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Commit93f4d7f

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Support Linux's oom_score_adj API as well as the older oom_adj API.
The simplest way to handle this is just to copy-and-paste the relevantcode block in fork_process.c, so that's what I did. (It's possible thatsomething more complicated would be useful to packagers who want to workwith either the old or the new API; but at this point the number of suchpeople is rapidly approaching zero, so let's just get the minimal thingdone.) Update relevant documentation as well.
1 parentb9212e3 commit93f4d7f

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3 files changed

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‎contrib/start-scripts/linux

Lines changed: 10 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -42,10 +42,14 @@ PGLOG="$PGDATA/serverlog"
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# It's often a good idea to protect the postmaster from being killed by the
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# OOM killer (which will tend to preferentially kill the postmaster because
45-
# of the way it accounts for shared memory). Setting the OOM_ADJ value to
46-
# -17 will disable OOM kill altogether. If you enable this, you probably want
47-
# to compile PostgreSQL with "-DLINUX_OOM_ADJ=0", so that individual backends
48-
# can still be killed by the OOM killer.
45+
# of the way it accounts for shared memory). Setting the OOM_SCORE_ADJ value
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# to -1000 will disable OOM kill altogether. If you enable this, you probably
47+
# want to compile PostgreSQL with "-DLINUX_OOM_SCORE_ADJ=0", so that
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# individual backends can still be killed by the OOM killer.
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#OOM_SCORE_ADJ=-1000
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# Older Linux kernels may not have /proc/self/oom_score_adj, but instead
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# /proc/self/oom_adj, which works similarly except the disable value is -17.
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# For such a system, enable this and compile with "-DLINUX_OOM_ADJ=0".
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#OOM_ADJ=-17
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## STOP EDITING HERE
@@ -78,6 +82,7 @@ test -x $DAEMON ||
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case$1in
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start)
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echo -n"Starting PostgreSQL:"
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test x"$OOM_SCORE_ADJ"!= x&&echo"$OOM_SCORE_ADJ"> /proc/self/oom_score_adj
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test x"$OOM_ADJ"!= x&&echo"$OOM_ADJ"> /proc/self/oom_adj
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su -$PGUSER -c"$DAEMON -D '$PGDATA' &">>$PGLOG2>&1
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echo"ok"
@@ -90,6 +95,7 @@ case $1 in
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restart)
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echo -n"Restarting PostgreSQL:"
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su -$PGUSER -c"$PGCTL stop -D '$PGDATA' -s -m fast -w"
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test x"$OOM_SCORE_ADJ"!= x&&echo"$OOM_SCORE_ADJ"> /proc/self/oom_score_adj
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test x"$OOM_ADJ"!= x&&echo"$OOM_ADJ"> /proc/self/oom_adj
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su -$PGUSER -c"$DAEMON -D '$PGDATA' &">>$PGLOG2>&1
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echo"ok"

‎doc/src/sgml/runtime.sgml

Lines changed: 16 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -1268,7 +1268,7 @@ default:\
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In Linux 2.4 and later, the default virtual memory behavior is not
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optimal for <productname>PostgreSQL</productname>. Because of the
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way that the kernel implements memory overcommit, the kernel might
1271-
terminate the <productname>PostgreSQL</productname>server (the
1271+
terminate the <productname>PostgreSQL</productname>postmaster (the
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master server process) if the memory demands of
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another process cause the system to run out of virtual memory.
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</para>
@@ -1317,22 +1317,31 @@ sysctl -w vm.overcommit_memory=2
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<para>
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Another approach, which can be used with or without altering
13191319
<varname>vm.overcommit_memory</>, is to set the process-specific
1320-
<varname>oom_adj</> value for the postmaster process to <literal>-17</>,
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thereby guaranteeing it will not be targeted by the OOM killer. The
1322-
simplest way to do this is to execute
1320+
<varname>oom_score_adj</> value for the postmaster process to
1321+
<literal>-1000</>,thereby guaranteeing it will not be targeted by the OOM
1322+
killer. Thesimplest way to do this is to execute
13231323
<programlisting>
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echo -17 > /proc/self/oom_adj
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echo -1000 > /proc/self/oom_score_adj
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</programlisting>
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in the postmaster's startup script just before invoking the postmaster.
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Note that this action must be done as root, or it will have no effect;
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so a root-owned startup script is the easiest place to do it. If you
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do this, you may also wish to build <productname>PostgreSQL</>
1330-
with <literal>-DLINUX_OOM_ADJ=0</> added to <varname>CPPFLAGS</>.
1330+
with <literal>-DLINUX_OOM_SCORE_ADJ=0</> added to <varname>CPPFLAGS</>.
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That will cause postmaster child processes to run with the normal
1332-
<varname>oom_adj</> value of zero, so that the OOM killer can still
1332+
<varname>oom_score_adj</> value of zero, so that the OOM killer can still
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target them at need.
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</para>
13351335

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<para>
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Older Linux kernels do not offer <filename>/proc/self/oom_score_adj</>,
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but may have a previous version of the same functionality called
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<filename>/proc/self/oom_adj</>. This works the same except the disable
1340+
value is <literal>-17</> not <literal>-1000</>. The corresponding
1341+
build flag for <productname>PostgreSQL</> is
1342+
<literal>-DLINUX_OOM_ADJ=0</>.
1343+
</para>
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13361345
<note>
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<para>
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Some vendors' Linux 2.4 kernels are reported to have early versions

‎src/backend/postmaster/fork_process.c

Lines changed: 33 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -68,12 +68,40 @@ fork_process(void)
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* process sizes *including shared memory*. (This is unbelievably
6969
* stupid, but the kernel hackers seem uninterested in improving it.)
7070
* Therefore it's often a good idea to protect the postmaster by
71-
* setting itsoom_adj value negative (which has to be done in a
72-
* root-owned startup script).If you just do that much, all child
71+
* setting itsoom_score_adj value negative (which has to be done in a
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* root-owned startup script).If you just do that much, all child
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* processes will also be protected against OOM kill, which might not
74-
* be desirable. You can then choose to build with LINUX_OOM_ADJ
75-
* #defined to 0, or some other value that you want child processes to
76-
* adopt here.
74+
* be desirable. You can then choose to build with
75+
* LINUX_OOM_SCORE_ADJ #defined to 0, or to some other value that you
76+
* want child processes to adopt here.
77+
*/
78+
#ifdefLINUX_OOM_SCORE_ADJ
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{
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/*
81+
* Use open() not stdio, to ensure we control the open flags. Some
82+
* Linux security environments reject anything but O_WRONLY.
83+
*/
84+
intfd=open("/proc/self/oom_score_adj",O_WRONLY,0);
85+
86+
/* We ignore all errors */
87+
if (fd >=0)
88+
{
89+
charbuf[16];
90+
intrc;
91+
92+
snprintf(buf,sizeof(buf),"%d\n",LINUX_OOM_SCORE_ADJ);
93+
rc=write(fd,buf,strlen(buf));
94+
(void)rc;
95+
close(fd);
96+
}
97+
}
98+
#endif/* LINUX_OOM_SCORE_ADJ */
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100+
/*
101+
* Older Linux kernels have oom_adj not oom_score_adj. This works
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* similarly except with a different scale of adjustment values.
103+
* If it's necessary to build Postgres to work with either API,
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* you can define both LINUX_OOM_SCORE_ADJ and LINUX_OOM_ADJ.
77105
*/
78106
#ifdefLINUX_OOM_ADJ
79107
{

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