Re: [PATCH] Cpu statistics accounting based on Paul Menage patches

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 11 Apr 2007 19:02:27 +0400
Pavel Emelianov <xemul@sw.ru> wrote:

> Provides a per-container statistics concerning the numbers of tasks
> in various states, system and user times, etc. Patch is inspired
> by Paul's example of the used CPU time accounting. Although this
> patch is independent from Paul's example to make it possible playing
> with them separately.

Why is this actually needed?  If userspace has a list of the tasks which
are in a particular container, it can run around and add up the stats for
those tasks without kernel changes?

It's a bit irksome that we have so much accounting of this form in core
kernel, yet we have to go and add a completely new implementation to create
something which is similar to what we already have.  But I don't
immediately see a fix for that.  Apart from paragraph #1 ;)

Should there be linkage between per-container stats and
delivery-via-taskstats?  I can't think of one, really.

You have cpu stats.  Later, presumably, we'll need IO stats, MM stats,
context-switch stats, number-of-syscall stats, etc, etc.  Are we going to
reimplement all of those things as well?  See paragraph #1!

Bottom line: I think we seriously need to find some way of consolidating
per-container stats with our present per-task stats.  Perhaps we should
instead be looking at ways in which we can speed up paragraph #1.