Re: [Devel] Re: [RFC][PATCH 7/7] UBC: proc interface

From: Kir Kolyshkin
Date: Thu Aug 17 2006 - 12:11:46 EST

Greg KH wrote:
On Thu, Aug 17, 2006 at 05:43:16PM +0400, Kirill Korotaev wrote:
On Wed, Aug 16, 2006 at 07:44:30PM +0400, Kirill Korotaev wrote:

Add proc interface (/proc/user_beancounters) allowing to see current
state (usage/limits/fails for each UB). Implemented via seq files.
Ugh, why /proc? This doesn't have anything to do with processes, just
users, right? What's wrong with /sys/kernel/ instead?
We can move it, if there are much objections.

I am objecting. /proc is for processes so do not add any new files
there that do not deal with processes.

Or /sys/kernel/debug/user_beancounters/ in debugfs as this is just a
debugging thing, right?
debugfs is usually OFF imho.

No, distros enable it.

you don't export meminfo information in debugfs, correct?

That is because the meminfo is tied to processes, or was added to proc
before debugfs came about.

Then how about just /sys/kernel/ instead and use sysfs? Just remember,
one value per file please.
I see two problems with that. But let me first describe the current /proc/user_beancounters. This is how it looks like from inside a container:

# cat /proc/user_beancounters
Version: 2.5
uid resource held maxheld barrier limit failcnt
123: kmemsize 836919 1005343 2752512 2936012 0
lockedpages 0 0 32 32 0
privvmpages 4587 7289 49152 53575 0
............(more lines like that).........................................

I.e. a container owner can take a glance over the current parameters, their usage and (the thing that is really important) fail counters. Fail counter increases each time a parameter hits the limit. This is very straightforward way for container's owner to see if everything is OK or not.

So, the problems with /sys are:

(1) Gettng such info from 40+ files requires at least some script, while now cat is just fine.

(2) Do we want to virtualize sysfs and enable /sys for every container? Note that user_beancounters statistics is really needed for container's owner to see. At the same time, container's owner should not be able to modify it -- so we should end up with read/write ubc entries for the host system and read-only ones for the container.

Taking into account those two issues, current /proc/user_beancounters might be not that bad.
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