I have a number of machines which I have to administer, all of which are
currently running a base of RedHat Linux 7.2 which a run a mixture of 2.4.20
kernels compiled on the machine from the source, or RedHats latest 2.4.18 ot
2.4.20 rpms, all of them have varying harward (from Dell PowerEdge 1650's,
to hand build systems based around SiS's Chipsets) all of which exhibit
symptoms which I beleive could be a kernel memory leak.
As an example, I have a system which has 256Mb of Ram running a
compiled-from-source 2.4.20 kernel, and normally runs apache httpd, tomcat,
and postgres. After 2 months of running I shut down all applications and the
output of free showed 200Mb+ in use, 20MB in swap, and approx 5Mb in
buffers. After rebooting the machine and restarting all the apps it showed
80Mb used, 0MB swap, 5MB of buffers, which seemed odd.
As a second example I have a Poweredge 350 which does little more than using
ip tables as a firewall and runs snort and ssh, which after 127 days of
uptime the free output looks like this;
total used free shared buffers cached
Mem: 126104 123748 2356 0 16028 86604
-/+ buffers/cache: 21116 104988
Swap: 265064 2780 262284
and ps -vax looks like this;
PID TTY STAT TIME MAJFL TRS DRS RSS %MEM COMMAND
1 ? S 0:06 122 23 1392 460 0.3 init [3]
2 ? SW 0:00 0 0 0 0 0.0 [keventd]
3 ? SW 0:00 0 0 0 0 0.0 [kapmd]
4 ? SWN 0:00 0 0 0 0 0.0 [ksoftirqd_CPU0]
5 ? SW 0:18 0 0 0 0 0.0 [kswapd]
6 ? SW 0:00 0 0 0 0 0.0 [bdflush]
7 ? SW 0:00 0 0 0 0 0.0 [kupdated]
8 ? SW 0:00 0 0 0 0 0.0 [mdrecoveryd]
12 ? SW 1:52 0 0 0 0 0.0 [kjournald]
87 ? SW 0:00 0 0 0 0 0.0 [khubd]
678 ? S 0:48 117 23 1452 568 0.4 syslogd -m 0
683 ? S 0:32 38 18 2021 496 0.3 klogd -2
795 ? S 0:00 23 13 1386 456 0.3 /usr/sbin/apmd -p
10 -w
828 ? S 0:05 57 18 1573 596 0.4 crond
847 ? S 0:00 17 12 1435 480 0.3 /usr/sbin/atd
854 ? S 1:46 31 714 1729 784 0.6 /usr/local/sbin/sshd
860 ? SL 0:02 336 174 1637 1804 1.4 /usr/local/bin/ntpd
865 tty1 S 0:00 104 6 1381 372 0.2 /sbin/mingetty tty1
866 tty2 S 0:00 104 6 1381 372 0.2 /sbin/mingetty tty2
867 tty3 S 0:00 104 6 1381 372 0.2 /sbin/mingetty tty3
868 tty4 S 0:00 104 6 1381 372 0.2 /sbin/mingetty tty4
869 tty5 S 0:00 104 6 1381 372 0.2 /sbin/mingetty tty5
870 tty6 S 0:00 104 6 1381 372 0.2 /sbin/mingetty tty6
2284 ? S 52:47 504 313 9678 8016 6.3
/usr/local/bin/snort -c
15194 ? S 0:00 10 460 2947 1108 0.8 sendmail: accepting
conn
21933 ? S 0:00 166 714 5209 1520 1.2 /usr/local/sbin/sshd
21935 ? S 0:00 53 714 5225 1740 1.3 /usr/local/sbin/sshd
21936 pts/0 S 0:00 275 484 2027 1328 1.0 -bash
21976 pts/0 S 0:00 257 673 1786 1168 0.9 ssh
another.machine.name
22514 ? S 0:00 166 714 5209 1520 1.2 /usr/local/sbin/sshd
22516 ? S 0:00 53 714 5225 1732 1.3 /usr/local/sbin/sshd
22517 pts/1 S 0:00 276 484 2063 1368 1.0 -bash
22635 ? S 0:00 166 714 5209 1520 1.2 /usr/local/sbin/sshd
22637 ? S 0:00 53 714 5225 1732 1.3 /usr/local/sbin/sshd
22638 pts/2 S 0:00 276 484 2063 1368 1.0 -bash
22686 pts/2 R 0:00 161 59 2572 684 0.5 ps -vax
which, when you add up the memory output from ps -vax does not appear to
tally with the memory usage reported by free.
Out of the 20ish machines I'm running on the various kernels all seem to
exhibit the behaviour of increasing memory usage over time that can not be
cured by shutting down the applications on the system.
Does anyone have any hints/pointers as to how I can investigate this further
to see what may be causing the problem?
Thanks,
Al.
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