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SubjectRe: [PATCH] Memory Resource Controller Add Boot Option
Paul Menage wrote:
> On Mon, Feb 25, 2008 at 3:55 AM, Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
>>
>> A boot option for the memory controller was discussed on lkml. It is a good
>> idea to add it, since it saves memory for people who want to turn off the
>> memory controller.
>>
>> By default the option is on for the following two reasons
>>
>> 1. It provides compatibility with the current scheme where the memory
>> controller turns on if the config option is enabled
>> 2. It allows for wider testing of the memory controller, once the config
>> option is enabled
>>
>> We still allow the create, destroy callbacks to succeed, since they are
>> not aware of boot options. We do not populate the directory will
>> memory resource controller specific files.
>
> Would it make more sense to have a generic cgroups boot option for this?
>
> Something like cgroup_disable=xxx, which would be parsed by cgroups
> and would cause:
>
> - a "disabled" flag to be set to true in the subsys object (you could
> use this in place of the mem_cgroup_on flag)
>

I thought about it, but it did not work out all that well. The reason being,
that the memory controller is called in from places besides cgroup.
mem_cgroup_charge_common() for example is called from several places in mm.
Calling into cgroups to check, enabled/disabled did not seem right.

Hence I put the boot option in mm/memcontrol.c

> - prevent the disabled cgroup from being bound to any mounted
> hierarchy (so it would be ignored in a mount with no subsystem
> options, and a mount with options that specifically pick that
> subsystem would give an error)
>

The controller can be bound, but I just don't populate the files associated with
the controller

> Paul


--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL


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