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SubjectRe: [ckrm-tech] [PATCH] BC: resource beancounters (v4) (added user memory)
Pavel Emelianov wrote:
> Balbir Singh wrote:
>> Dave Hansen wrote:
>>> On Fri, 2006-09-08 at 11:33 +0400, Pavel Emelianov wrote:
>>>> I'm afraid we have different understandings of what a "guarantee" is.
>>> It appears so.
>>>> Don't we?
>>>> Guarantee may be one of
>>>> 1. container will be able to touch that number of pages
>>>> 2. container will be able to sys_mmap() that number of pages
>>>> 3. container will not be killed unless it touches that number of
>>>> pages
>>> A "death sentence" guarantee? I like it. :)
>>>> 4. anything else
>>>> Let's decide what kind of a guarantee we want.
>> I think of guarantees w.r.t resources as the lower limit on the resource.
>> Guarantees and limits can be thought of as the range (guarantee, limit]
>> for the usage of the resource.
>>> I think of it as: "I will be allowed to use this many total pages, and
>>> they are guaranteed not to fail." (1), I think. The sum of all of the
>>> system's guarantees must be less than or equal to the amount of free
>>> memory on the machine.
>> Yes, totally agree.
> Such a guarantee is really a limit and this limit is even harder than
> BC's one :)
> E.g. I have a node with 1Gb of ram and 10 containers with 100Mb
> guarantee each.
> I want to start one more. What shall I do not to break guarantees?

Don't start the new container or change the guarantees of the existing ones
to accommodate this one :) The QoS design (done by the administrator) should
take care of such use-cases. It would be perfectly ok to have a container
that does not care about guarantees to set their guarantee to 0 and set
their limit to the desired value. As Chandra has been stating we need two
parameters (guarantee, limit), either can be optional, but not both.

>>> If we knew to which NUMA node the memory was going to go, we might as
>>> well take the pages out of the allocator.
>>> -- Dave


Balbir Singh,
Linux Technology Center,
IBM Software Labs
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