On Fri, May 18, 2012 at 10:39 AM, Les Mikesell <lesmikesell at gmail.com>wrote: > On Fri, May 18, 2012 at 11:24 AM, Michael Coffman > <michael.coffman at avagotech.com> wrote: > > > >> If you are already overcommitted, what do you expect to happen when > >> you say not to allow that? The kernel doesn't have a really good way > >> to handle that situation (or any other OOM condition for that > >> matter...). > >> > >> > > OK. So I was confused because free shows I have plenty of memory and I > am > > only now noticing that Committed_AS shows a very large value. This is > > largely an idle system: > > > > total used free shared buffers cached > > Mem: 2052176 951648 1100528 0 147580 626096 > > -/+ buffers/cache: 177972 1874204 > > Swap: 2052088 0 2052088 > > > > So my real question should have been why would the Committed_AS value be > so > > large? > > Committed_AS: 137197248820 kB > > > > On the exact same hardware with fresh build of centos5u4 and overcommit > > turned on: > > Committed_AS: 125716 kB > > I think that means an application has malloc()'d but not actually used > a huge amount of memory. It used to be a common practice to test the > amount of memory available by requesting more until the request > failed, so it could be meaningless. If overcommit is turned off the > app gets an error when it expects and backs off. The Committed_AS is > an estimate of how much RAM/swap you would be likely to need if the > requested storage is actually used. > > I get how overcommit works and it's affect on malloc. I intentionally turn it off so malloc will return a correct value when a process can't get enough memory. What I currently don't understand is the large value of Committed_AS on my centos6/rhel6 systems. I just did a fresh build of centos6u2 and there is very little running and the value is: Committed_AS: 136382202700 kB There is almost nothing running.... Filtering out kernel processes here is the list of running processes $ps -e -o uid,pid,ppid,rsz,vsz,cmd |grep -v \\[ UID PID PPID RSZ VSZ CMD 0 1 0 1608 23636 /sbin/init 0 493 1 1156 11112 /sbin/udevd -d 0 1072 493 1168 11108 /sbin/udevd -d 0 1073 493 1164 11108 /sbin/udevd -d 0 1147 1 828 27688 auditd 0 1172 1 1472 252980 /sbin/rsyslogd -i /var/run/syslogd.pid -c 4 32 1215 1 1004 19084 rpcbind 29 1233 1 1212 25292 rpc.statd 81 1269 1 940 25676 dbus-daemon --system 70 1281 1280 524 31952 avahi-daemon: chroot helper 0 1291 1 3420 92432 cupsd -C /etc/cups/cupsd.conf 0 1316 1 624 4132 /usr/sbin/acpid 68 1325 1 4272 29572 hald 0 1326 1325 1336 18156 hald-runner 0 1365 1326 1268 20272 hald-addon-input: Listening on /dev/input/event3 /dev/input/event0 /dev/input/event1 68 1369 1326 1164 17856 hald-addon-acpi: listening on acpid socket /var/run/acpid.socket 0 1389 1 1428 120820 /usr/sbin/ypbind 0 1439 1 280 10524 rpc.rquotad 0 1455 1 808 21464 rpc.mountd 0 1472 1 520 6300 /usr/sbin/mcelog --daemon 0 1492 1 1216 64068 /usr/sbin/sshd 0 1500 1 1088 24236 xinetd -stayalive -pidfile /var/run/xinetd.pid 38 1508 1 1740 34448 ntpd -u ntp:ntp -p /var/run/ntpd.pid -g 0 1516 1 368 8356 rpc.rstatd 0 1525 1 6220 57364 /usr/sbin/amd -F /etc/amd.conf 0 1608 1 3304 80768 /usr/libexec/postfix/master 0 1629 1 884 9216 abrt-dump-oops -d /var/spool/abrt -rwx /var/log/messages 0 1638 1 1304 22000 /usr/sbin/abrtd 0 1646 1 1236 20416 crond 0 2032 1 468 21492 /usr/sbin/atd 0 2292 1 4564 100224 /usr/sbin/snmpd -LS 4 d -Lf /dev/null -p /var/run/snmpd.pid -a 89 2305 1608 3260 80848 pickup -l -t fifo -u 89 2306 1608 3304 80916 qmgr -l -t fifo -u 99 2425 1 4052 136382123488 /opt/ictools/64bit/synopsys-aserver/bin/AServer 0 2433 1 580 4116 /sbin/mingetty /dev/tty1 0 2435 1 584 4116 /sbin/mingetty /dev/tty2 0 2437 1 580 4116 /sbin/mingetty /dev/tty3 0 2439 1 580 4116 /sbin/mingetty /dev/tty4 0 2441 1 580 4116 /sbin/mingetty /dev/tty5 0 2443 1 580 4116 /sbin/mingetty /dev/tty6 0 3001 1492 3888 99900 sshd: rootm at pts/0 0 3004 3001 3692 13320 -bash 0 3277 3004 920 11316 ps -e -o uid,pid,ppid,rsz,vsz,cmd > -- > Les Mikesell > lesmikesell at gmail.com > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos > -- -MichaelC