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rsyslogd 4.6.4, compiled with:
    FEATURE_REGEXP:             Yes
    FEATURE_LARGEFILE:          No
    FEATURE_NETZIP (message compression):   Yes
    GSSAPI Kerberos 5 support:      Yes
    FEATURE_DEBUG (debug build, slow code): No
    Atomic operations supported:        Yes
    Runtime Instrumentation (slow code):    No

By adding a simple if-then filter in a custom conf file I notice quite a large jump in the memory used by rsyslogd.

Using the vanilla Debian conf file with no custom rules:

   VSZ   RSS %MEM
 51956  1400  0.0

By adding just a single if-then filter rsyslogd seems to double its memory consumption:

   VSZ   RSS %MEM
117492  1420  0.0

The typical filter:

if $programname contains 'sshd' and $syslogfacility-text == 'auth' then /var/log/ssh_auth.log

Using pmap to debug, the only process that shows a increase in memory is [ anon ].

[anon]                         24944 90480
/lib/ld-2.11.3.so                128   128
/lib/libc-2.11.3.so             3444  3444
/lib/libdl-2.11.3.so            2064  2064
/lib/libnsl-2.11.3.so           2136  2136
/lib/libnss_compat-2.11.3.so    2080  2080
/lib/libnss_files-2.11.3.so     2100  2100
/lib/libnss_nis-2.11.3.so       2092  2092
/lib/libpthread-2.11.3.so       2144  2144
/lib/librt-2.11.3.so            2080  2080
[stack]                           84    84
/usr/lib/libz.so.1.2.3.4        2140  2140
/usr/lib/rsyslog/imklog.so      2072  2072
/usr/lib/rsyslog/imuxsock.so    2060  2060
/usr/lib/rsyslog/lmnet.so       2068  2068
/usr/sbin/rsyslogd               320   320

Is there something wrong in my custom rule?

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1 Answer 1

up vote 3 down vote accepted

rsyslogd seems to have mapped some memory pages, but not actually used them. Your rsyslogd is taking whopping 0.0%, or 1.4 megabytes of your precious system memory. Your custom rule added 20 kilobytes to rsyslogd memory usage.

Virtual memory and Linux memory usage behaviour overall can be very confusing.

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1  
+1 This is virtual memory, not physical memory. Your OS can create enormous amounts of virtual memory effectively free. So there's no reason to care about it. –  David Schwartz Jun 5 '12 at 8:44
    
So, I was looking at the wrong place than! I'd better get a good linux memory howto next time. Thanks. –  ripat Jun 5 '12 at 11:21
1  
You said confusing? lwn.net/Articles/230975 –  ripat Jun 5 '12 at 11:42

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