Re: [PATCH] aio: Add memcg accounting of user used data

On 06.12.2017 15:23, Michal Hocko wrote:

On Tue 05-12-17 13:00:54, Kirill Tkhai wrote:
[...]

quoted

This meets the problem in case of many containers
are used on the hardware node. Since aio_max_nr is
a global limit, any container may occupy the whole
available aio requests, and to deprive others the
possibility to use aio at all. The situation may
happen because of evil intentions of the container's
user or because of the program error, when the user
makes this occasionally

I am sorry to beat more on this but finally got around to
http://lkml.kernel.org/r/17b22d53-ad3d-1ba8-854f-fc2a43d86c44@virtuozzo.com
and read the above paragraph once again. I can see how accounting to
a memcg helps to reduce the memory footprint but I fail to see how it
helps the above scenario. Could you clarify wow you set up a limit to
prevent anybody from DoSing other containers by depleting aio_max_nr?

The memcg limit allows to increase aio_max_nr and the accounting guarantees
container can't exceed the limit. You may configure the limit and aio_max_nr
in the way, all containers requests in sum never reach aio_max_nr.

Kirill