Re: [RFC PATCH v2 1/3] misc_cgroup: add support for nofile limit

Thanks for your time.

Tejun Heo wrote on 2021/7/27 5:27:

On Thu, Jul 22, 2021 at 11:20:17PM +0800, brookxu wrote:

quoted

From: Chunguang Xu <redacted>

Since the global open files are limited, in order to avoid the
abnormal behavior of some containers from generating too many
files, causing other containers to be unavailable, we need to
limit the open files of some containers.

v2: fix compile error while CONFIG_CGROUP_MISC not set.

Signed-off-by: Chunguang Xu <redacted>
Reported-by: kernel test robot <redacted>

This is different from pid in that there's no actual limit on how many open
files there can be in the system other than the total amount of available
memory. I don't see why this would need a separate limit outside of memory
control. A couple machines I looked at all have file-max at LONG_MAX by
default too.

According to files_maxfiles_init(), we only allow about 10% of free memory to
create filps, and each filp occupies about 1K of cache. In this way, on a 16G
memory machine, the maximum usable filp is about 1,604,644. In general
scenarios, this may not be a big problem, but if the task is abnormal, it will
very likely become a bottleneck and affect other modules. 

Thanks.