[Devel] Re: [ckrm-tech] [RFC][PATCH] UBC: user resource beancounters

[Kirill Korotaev]

Chandra Seetharaman wrote:
> On Fri, 2006-08-18 at 14:36 +0400, Kirill Korotaev wrote:
> 
>>Chandra Seetharaman wrote:
>>
>>>On Thu, 2006-08-17 at 17:55 +0400, Kirill Korotaev wrote:
>>>
>>>
>>>>>On Wed, Aug 16, 2006 at 07:24:03PM +0400, Kirill Korotaev wrote:
>>>>>
>>>>>
>>>>>
>>>>>>As the first step we want to propose for discussion
>>>>>>the most complicated parts of resource management:
>>>>>>kernel memory and virtual memory.
>>>>>
>>>>>Do you have any plans to post a CPU controller? Is that tied to UBC
>>>>>interface as well?
>>>>
>>>>Not everything at once :) To tell the truth I think CPU controller
>>>>is even more complicated than user memory accounting/limiting.
>>>>
>>>>No, fair CPU scheduler is not tied to UBC in any regard.
>>>
>>>
>>>Not having the CPU controller on UBC doesn't sound good for the
>>>infrastructure. IMHO, the infrastructure (for resource management) we
>>>are going to have should be able to support different resource
>>>controllers, without each controllers needing to have their own
>>>infrastructure/interface etc.,
>>
>>1. nothing prevents fair cpu scheduler from using UBC infrastructure.
> 
> 
> ok.
> 
> 
>>   but currently we didn't start discussing it.
>>
>>2. as was discussed with a number of people on summit we agreed that
>>   it maybe more flexible to not merge all resource types into one set.
>>   CPU scheduler is usefull by itself w/o memory management.
>>   the same for disk I/O bandwidht which is controlled in CFQ by
>>   a separate system call.
>>
>>   it is also more logical to have them separate since they
>>   operate in different terms. For example, for CPU it is
>>   shares which are relative units, while for memory it is
>>   absolute units in bytes.
> 
> 
> We don't have to tie the units with the number. We can leave it to be
> sorted out between the user and the controller writer.
> 
> Current implementation of resource groups does that.
> 
> 
>>>>As we discussed before, it is valuable to have an ability to limit
>>>>different resources separately (CPU, disk I/O, memory, etc.).
>>>
>>>Having ability to limit/control different resources separately not
>>>necessarily mean we should have different infrastructure for each.
>>
>>I'm not advocating to have a different infrastructure.
>>It is not the topic I raise with this patch set.
>>
>>
>>>>For example, it can be possible to place some mission critical
>>>>kernel threads (like kjournald) in a separate contanier.
>>>
>>>I don't understand the comment above (in this context).
>>
>>If you have a single container controlling all the resources, then
>>placing kjournald into CPU container would require setting
>>it's memory limits etc. And kjournald will start to be accounted separately,
> 
> 
> Not necessarily. You could just set the CPU shares of the group and
> leave the other resources as don't care.
don't care IMHO doesn't mean "accounted and limited as container X".
it sounds like "no limits" for me.

>>while my intention is kjournald to be accounted as the host system.
>>I only want to _guarentee_ some CPU to it.
> I do not see any _guarantee_ support, only barrier(soft limit) and
> limit. May be I overlooked. Can you tell me how guarantee is achieved
> with UBC.
we just provide additional parameters like oomguarpages, where barrier
is a guarantee.

Kirill