[Devel] Re: [ckrm-tech] [PATCH] BC: resource beancounters (v4) (added user memory)

[Balbir Singh]

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