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memstat is a small proc-based utility designed to help the system administrator figure out what's consuming memory. Like ps, it lists all the processes, and how much private memory each is using. Unlike ps, it also lists all the shared objects (shared libraries and executables) that are in memory, and which processes are using those shared objects. Here's a brief tutorial:
Suppose you do a ps, and you see this:
root 117 0.0 0.0 812 0 3 SW Sep 7 0:00 getty
root 118 0.0 0.0 812 0 4 SW Sep 7 0:00 getty
root 119 0.0 0.0 812 0 5 SW Sep 7 0:00 getty
root 120 0.0 0.0 812 0 6 SW Sep 7 0:00 getty
root 5810 0.0 0.0 812 0 1 SW 18:03 0:00 getty
And you think to yourself, 812k for each copy of getty? That seems excessive! So, you generate a memstat listing, to figure out why it takes 812k to implement getty. The listing looks like this:
224k: PID 1 (/sbin/telinit)
216k: PID 9 (/sbin/update)
224k: PID 20 (/sbin/kerneld)
228k: PID 74 (/sbin/syslogd)
408k: PID 76 (/sbin/klogd)
232k: PID 82 (/usr/sbin/rpc.portmap)
224k: PID 84 (/usr/sbin/inetd)
344k: PID 87 (/usr/sbin/diald)
256k: PID 91 (/usr/sbin/diald)
236k: PID 109 (/usr/sbin/cron)
224k: PID 117 (/sbin/getty)
224k: PID 118 (/sbin/getty)
224k: PID 119 (/sbin/getty)
224k: PID 120 (/sbin/getty)
220k: PID 121 (/usr/local/sbin/hayes)
496k: PID 4595 (/usr/bin/tcsh)
224k: PID 5810 (/sbin/getty)
336k: PID 5856 (/bin/sh)
2380k: PID 5872 (/usr/X11R6/bin/XF86_SVGA)
276k: PID 5876 (/usr/X11R6/bin/fvwm)
2016k: PID 5984 (/usr/local/lib/netscape/netscape)
432k: PID 6129 (/usr/local/bin/rxvt)
460k: PID 6130 (/usr/bin/tcsh)
240k: PID 6164 (unknown)
460k: PID 6165 (/usr/bin/tcsh)
24k: /lib/ld-linux.so.1 1 9 20 74 76 82 84 87 91 109 117 118 119 120 1...
8k: /lib/libdl.so 5856 5872 5984
540k: /usr/lib/libc.so 1 9 20 74 76 82 84 87 91 109 117 118 119 120 121...
32k: /usr/lib/libm.so 5872
128k: /lib/libreadline.so.2.0 5856
224k: /usr/lib/libcurses.so 4595 5856 6130 6165
4k: /usr/local/sbin/hayes 121
52k: /usr/local/bin/rxvt 6129
8k: unknown 6164
48k: /usr/X11R6/lib/libXpm.so 5876 5984
72k: /usr/X11R6/lib/libICE.so 5984 6129
32k: /usr/X11R6/lib/libSM.so 5984 6129
628k: /usr/X11R6/lib/libX11.so 5876 5984 6129
40k: /usr/X11R6/lib/libXext.so 5876 5984
64k: /usr/X11R6/lib/libXmu.so 5984
260k: /usr/X11R6/lib/libXt.so 5984
308k: /bin/sh 5856
252k: /usr/bin/tcsh 4595 6130 6165
2608k: /usr/X11R6/bin/XF86_SVGA 5872
112k: /usr/X11R6/bin/fvwm 5876
12k: /sbin/kerneld 20
24k: /sbin/syslogd 74
20k: /sbin/klogd 76
20k: /sbin/telinit 1
4k: /sbin/update 9
12k: /sbin/getty 117 118 119 120 5810
24k: /usr/sbin/cron 109
68k: /usr/sbin/diald 87 91
16k: /usr/sbin/inetd 84
24k: /usr/sbin/rpc.portmap 82
4392k: /usr/local/lib/netscape/netscape 5984
--------
21088k
The first thing you see is these lines, which indicate that each copy of getty has allocated 224k of private data. Each getty is using a separate 224k.
224k: PID 117 (/sbin/getty)
224k: PID 118 (/sbin/getty)
224k: PID 119 (/sbin/getty)
224k: PID 120 (/sbin/getty)
224k: PID 5810 (/sbin/getty)
The next thing you see is this line, which indicates that 16k is being used to hold the getty executable itself. The executable is shared among processes 117, 118, 119, 120, and 5810 (all the gettys).
16k: /sbin/getty 117 118 119 120 5810
To explain the 812k figure, you also have to look at these lines, which show that the standard C library is taking up 544k, and that the shared-library loader is taking up 28k. These two objects are being used by almost all the processes, including all the gettys:
544k: /usr/lib/libc.so 1 9 20 74 76 82 84 87 91 109 117 118 119 120 121...
28k: /lib/ld-linux.so.1 1 9 20 74 76 82 84 87 91 109 117 118 119 120 1...
If you add up 16k + 224k + 544k + 28k, you get 812k.
memstat is currently available in source-code form on my web-page.
http://charm.cs.uiuc.edu/~jyelon/software.html
- Josh
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