[Devel] Re: [RFC][PATCH] allow "unlimited" limit value.

[Balbir Singh]

Pavel Emelyanov wrote:
> Balbir Singh wrote:
>> KAMEZAWA Hiroyuki wrote:
>>> On Tue, 25 Sep 2007 16:19:18 +0530
>>> Balbir Singh <balbir at linux.vnet.ibm.com> wrote:
>>>
>>>> Hi, Kamezawa-San,
>>>>
>>> Hi,
>>>
>>>> Your changes make sense, but not CLUI (Command Line Usage) sense.
>>>> 1. The problem is that when we mix strings with numbers, tools that
>>>>    parse/use get confused and complicated
>>> yes, maybe.
>>>
>>>> 2. ULONGLONG_MAX is a real limit, there is no such thing as unlimited.
>>>>    If the user does ever go beyond ULONGLONG_MAX, we will limit him :-)
>>>>
>>> Oh. res_counter.c  uses LONGLONG_MAX as default value.
>>> need fix ? or intended ?
>> Pavel do you remember why LONG was chosen instead of ULONG?
> 
> To prevent the overflow in "charge" routine.
> See, if you add two numbers less than LONG_MAX, but with
> unsigned long type each, you will never have an overflowed result.
> 

Aah.. Thanks, my memory short circuited on me.

>>> And okay there is no "unlimited" state.
>>>
>>>> Having said that, I do wish to have a more intuitive interface for
>>>> users. May be a perl/python script to hide away the numbers game
>>>> from the users. What do you think?
>>>>
>>> I agree with you that perl/python script can hide details. but they need knowledge
>>> about the maximum value, which is given as default value.
>>>
>>> In short, what I want is some value like RLIM_INFINITY in ulimit.
>>>
>> I like the idea of RLIM_INFINITY and how ulimit as a tool shows
>> a value. I guess we need something like RES_COUNTER_LIMIT_MAX
>> and the user tool can show the limit as maximum. We could also
>> define a special number, RES_COUNTER_LIMIT_INFINITY, such that
>> containers will not enforce limits when the limit is set to
>> this value.
>>
>>> Because it seems that res_counter.c will be used for other resouce control purpose,
>>> I thought some generic way (value) to know/specify "the maximum value" is helpful for
>>> all resource controller interface.
>>>
>>> If there is an concensus that treaing ULONGLONG_MAX as default, it's ok.
>>>
>> When I worked on the first version of res_counters, I used 0 to indicate
>> unlimited. When Pavel posted his version, I think derived from
>> beancounters, we did not want to have unlimited containers, so he used
>> the maximum value
> 
> Yup! Setting LONGMAX pages for container means that this container
> is unlimited, since there're no such many pages on any arch :)
> 

Pavel, we no longer account in pages, we do it in bytes. Second,
this assumption cannot hold for long, memory sizes are growing,
I think we need a special value.


>>> Thanks,
>>> -Kame
>>>
>> Thanks for looking into this,
>>
> 


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