On Fri, May 18, 2012 at 10:39 AM, Les Mikesell <lesmikesell@xxxxxxxxx>wrote:
> On Fri, May 18, 2012 at 11:24 AM, Michael Coffman
> <michael.coffman@xxxxxxxxxxxxx> 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@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@xxxxxxxxx
> _______________________________________________
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> CentOS@xxxxxxxxxx
> http://lists.centos.org/mailman/listinfo/centos
>
--
-MichaelC
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