On Fri 12-10-12 11:36:38, Glauber Costa wrote:

On 10/11/2012 02:11 PM, Michal Hocko wrote:

quoted

On Mon 08-10-12 14:06:10, Glauber Costa wrote:

[...]

quoted

quoted

+	if (!memcg->kmem_accounted && val != RESOURCE_MAX) {

Just a nit but wouldn't memcg_kmem_is_accounted(memcg) be better than
directly checking kmem_accounted?
Besides that I am not sure I fully understand RESOURCE_MAX test. Say I
want to have kmem accounting for monitoring so I do 
echo -1 > memory.kmem.limit_in_bytes

so you set the value but do not activate it. Isn't this just a reminder
from the time when the accounting could be deactivated?

No, not at all.

I see you have talked about that in other e-mails, (I was on sick leave
yesterday), so let me consolidate it all here:

What we discussed before, regarding to echo -1 > ... was around the
disable code, something that we no longer allow. So now, if you will
echo -1 to that file *after* it is limited, you get in track only mode.

But for you to start that, you absolutely have to write something
different than -1.

Just one example: libcgroup, regardless of how lame we think it is in
this regard, will write to all cgroup files by default when a file is
updated. If you haven't written anything, it will still write the same
value that the file had before.

Ohh, I wasn't aware of that and it sounds pretty lame.
 

This means that an already deployed libcg-managed installation will
suddenly enable kmem for every cgroup. Sure this can be fixed in
userspace, but:

1) There is no reason to break it, if we can

You are right

2) It is perfectly reasonable to expect that if you write to a file the
same value that was already there, nothing happens.

Fair enough

-- 
Michal Hocko
SUSE Labs