Severe Linux 2.4 kernel memory leakage

From: Chris Chabot (chabotc@reviewboard.com)
Date: Sun Nov 25 2001 - 09:49:27 EST


Hi, I have a firewall / file server box which is displaying (severe)
memory leakage, presumably by the kernel.

The box has ran Redhat 7.1 and 7.2, with plain vanilla linux kernels
2.4.9 upto 2.4.15, in all situations the same problem appeared.

The problem is that when the box boots up, it uses about 60Mb of memory.
However after only 1 1/2 days, the memory usage is already around 430Mb
(!!). (this is ofcource used - buffers - cache, as displayed by 'free').

When i do a ps aux, and add the 'resident' memory usage of the
applications, the memory usage should be around 70-80Mb (a bit higher
then @ boot time since bind uses more memory for caching). Yet 'free'
happely tells me:

             total used free shared buffers
cached
Mem: 1029752 1019188 10564 0 130888
456000
-/+ buffers/cache: 432300 597452
Swap: 2104464 996 2103468

When the box keeps on running for about a month, the memory usage gets
so high that it turns into a swap-crazy, low-memory and slow server ;-/
(it does free up cache memory, and swaps stuff out, however the 'leaked'
memory only grows and is never re-claimed).

The box runs dhcpd, bind, fetchmail (cron), pppd (to adsl modem), smb,
nfs, xinetd (imapd mostly) and sshd.

Also it has a (custom) iptables firewall script, and a simple ip route
hack to allow 'outbound interface == inbound interface' (using ipmark
based routing) for my cable modem & adsl modem. Also it has a 310Gb raid
0 array on 4 IDE disks.

Since this box has ran several versions of different kernels, redhat
distro's, and various firewall scripts. I tend to believe this is a more
'structural' problem within the linux kernel.

The box firewalls for both my cable modem and my adsl modem, and has 3
network cards (1 direct to cable, one direct to adsl, one to local
network).

The hardware on the box is : Asus p2b-ds, 2x p3-600, 1Gb (ECC) ram, 3
network cards (1x Intel EtherExpressPro, 2x 3c905 tx), Internal adaptect
29xx u2w scsi, internal intel IDE, 2x Seagate Cheetah (u2w) 18 Gb disks
(/ and /var), 4x 80 Gb Maxtor IDE disks (raid 0 array) and a NVidia TNT2
card. This hardware

The kernel is compiled with all network- and scsi card and raid0 drivers
build in, and nfs + iptables as modules. The machine currently uses ext3
(also build in), however this problem was also present before i
converted the raid0 volume to ext3, so i do not suspect it to cause this
problem. The kernel is also set for HIGHMEM (4gb) to use the last Mb's
of the 1Gb of ram (else 127Mb isnt detected).

If there is any additional information i can provide, please feel free
to ask! Also please CC me in the replies, since i am not subscribed to
the linux-kernel list.

I do not know which component (iptables / route hack / raid0 / network
cards / highmem) cause this problem. I run several of these components
on other servers, without the same problems.. However in this
combination, the kernel seems very leaky ;-/ Any and all sugestions or
help is greatly apreciated.

Additional info on the box:

My Routes script (to allow cable and adsl to use the same outbound
interface as inbound, to prevent invalid routing over the default gw):

#!/bin/bash
echo 1 > /proc/sys/net/ipv4/route/flush
echo "Removing old rules"
ip rule del from 24.132.33.179 table a2000 &>/dev/null
ip rule del from 213.84.192.197 table xs4all &>/dev/null
ip route del table a2000 &>/dev/null
ip route del table xs4all &>/dev/null
echo "Setting routing"
ip rule add from 24.132.33.179 table a2000 prio 20
ip rule add from 213.84.192.197 table xs4all prio 30
ip route add 0/0 table a2000 dev eth0 prio 20
ip route add 0/0 table xs4all dev ppp0 prio 30

free (this is after 1 1/2 day):

             total used free shared buffers
cached
Mem: 1029752 1018528 11224 0 131608
454556
-/+ buffers/cache: 432364 597388
Swap: 2104464 996 2103468

ps aux:

