Monitor memory usage of child process

I have a Linux daemon that forks a few children and monitors them for crashes (restarting as needed). It will be great if the parent could monitor the memory usage of child processes - to detect memory leaks and restart child processes when the go beyond a certain size. How can I do this?

Solution

You should be able to get detailed memory information out of /proc/{PID}/status:

Name:   bash
State:  S (sleeping)
Tgid:   6053
Pid:    6053
PPid:   6050
TracerPid:  0
Uid:    1007    1007    1007    1007
Gid:    1007    1007    1007    1007
FDSize: 256
Groups: 1007 
VmPeak:    48076 kB
VmSize:    48044 kB
VmLck:         0 kB
VmHWM:      4932 kB
VmRSS:      2812 kB
VmData:     2232 kB
VmStk:        84 kB
VmExe:       832 kB
VmLib:      6468 kB
VmPTE:       108 kB
Threads:    1
SigQ:   0/8190
SigPnd: 0000000000000000
ShdPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 0000000000001010
SigCgt: 0000000188020001
CapInh: 0000000000000000
CapPrm: 0000000000000000
CapEff: 0000000000000000
Cpus_allowed:   0f
Mems_allowed:   00000000,00000001
voluntary_ctxt_switches:    69227121
nonvoluntary_ctxt_switches: 19071

However, unless memory leaks are dramatic, it's difficult to detect them looking at process statistics, because malloc and free are usually quite abstract from system calls (brk/sbrk) to which they correspond.

You can also check into /proc/${PID}/statm.