Re: There are many processes created and died frequently during PostgreSQl idle

From: Jov <amutu(at)amutu(dot)com>
To: 高健 <luckyjackgao(at)gmail(dot)com>
Cc: pgsql-general <pgsql-general(at)postgresql(dot)org>
Subject: Re: There are many processes created and died frequently during PostgreSQl idle
Date: 2013-05-24 05:47:44
Message-ID: CADyrUxOhUn1D1vn09c7cKxs8bMkQ0-FaAjYsXKDtFRyQ58DXmg@mail.gmail.com
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the process you see may be autovacuum worker process,you can tune the
log_autovacuum_min_duration
to log the autovacuum activities and check if the pids match
http://www.postgresql.org/docs/9.2/static/runtime-config-autovacuum.html

2013/5/24 高健 <luckyjackgao(at)gmail(dot)com>

> 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(at)lex pgsql]$ ./bin/pg_ctl -D ./data start
> server starting
> [postgres(at)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=22109.....VfdCache Address is:
> 0xbfb2de0
>
> +++While Calling PathNameOpenFile pid=22109.....VfdCache Address is:
> 0xbfb2de0
>
> +++While Calling PathNameOpenFile pid=22109.....VfdCache Address is:
> 0xbfb2de0
>
> +++While Calling PathNameOpenFile pid=22109.....VfdCache Address is:
> 0xbfb2de0
>
> +++While Calling PathNameOpenFile pid=22109.....VfdCache Address is:
> 0xbfb2de0
>
> +++While Calling PathNameOpenFile pid=22109.....VfdCache Address is:
> 0xbfb2de0
>
> +++While Calling PathNameOpenFile pid=22109.....VfdCache Address is:
> 0xbfb2de0
>
> +++While Calling PathNameOpenFile pid=22109.....VfdCache Address is:
> 0xbfb2de0
>
> +++While Calling PathNameOpenFile pid=22109.....VfdCache Address is:
> 0xbfb2de0
>
> +++While Calling PathNameOpenFile pid=22109.....VfdCache Address is:
> 0xbfb2de0
>
> +++While Calling PathNameOpenFile pid=22109.....VfdCache Address is:
> 0xbfb2de0
>
> +++While Calling PathNameOpenFile pid=22109.....VfdCache Address is:
> 0xbfb2de0
>
> +++While Calling PathNameOpenFile pid=22109.....VfdCache Address is:
> 0xbfb2de0
>
> +++While Calling PathNameOpenFile pid=22109.....VfdCache Address is:
> 0xbfb2de0
>
> +++While Calling PathNameOpenFile pid=22114.....VfdCache Address is:
> 0xbfba400
>
> +++While Calling PathNameOpenFile pid=22114.....VfdCache Address is:
> 0xbfba400
>
> +++While Calling PathNameOpenFile pid=22114.....VfdCache Address is:
> 0xbfba400
>
> +++While Calling PathNameOpenFile pid=22114.....VfdCache Address is:
> 0xbfba400
>
> +++While Calling PathNameOpenFile pid=22120.....VfdCache Address is:
> 0xbfe6700
>
> +++While Calling PathNameOpenFile pid=22120.....VfdCache Address is:
> 0xbfe6700
>
> +++While Calling PathNameOpenFile pid=22120.....VfdCache Address is:
> 0xbfe6700
>
> +++While Calling PathNameOpenFile pid=22127.....VfdCache Address is:
> 0xbfe6700
>
> +++While Calling PathNameOpenFile pid=22127.....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=22134.....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=22142.....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=22149.....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=22156.....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=22165.....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=22171.....VfdCache Address is:
> 0xbfe6700
>
> +++While Calling PathNameOpenFile pid=22171.....VfdCache Address is:
> 0xbfe6700
>
> +++While Calling PathNameOpenFile pid=22178.....VfdCache Address is:
> 0xbfe6700
>
> +++While Calling PathNameOpenFile pid=22178.....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(at)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(at)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?
>

--
Jov
blog: http:amutu.com/blog <http://amutu.com/blog>

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