Limit memory on a Docker container doesn't work

Question

I am running the last version of Docker on top of Ubuntu 13.04 (Raring Ringtail):

root@docker:~# docker version
Client version: 0.6.6
Go version (client         


        

Answer 1

free won't show it as this is enforced via cgroups. Instead on the host (outside the container) you can check using /sysfs and the cgroup memory:

vagrant@precise64:~$ docker run -m=524288 -d  -t busybox sleep 3600
f03a017b174f
vagrant@precise64:~$ cat /sys/fs/cgroup/memory/lxc/f03a017b174ff1022e0f46bc1b307658c2d96ffef1dd97e7c1929a4ca61ab80f//memory.limit_in_bytes
524288

To see it run out of memory, you can run something that will use more memory than you allocate - for example:

docker run -m=524288 -d -p 8000:8000 -t ubuntu:12.10  /usr/bin/python3 -m http.server
8480df1d2d5d
vagrant@precise64:~$ docker ps | grep 0f742445f839
vagrant@precise64:~$ docker ps -a | grep 0f742445f839
0f742445f839        ubuntu:12.10        /usr/bin/python3 -m    16 seconds ago       Exit 137                                blue_pig

In dmesg you should see the container and process killed:

[  583.447974] Pid: 1954, comm: python3 Tainted: GF          O 3.8.0-33-generic #48~precise1-Ubuntu
[  583.447980] Call Trace:
[  583.447998]  [] dump_header+0x83/0xbb
[  583.448108]  [] oom_kill_process.part.6+0x55/0x2cf
[  583.448124]  [] ? has_ns_capability_noaudit+0x15/0x20
[  583.448137]  [] ? mem_cgroup_iter+0x1b1/0x200
[  583.448150]  [] oom_kill_process+0x4d/0x50
[  583.448171]  [] mem_cgroup_out_of_memory+0x1f6/0x241
[  583.448187]  [] mem_cgroup_handle_oom+0x13f/0x24a
[  583.448200]  [] ? mem_cgroup_margin+0xad/0xb0
[  583.448212]  [] ? mem_cgroup_charge_common+0xa0/0xa0
[  583.448224]  [] mem_cgroup_do_charge+0x143/0x170
[  583.448236]  [] __mem_cgroup_try_charge+0x105/0x350
[  583.448249]  [] mem_cgroup_charge_common+0x57/0xa0
[  583.448261]  [] mem_cgroup_newpage_charge+0x2a/0x30
[  583.448275]  [] do_anonymous_page.isra.35+0xa3/0x2f0
[  583.448288]  [] handle_pte_fault+0x209/0x230
[  583.448301]  [] handle_mm_fault+0x2a0/0x3e0
[  583.448320]  [] __do_page_fault+0x1af/0x560
[  583.448341]  [] ? vfsub_read_u+0x30/0x40 [aufs]
[  583.448358]  [] ? aufs_read+0x107/0x140 [aufs]
[  583.448371]  [] ? vfs_read+0xb0/0x180
[  583.448384]  [] do_page_fault+0xe/0x10
[  583.448396]  [] page_fault+0x28/0x30
[  583.448405] Task in /lxc/0f742445f8397ee7928c56bcd5c05ac29dcc6747c6d1c3bdda80d8e688fae949 killed as a result of limit of /lxc/0f742445f8397ee7928c56bcd5c05ac29dcc6747c6d1c3bdda80d8e688fae949
[  583.448412] memory: usage 416kB, limit 512kB, failcnt 342