Re: [PATCH 0/2] proc: use subset option to hide some top-level procfs entries

[Alexey Gladkov <gladkov.alexey@gmail.com>]

On Thu, Jun 04, 2020 at 11:32:20PM +0200, Christian Brauner wrote:
> > Is it desirable to have meminfo and cpuinfo as they are today or do
> > people want them to reflect the ``container'' context.   So that
> > applications like the JVM don't allocation too many cpus or don't try
> > and consume too much memory, or run on nodes that cgroups current make
> > unavailable.
> > 
> > Are there any users or planned users of this functionality yet?
> > 
> > I am concerned that you might be adding functionality that no one will
> > ever use that will just add code to the kernel that no one cares about,
> > that will then accumulate bugs.  Having had to work through a few of
> > those cases to make each mount of proc have it's own super block I am
> > not a great fan of adding another one.
> > 
> > If the runc, lxc and other container runtime folks can productively use
> > such and option to do useful things and they are sensible things to do I
> > don't have any fundamental objection.  But I do want to be certain this
> > is a feature that is going to be used.
> 
> I'm not sure Alexey is introducing virtualized meminfo and cpuinfo (but
> I haven't had time to look at this patchset).

No. Not yet :) I just suggest a way to restrict access to files in the
procfs inside a container about which you know nothing.

> In any case, we are currently virtualizing:
> /proc/cpuinfo
> /proc/diskstats
> /proc/loadavg
> /proc/meminfo
> /proc/stat
> /proc/swaps
> /proc/uptime
> for each container with a tiny in-userspace filesystem LXCFS
> ( https://github.com/lxc/lxcfs )
> and have been doing that for years.

I know about it. The reason for the appearance of such a solution is also
clear.

> Having meminfo and cpuinfo virtualized in procfs was something we have
> been wanting for a long time and there have been patches by other people
> (from Siteground, I believe) to achieve this a few years back but were
> disregarded.
> 
> I think meminfo and cpuinfo would already be great. And if we're
> virtualizing cpuinfo we also need to virtualize the cpu bits exposed in
> /proc/stat. It would also be great to virtualize /proc/uptime. Right now
> we're achieving this essentially by substracting the time the init
> process of the pid namespace has started since system boot time, minus
> the time when the system started to get the actual reaper age (It's a
> bit more involved but that's the gist.).
> 
> This is all on the topic list for this year's virtual container's
> microconference at Plumber's and I would suggest we try to discuss the
> various requirements for something like this there. (I'm about to send
> the CFP out.)
> 
> Christian
> 

-- 
Rgrds, legion