Setting oom_adj on linux?
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From: Tom Lane on 8 Jan 2010 09:27 Magnus Hagander <magnus(a)hagander.net> writes: > Do we need to make the value configurable? I'd certainly find it > interesting to set backends to say 5 or something like that, that > makes them less likely to be killed than any old "oops opened too big > file in an editor"-process, but still possible to kill if the system > is *really* running out of memory. I don't want to go to the trouble of creating (and documenting) a configure option for this. Much less a GUC ;-) What I suggest is that we do something like #ifdef LINUX_OOM_ADJ ... fprintf(oom, "%d\n", LINUX_OOM_ADJ); ... #endif Then, somebody who wants the feature would build with, say, -DLINUX_OOM_ADJ=0 or another value if they want that. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
From: Bruce Momjian on 8 Jan 2010 09:53 Alex Hunsaker wrote: > On Thu, Jan 7, 2010 at 20:26, Tom Lane <tgl(a)sss.pgh.pa.us> wrote: > > Alex Hunsaker <badalex(a)gmail.com> writes: > > > We can either drop this in core (with a lot of #ifdef LINUX added) > > Any thoughts on doing something like (in fork_process.c) > > #ifdef LINUX > void oom_adjust() > { > ... > } > #else > void oom_adjust() {} > #endif > > So there is only one #ifdef? It still leaves the ugly calls to the function... The usual solution for this kind of thing is: #ifdef LINUX #define OOM_ADJUST oom_adjust() #else #define OOM_ADJUST do {} while (0) #endif so there is no call or dummy function and you reference it in the code as: OOM_ADJUST; -- Bruce Momjian <bruce(a)momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + If your life is a hard drive, Christ can be your backup. + -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
From: Alex Hunsaker on 8 Jan 2010 10:24 On Fri, Jan 8, 2010 at 07:53, Bruce Momjian <bruce(a)momjian.us> wrote: > Alex Hunsaker wrote: >> On Thu, Jan 7, 2010 at 20:26, Tom Lane <tgl(a)sss.pgh.pa.us> wrote: >> > Alex Hunsaker <badalex(a)gmail.com> writes: > The usual solution for this kind of thing is: > > Â Â Â Â #ifdef LINUX > Â Â Â Â #define OOM_ADJUST oom_adjust() > Â Â Â Â #else > Â Â Â Â #define OOM_ADJUST do {} while (0) > Â Â Â Â #endif > > so there is no call or dummy function and you reference it in the code > as: Surely any compiler worth its salt would turn a call to an empty void function into a noop? Then again maybe I just hate macros :) -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
From: Alex Hunsaker on 8 Jan 2010 11:01 On Fri, Jan 8, 2010 at 07:27, Tom Lane <tgl(a)sss.pgh.pa.us> wrote: > Then, somebody who wants the feature would build with, say, > Â Â Â Â -DLINUX_OOM_ADJ=0 > or another value if they want that. Here is a stab at that. It sets oom_adj for: autovacuum workers archivers (pgarch.c) regular backends Also it updates the contrib linux starup script to start under an oom_adj of -17 Comments? *** 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 */
From: Tom Lane on 8 Jan 2010 11:37
Alex Hunsaker <badalex(a)gmail.com> writes: > On Fri, Jan 8, 2010 at 07:27, Tom Lane <tgl(a)sss.pgh.pa.us> wrote: >> Then, somebody who wants the feature would build with, say, >> -DLINUX_OOM_ADJ=0 >> or another value if they want that. > Here is a stab at that. Anybody have an objection to this basic approach? I'm in a bit of a hurry to get something like this into the Fedora RPMs, so barring objections I'm going to review this, commit it into HEAD, and then make a back-ported patch I can use with 8.4 in Fedora. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers |