There are many processes created and died frequently during PostgreSQl idle

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От	高健
Тема	There are many processes created and died frequently during PostgreSQl idle
Дата	24 мая 2013 г. 05:50:52
Msg-id	CAL454F2_t7fgKqWWY7d6NEHo2xv6PvD7kGSk3Ve_9-g9XGvRCQ@mail.gmail.com обсуждение исходный текст
Ответы	Re: There are many processes created and died frequently during PostgreSQl idle (Jov <amutu@amutu.com>)
Список	pgsql-general

Дерево обсуждения

Hello all:

I found that during postgresql running, there are so many processes being created and then died.

I am interested in the reason.

Here is the detail:

I installed from postgresql-9.2.1.tar.bz2.

I put some debug code in fd.c 's PathNameOpenFile function:

fprintf(stderr,"+++While Calling PathNameOpenFile pid=%d.....",getpid();

fprintf(stderr,"VfdCache Address is: %p \n\n",VfdCache);

When it run, I open two termianal using psql(pid=22109 and pid=22114), then I can got information like this:

[postgres@lex pgsql]$ ./bin/pg_ctl -D ./data start

server starting

[postgres@lex pgsql]$ LOG: database system was shut down at 2013-05-24 09:28:59 CST

LOG: autovacuum launcher started

+++While Calling PathNameOpenFile pid=22106.....VfdCache Address is: 0xbfb3320

LOG: database system is ready to accept connections

+++While Calling PathNameOpenFile pid=22109.....VfdCache Address is: 0xbfb2de0

+++While Calling PathNameOpenFile pid=22114.....VfdCache Address is: 0xbfba400

+++While Calling PathNameOpenFile pid=22120.....VfdCache Address is: 0xbfe6700

+++While Calling PathNameOpenFile pid=22127.....VfdCache Address is: 0xbfe6700

+++While Calling PathNameOpenFile pid=22134.....VfdCache Address is: 0xbfe6700

+++While Calling PathNameOpenFile pid=22142.....VfdCache Address is: 0xbfe6700

+++While Calling PathNameOpenFile pid=22149.....VfdCache Address is: 0xbfe6700

+++While Calling PathNameOpenFile pid=22156.....VfdCache Address is: 0xbfe6700

+++While Calling PathNameOpenFile pid=22165.....VfdCache Address is: 0xbfe6700

+++While Calling PathNameOpenFile pid=22171.....VfdCache Address is: 0xbfe6700

+++While Calling PathNameOpenFile pid=22178.....VfdCache Address is: 0xbfe6700

But when I grep process information using ps command, I can't find process such like 22120,22127,22134,22142,22149,22156,22178.

And the output is growing longer and longer...

[root@lex ~]# ps -ef | grep post

root 4641 4621 0 08:28 pts/3 00:00:00 su - postgres

postgres 4642 4641 0 08:28 pts/3 00:00:00 -bash

root 4709 4688 0 08:28 pts/4 00:00:00 su - postgres

postgres 4710 4709 0 08:28 pts/4 00:00:00 -bash

root 4772 4751 0 08:29 pts/5 00:00:00 su - postgres

postgres 4773 4772 0 08:29 pts/5 00:00:00 -bash

postgres 22101 1 0 09:45 pts/3 00:00:00 /usr/local/pgsql/bin/postgres -D ./data

postgres 22103 22101 0 09:45 ? 00:00:00 postgres: checkpointer process

postgres 22104 22101 0 09:45 ? 00:00:00 postgres: writer process

postgres 22105 22101 0 09:45 ? 00:00:00 postgres: wal writer process

postgres 22106 22101 0 09:45 ? 00:00:00 postgres: autovacuum launcher process

postgres 22107 22101 0 09:45 ? 00:00:00 postgres: stats collector process

postgres 22108 4710 0 09:45 pts/4 00:00:00 ./psql

postgres 22109 22101 0 09:45 ? 00:00:00 postgres: postgres postgres [local] idle

postgres 22113 4773 0 09:46 pts/5 00:00:00 ./psql

postgres 22114 22101 0 09:46 ? 00:00:00 postgres: postgres postgres [local] idle

root 22187 6429 0 09:55 pts/6 00:00:00 grep post

[root@lex ~]#

So I think that some process is created and then quickly died . But would somebody can kindly say what are the purpose of those process?

How about using one worker process and keep it be alive?

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