[systemd-devel] systemd-cgls - Memory overflow

[Sven Anders]

Hello!

I'm experiencing a problem with systemd-cgls while testing systemd.

I run systemd for tests on a small KVM VM with ~700MB RAM and no swap.

If I execute the "systemd-cgls" command, I see the tree but without
the command lines of the executables. I only see "n/a".

Example:

└ system
  ├ 1 n/a
  ├ sshd.service
  │ ├ 608 n/a
  │ ├ 639 n/a
  │ ├ 641 n/a
  │ ├ 671 n/a
  │ └ 672 n/a
  ├ getty at .service
  │ ├ tty1
  │ │ ├ 302 n/a
  │ │ └ 610 n/a
  │ └ tty2
  │   └ 301 n/a
  ├ webredirect.service
  │ └ 300 n/a
  ├ confgui.service
  │ └ 299 n/a
  ├ dbus.service
  │ └ 340 n/a
  ├ systemd-logind.service
  │ └ 294 n/a
  ├ systemd-journald.service
  │ └ 174 n/a
  └ udev.service
    ├ 171 n/a
    ├ 348 n/a
    └ 349 n/a

I investigated this further with strace and get the following errors:

[...]
access("/sys/fs/cgroup/systemd/system/webredirect.service", F_OK) = 0
open("/sys/fs/cgroup/systemd/system/webredirect.service/cgroup.procs", O_RDONLY|O_LARGEFILE|O_CLO
EXEC) = 6
fstat64(6, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x40047000
read(6, "300\n", 4096)                  = 4
open("/proc/300/cmdline", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 7
fstat64(7, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x40048000
read(7, "/usr/sbin/webredirect\0-f\0", 1024) = 25
close(7)                                = 0
munmap(0x40048000, 4096)                = 0
read(6, "", 4096)                       = 0
open("/proc/300/cmdline", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 7
mmap2(NULL, 1075859456, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = -1 ENOMEM (Cann
ot allocate memory)
mmap2(NULL, 1075859456, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = -1 ENOMEM (Cann
ot allocate memory)
brk(0x81ff6000)                         = 0x41de2000
mmap2(NULL, 1075990528, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = -1 ENOMEM (Cann
ot allocate memory)
close(7)
[...]

The command line is read successfully, but it's opened a second time and this time the
tool tries to memory map 1.075.859.456 bytes. Why? I think it will work, if I add swap space
or provide more RAM. But the tool should work with small RAM too...


Regards
 Sven Anders

-- 
 Sven Anders <anders at anduras.de>                 () UTF-8 Ribbon Campaign
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