Re: doc: Document Linux cgroup memory limits

Hi João

>> Attached v5 softens that sentence and recommends leaving a safety
>> margin below the limit, the same way the work_mem docs put it.

Thank you for updating a patch and adding information about cgroup might
be helpful.

Here are some comments.

I noticed some of the topics are already written in the above
'overcommit' section. For example, how to tune memory related parameters
and how postgres behaves after OOM killer terminates postgresql.
(I did small fix related to this topic in [1])

So I would do either of the followings:
1. Create a new section for cgroup as you did and only add some
references to overcommit section like "Please see the overcommit section
to decrease the risk of OOM by tuning memory parameters"

Or
2. Not create a new dedicated section for cgroup and just add "Note"
sub-section under the overcommit section, then write some peculiar
things for cgroup.

What do you think?

[1]
https://www.postgresql.org/message-id/ce269321-a7f4-48f4-a9ca-a4a4983b9fd6%40gmail.com

Regards,
Takeshi Ideriha