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Re: [RFC/PATCH] cgroup swap subsystem [message #28031] Thu, 06 March 2008 08:33 Go to next message
KAMEZAWA Hiroyuki is currently offline  KAMEZAWA Hiroyuki
Messages: 463
Registered: September 2006
Senior Member
On Thu, 06 Mar 2008 11:20:17 +0300
Pavel Emelyanov <xemul@openvz.org> wrote:

> KAMEZAWA Hiroyuki wrote:
> > On Wed, 05 Mar 2008 17:14:12 +0300
> > Pavel Emelyanov <xemul@openvz.org> wrote:
> >>> Strongly agree.  Nobody's interested in swap as such: it's just
> >>> secondary memory, where RAM is primary memory.  People want to
> >>> control memory as the sum of the two; and I expect they may also
> >>> want to control primary memory (all that the current memcg does)
> >>> within that.  I wonder if such nesting of limits fits easily
> >>> into cgroups or will be problematic.
> >> This nesting would affect the res_couter abstraction, not the
> >> cgroup infrastructure. Current design of resource counters doesn't
> >> allow for such thing, but the extension is a couple-of-lines patch :)
> >>
> > IMHO, keeping res_counter simple is better.
> > 
> > Is this kind of new entry in mem_cgroup not good ?
> > ==
> > struct mem_cgroup {
> > 	...
> > 	struct res_counter	memory_limit.
> > 	struct res_counter	swap_limit.
> > 	..
> > }
> 
> I meant the same thing actually. By "nesting would affect" I
> meant, that we might want to make res_counters hierarchical.
> 
> That would kill two birds with one stone - we will make a true
> hierarchical memory accounting and let charging of two counters
> with one call.

Hierarchical res_counter makes sense.
Making it in simple/reasonable style will be our challenge. 

Thanks,
-Kame

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Re: [RFC/PATCH] cgroup swap subsystem [message #28033 is a reply to message #28031] Thu, 06 March 2008 08:38 Go to previous messageGo to next message
Pavel Emelianov is currently offline  Pavel Emelianov
Messages: 1149
Registered: September 2006
Senior Member
KAMEZAWA Hiroyuki wrote:
> On Thu, 06 Mar 2008 11:20:17 +0300
> Pavel Emelyanov <xemul@openvz.org> wrote:
> 
>> KAMEZAWA Hiroyuki wrote:
>>> On Wed, 05 Mar 2008 17:14:12 +0300
>>> Pavel Emelyanov <xemul@openvz.org> wrote:
>>>>> Strongly agree.  Nobody's interested in swap as such: it's just
>>>>> secondary memory, where RAM is primary memory.  People want to
>>>>> control memory as the sum of the two; and I expect they may also
>>>>> want to control primary memory (all that the current memcg does)
>>>>> within that.  I wonder if such nesting of limits fits easily
>>>>> into cgroups or will be problematic.
>>>> This nesting would affect the res_couter abstraction, not the
>>>> cgroup infrastructure. Current design of resource counters doesn't
>>>> allow for such thing, but the extension is a couple-of-lines patch :)
>>>>
>>> IMHO, keeping res_counter simple is better.
>>>
>>> Is this kind of new entry in mem_cgroup not good ?
>>> ==
>>> struct mem_cgroup {
>>> 	...
>>> 	struct res_counter	memory_limit.
>>> 	struct res_counter	swap_limit.
>>> 	..
>>> }
>> I meant the same thing actually. By "nesting would affect" I
>> meant, that we might want to make res_counters hierarchical.
>>
>> That would kill two birds with one stone - we will make a true
>> hierarchical memory accounting and let charging of two counters
>> with one call.
> 
> Hierarchical res_counter makes sense.
> Making it in simple/reasonable style will be our challenge. 

I have this in my TODO list. Since this is not so urgent, then if you
don't mind I can prepare the patches next week - after I set the git 
tree up. This change doesn't seem that big.

> Thanks,
> -Kame
> 
> 

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Re: Re: [RFC/PATCH] cgroup swap subsystem [message #28034 is a reply to message #28033] Thu, 06 March 2008 08:48 Go to previous messageGo to next message
Paul Menage is currently offline  Paul Menage
Messages: 642
Registered: September 2006
Senior Member
On Thu, Mar 6, 2008 at 12:38 AM, Pavel Emelyanov <xemul@openvz.org> wrote:
>  > Hierarchical res_counter makes sense.
>  > Making it in simple/reasonable style will be our challenge.
>
>  I have this in my TODO list. Since this is not so urgent, then if you
>  don't mind I can prepare the patches next week - after I set the git
>  tree up. This change doesn't seem that big.
>

The change that you're referring to is allowing a cgroup to have a
total memory limit for itself and all its children, and then giving
that cgroup's children separate memory limits within that overall
limit?

Paul
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Re: Re: [RFC/PATCH] cgroup swap subsystem [message #28037 is a reply to message #28034] Thu, 06 March 2008 08:50 Go to previous message
Pavel Emelianov is currently offline  Pavel Emelianov
Messages: 1149
Registered: September 2006
Senior Member
Paul Menage wrote:
> On Thu, Mar 6, 2008 at 12:38 AM, Pavel Emelyanov <xemul@openvz.org> wrote:
>>  > Hierarchical res_counter makes sense.
>>  > Making it in simple/reasonable style will be our challenge.
>>
>>  I have this in my TODO list. Since this is not so urgent, then if you
>>  don't mind I can prepare the patches next week - after I set the git
>>  tree up. This change doesn't seem that big.
>>
> 
> The change that you're referring to is allowing a cgroup to have a
> total memory limit for itself and all its children, and then giving
> that cgroup's children separate memory limits within that overall
> limit?

Yup. Isn't this reasonable? 

Without this, if I'm a task in a 1GB limited cgroup, I can create a new 
one, set 2GB limit and spawn a kid into it (or move there myself) and be 
happy with 2GB of memory... With the proposed change, even if I set a 2GB
for a subgroup it will not pass _my_ (1GB) limit.

> Paul
> 

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