Memory leak using agetty inside container


(Leo von Klenze) #1

Hi,

about 6 months before I had recognized that I have a memory leak on my servers running lxd infrastructure. First, the servers just run out of memory and I rebooted them. Until I had realized that this was a permanent issue it was too late to backtrack changes on the server to find the cause.
After a lot of research I had somehow found out that running agetty inside the container is causing the memory leak (slabinfo -r kmalloc-2k shows up huge calls of cgroup_mkdir).
I use Arch Linux as host and the archlinux image for my containers. This image is activating agetty sessions by default. I’ve also checked the ubuntu image but the ubuntu image does not launch agetty so there is no problem.
Since I’d deactivated agetty in the containers the memory leak is gone.

Unfortunately I’m not sure how to proceed in order to report this bug to the right channels. I’m even not sure if it is a agetty bug, a kernel bug or an lxc bug? Also, how to find the maintainer of the archlinux image to recommend him to deactivate agetty by default.

Any hints would be appreciated.

Thank you!


#2

uh, that’s strange. I have checked on my ubuntu servers (I only use Ubuntu) and I have still 2 Ubuntu 16.04 lxd containers and they are running agetty, and all my new ubuntu 18.04 containers run agetty.
I disabled it on a test 18.04 container with no side-effet that I could see so I don’t know why it’s enabled by default - a serial connection is not really that useful in a container.

For a laugh I installed archlinux in KVM and I noticed that the default kernel mem config is not exactly set like Ubuntu, that is, CONFIG_SLUB_MEMCG_SYSFS_ON is not set; I have absolutely no clue if it could matter, though.