Re: boot cgroup questions

From: Max Krasnyansky
Date: Tue Mar 11 2008 - 22:53:21 EST




Paul Menage wrote:
> On Tue, Mar 11, 2008 at 7:34 PM, Max Krasnyansky <maxk@xxxxxxxxxxxx> wrote:
>> Suppose we were to do it from kernel. What's the right way to create a cgroup
>> without mounting a cgroupfs ?
>
> There isn't really a way, but you could always kern_mount() a
> filesystem inside the kernel.
Aha, that's what I was missing. kern_mount(). Cool :).

>> I just want to play with it. There are a couple of advantages that I see for
>> doing it from kernel. We can move 'kthreadd' and idle threads into the 'boot'
>> cgroup early on and therefor later on won't even have to iterate through the
>> tasks and stuff.
>
> Would this be done based on some boot commandline option? I don't
> think you'd want to do it unconditionally.
Hmm, I believe the original discussion was about doing it unconditionally.
Why not I guess ? It probably won't even affect your existing scripts since
they will be able to move tasks into another set just like they do now. The
only thing I can think of is that if your scripts use sched_load_balance then
they will now have to unset it in the 'boot' set as well. Otherwise since the
'boot' set will be non-exclusive (cpus and mems) it should not really affect
anything.
So what's your concern with unconditional 'boot' cgroup/cpuset ?

Max
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