On Tue 26-06-12 22:22:04, Glauber Costa wrote:

On 06/26/2012 10:12 PM, Tejun Heo wrote:

quoted

On Tue, Jun 26, 2012 at 05:30:28PM +0400, Glauber Costa wrote:

quoted

Okay, so after recent discussions, I am proposing the following
patch. It won't remove hierarchy, or anything like that. Just default
to true in the root cgroup, and print a warning once if you try
to set it back to 0.

I am not adding it to feature-removal-schedule.txt because I don't
view it as a consensus. Rather, changing the default would allow us
to give it a time around in the open, and see if people complain
and what we can learn about that.

Signed-off-by: Glauber Costa <redacted>
CC: Michal Hocko <redacted>
CC: Kamezawa Hiroyuki <redacted>
CC: Johannes Weiner <redacted>
CC: Tejun Heo <redacted>

Just in case it wasn't clear in the other posting.

 Nacked-by: Tejun Heo [off-list ref]

You can't change the default behavior silently.  Not in this scale.

Thanks.

I certainly don't share your views of the matter here.

I would agree with you if we were changing a fundamental algorithm,
with no way to resort back to a default setup. We are not removing any
functionality whatsoever here.

I would agree with you if we were actually documenting explicitly
that this is an expected default behavior.

Actually we did:
Documentation/cgroups/memory.txt
"
6.1 Enabling hierarchical accounting and reclaim

A memory cgroup by default disables the hierarchy feature. Support
can be enabled by writing 1 to memory.use_hierarchy file of the root
cgroup
"

But I do not think this is really that important. We are still
interested in making the thing sane. Flat_hierarchical trees just don't
seem right... Generic? Sure. Sane? Really?

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic