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=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@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?
