and large number of objects this is quite normal. The file size is proportional to the number of objects, and may get written quite frequently. The newer versions (since 9.2) have per-database file, which usually significantly decreases the load - both CPU and I/O. But if you have all the objects are in a single database, this is not going to help. I'd recommend moving the stat directory to tmpfs (i.e. memory-based filesystem) - this improves the I/O load, but it may still consume nontrivial amount of CPU time to read/write it. Tomas -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
