Re: [PATCH] memcg: fix typo in the soft_limit stats.

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

On Mon, 16 May 2011 17:05:02 -0700
Ying Han <yinghan@google.com> wrote:

> On Mon, May 16, 2011 at 4:15 PM, Johannes Weiner <hannes@cmpxchg.org> wrote:
> 
> > On Mon, May 16, 2011 at 03:00:30PM -0700, Ying Han wrote:
> > > This fixes the typo in the memory.stat including the following two
> > > stats:
> > >
> > > $ cat /dev/cgroup/memory/A/memory.stat
> > > total_soft_steal 0
> > > total_soft_scan 0
> > >
> > > And change it to:
> > >
> > > $ cat /dev/cgroup/memory/A/memory.stat
> > > total_soft_kswapd_steal 0
> > > total_soft_kswapd_scan 0
> > >
> > > Signed-off-by: Ying Han <yinghan@google.com>
> >
> > I am currently proposing and working on a scheme that makes the soft
> > limit not only a factor for global memory pressure, but for
> > hierarchical reclaim in general, to prefer child memcgs during reclaim
> > that are in excess of their soft limit.
> >
> > Because this means prioritizing memcgs over one another, rather than
> > having explicit soft limit reclaim runs, there is no natural counter
> > for pages reclaimed due to the soft limit anymore.
> >
> > Thus, for the patch that introduces this counter:
> >
> > Nacked-by: Johannes Weiner <hannes@cmpxchg.org>
> >
> 
> This patch is fixing a typo of the stats being integrated into mmotm. Does
> it make sense to fix the
> existing stats first while we are discussing other approaches?
> 

It would be quite bad to add new userspace-visible stats and to then
take them away again.

But given that memcg-add-stats-to-monitor-soft_limit-reclaim.patch is
queued for 2.6.39-rc1, we could proceed with that plan and then make
sure that Johannes's changes are merged either prior to 2.6.40 or
they are never merged at all.

Or we could just leave out the stats until we're sure.  Not having them
for a while is not as bad as adding them and then removing them.

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