oom_adjust_v2.patch

*** a/contrib/start-scripts/linux
--- b/contrib/start-scripts/linux
***************
*** 53,58 **** DAEMON="$prefix/bin/postmaster"
--- 53,63 ----
  # What to use to shut down the postmaster
  PGCTL="$prefix/bin/pg_ctl"
  
+ # Adjust oom_adj on linux to avoid the postmaster from be killed
+ # note you probably want to compile postgres with -DLINUX_OOM_ADJ=0
+ # so that regular backends will be killed on oom
+ OOM_ADJ=-17
+ 
  set -e
  
  # Only start if we can find the postmaster.
***************
*** 62,67 **** test -x $DAEMON || exit 0
--- 67,73 ----
  case $1 in
    start)
  	echo -n "Starting PostgreSQL: "
+ 	echo $OOM_ADJ > /proc/self/oom_adj
  	su - $PGUSER -c "$DAEMON -D '$PGDATA' &" >>$PGLOG 2>&1
  	echo "ok"
  	;;
*** a/src/backend/postmaster/autovacuum.c
--- b/src/backend/postmaster/autovacuum.c
***************
*** 1403,1408 **** StartAutoVacWorker(void)
--- 1403,1411 ----
  			/* Lose the postmaster's on-exit routines */
  			on_exit_reset();
  
+ 			/* allow us to be killed on oom */
+ 			oom_adjust();
+ 
  			AutoVacWorkerMain(0, NULL);
  			break;
  #endif
*** a/src/backend/postmaster/fork_process.c
--- b/src/backend/postmaster/fork_process.c
***************
*** 66,68 **** fork_process(void)
--- 66,97 ----
  }
  
  #endif   /* ! WIN32 */
+ 
+ #if defined(__linux__) && defined(LINUX_OOM_ADJ)
+ /*
+  * By default linux really likes to kill the postmaster on oom.
+  * Because linux does not take SYSV shared mem into account it
+  * (almost) always will SIGKILL the postmaster on an oom event.
+  *
+  * In the event you started the postmaster under a low (negative)
+  * oom_adj.  This will adjust regular backends, autovac and archivers
+  * to LINUX_OOM_ADJ on fork().  Allowing them to be killed in an oom
+  * event.
+  *
+  * Later we might add other OS oom type stuff here.
+  */
+ void
+ oom_adjust(void)
+ {
+ 	FILE *oom = fopen("/proc/self/oom_adj", "w");
+ 
+ 	/* ignore errors we dont really care */
+ 	if (oom)
+ 	{
+ 		fprintf(oom, "%d\n", LINUX_OOM_ADJ);
+ 		fclose(oom);
+ 	}
+ }
+ #else
+ void oom_adjust(void) { }
+ #endif
*** a/src/backend/postmaster/pgarch.c
--- b/src/backend/postmaster/pgarch.c
***************
*** 170,175 **** pgarch_start(void)
--- 170,178 ----
  			/* Drop our connection to postmaster's shared memory, as well */
  			PGSharedMemoryDetach();
  
+ 			/* allow us to be killed on oom */
+ 			oom_adjust();
+ 
  			PgArchiverMain(0, NULL);
  			break;
  #endif
*** a/src/backend/postmaster/postmaster.c
--- b/src/backend/postmaster/postmaster.c
***************
*** 3076,3081 **** BackendStartup(Port *port)
--- 3076,3084 ----
  		/* Perform additional initialization and collect startup packet */
  		BackendInitialize(port);
  
+ 		/* allow us to be killed on oom */
+ 		oom_adjust();
+ 
  		/* And run the backend */
  		proc_exit(BackendRun(port));
  	}
*** a/src/include/postmaster/fork_process.h
--- b/src/include/postmaster/fork_process.h
***************
*** 13,17 ****
--- 13,18 ----
  #define FORK_PROCESS_H
  
  extern pid_t fork_process(void);
+ extern void oom_adjust(void);
  
  #endif   /* FORK_PROCESS_H */