Re: memcg creates an unkillable task in 3.2-rc2
From: Eric W. Biederman
Date: Mon Jul 29 2013 - 14:52:38 EST
Johannes Weiner <hannes@xxxxxxxxxxx> writes:
> On Mon, Jul 29, 2013 at 10:03:35AM -0700, Eric W. Biederman wrote:
>> Yes. From the looks of the looks of it the cgroup implementation is
>> rather badly borked right now, and definitely not up to the standards of
>> the other core pieces of the kernel. One of the reasons I was rather
>> apalled when systemd started using them. Until the code actually works
>> reliably and the races are removed most people's systems would be much
>> better off with cgroups compiled out.
>> A single unified hierarchy is a really nasty idea for the same set of
>> reasons. You have to recompile to disable a controller to see if it that
>> controller's bugs are what are causing problems on your production
>> system. Compiles or even just a reboot is a very heavy hammer to ask
>> people to use when they are triaging a problem.
> That's not how it works. You can always select which controllers you
> want to mount during runtime. Unified hierarchy only means that there
> is one cgroup tree for all mounted controllers, rather than every
> controller having its own separate cgroup tree.
> If you are like most users and currently mount all controllers in the
> same directory so that their cgroup trees overlap and appear to be a
> single tree, nothing changes for you.
My practical need is that I need the ability modify which controllers I
am using on a per group basis. So that I can make corrall new processes
in a different set of controllers than currently existing processes.
I might just be missing something but I don't see how to do that with
all of the controllers mounted to the same filesystem.
So while I currently have a single mount of cgroupfs, and don't yet see
a need for orthogonal classification of processes. To keep bugs and
craziness under control I expect I will be implementing a mount of
cgroupfs per controller within a month.
But except for the need to limit the scope of bugs this is all getting
rather badly off topic.
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