USER PID %CPU %MEM VSZ RSS TTY STAT START TIME
COMMAND
root 1 0.0 0.0 1416 476 ? S Nov24 0:04 init
[3]
root 2 0.0 0.0 0 0 ? SW Nov24 0:00
[keventd]
root 3 0.0 0.0 0 0 ? SWN Nov24 0:00
[ksoftirqd_CPU0]
root 4 0.0 0.0 0 0 ? SWN Nov24 0:00
[ksoftirqd_CPU1]
root 5 0.0 0.0 0 0 ? SW Nov24 0:13
[kswapd]
root 6 0.0 0.0 0 0 ? SW Nov24 0:00
[bdflush]
root 7 0.0 0.0 0 0 ? SW Nov24 0:03
[kupdated]
root 8 0.0 0.0 0 0 ? SW Nov24 0:00
[scsi_eh_0]
root 9 0.0 0.0 0 0 ? SW< Nov24 0:00
[mdrecoveryd]
root 10 0.0 0.0 0 0 ? SW Nov24 0:01
[kjournald]
root 145 0.0 0.0 0 0 ? SW Nov24 0:00
[kjournald]
root 146 0.0 0.0 0 0 ? SW Nov24 0:01
[kjournald]
root 147 0.0 0.0 0 0 ? SW Nov24 0:18
[kjournald]
root 719 0.0 0.0 1476 604 ? S Nov24 0:00 syslogd
-m 0 -r
root 724 0.0 0.0 1404 476 ? S Nov24 0:00 klogd -2
-x
bin 744 0.0 0.0 1660 764 ? S Nov24 0:00
portmap
root 801 0.0 0.0 1792 568 ? S Nov24 0:00
rpc.rquotad
root 806 0.0 0.0 1620 716 ? S Nov24 0:00
rpc.mountd
root 811 0.0 0.0 0 0 ? SW Nov24 0:20
[nfsd]
root 812 0.0 0.0 0 0 ? SW Nov24 0:20
[nfsd]
root 813 0.0 0.0 0 0 ? SW Nov24 0:20
[nfsd]
root 814 0.0 0.0 0 0 ? SW Nov24 0:19
[nfsd]
root 815 0.0 0.0 0 0 ? SW Nov24 0:20
[nfsd]
root 816 0.0 0.0 0 0 ? SW Nov24 0:19
[nfsd]
root 817 0.0 0.0 0 0 ? SW Nov24 0:20
[nfsd]
root 818 0.0 0.0 0 0 ? SW Nov24 0:20
[nfsd]
root 819 0.0 0.0 0 0 ? SW Nov24 0:00
[lockd]
root 820 0.0 0.0 0 0 ? SW Nov24 0:00
[rpciod]
root 892 0.0 0.0 1920 896 ? S Nov24 0:00
/usr/sbin/pppd ca
root 911 0.0 0.1 2680 1084 ? S Nov24 0:02
/usr/sbin/sshd
root 931 0.0 0.1 2312 1032 ? S Nov24 0:00 xinetd
-stayalive
root 951 0.0 0.0 1796 648 ? S Nov24 0:00
/usr/sbin/dhcpd
named 1009 0.0 0.4 15328 4364 ? S Nov24 0:00 named -u
named
named 1011 0.0 0.4 15328 4364 ? S Nov24 0:01 named -u
named
named 1012 0.0 0.4 15328 4364 ? S Nov24 0:07 named -u
named
named 1013 0.0 0.4 15328 4364 ? S Nov24 0:06 named -u
named
named 1014 0.0 0.4 15328 4364 ? S Nov24 0:04 named -u
named
named 1015 0.0 0.4 15328 4364 ? S Nov24 0:01 named -u
named
root 1033 0.9 0.0 1456 528 ? S Nov24 29:38
/usr/sbin/pptp pp
root 1043 0.0 0.1 5684 1384 ? S Nov24 0:10 sendmail:
accepti
root 1062 0.0 0.0 1648 676 ? S Nov24 0:00
crond
root 1541 0.0 0.0 1388 380 tty1 S Nov24 0:00
/sbin/mingetty tt
root 1542 0.0 0.0 1388 380 tty2 S Nov24 0:00
/sbin/mingetty tt
root 1545 0.0 0.0 1448 560 ? S Nov24 0:00
/usr/sbin/pptp pp
root 7003 0.0 0.1 3260 1132 ? S 05:00 0:00 smbd
-D
root 7008 0.0 0.1 2448 1128 ? S 05:00 0:00 nmbd
-D
root 7609 0.0 0.1 3732 2016 ? S 14:39 0:00
/usr/sbin/sshd
root 7611 0.0 0.1 2612 1448 pts/1 S 14:39 0:00
-bash
root 13333 0.0 0.0 2656 752 pts/1 R 14:57 0:00 ps aux

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This archive was generated by hypermail 2b29 : Fri Nov 30 2001 - 21:00:19 EST