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Re: [PATCH v3 04/13] kmem accounting basic infrastructure [message #48153 is a reply to message #48150]

Mon, 01 October 2012 08:43

Glauber Costa
Messages: 916
Registered: October 2011

Senior Member

On 10/01/2012 04:57 AM, Tejun Heo wrote:
> Hello, James.
>
> On Sun, Sep 30, 2012 at 12:25:52PM +0100, James Bottomley wrote:
>> But you've got to ask yourself who cares about accurate accounting per
>> container of dentry and inode objects? They're not objects that any
>> administrator is used to limiting. What we at parallels care about
>> isn't accurately accounting them, it's that one container can't DoS
>> another by exhausting system resources. That's achieved equally well by
>> first charge slab accounting, so we don't really have an interest in
>> pushing object accounting code for which there's no use case.
>
> Isn't it more because the use cases you have on mind don't share
> dentries/inodes too much? Wildly incorrect accounting definitely
> degrades container isolation and can lead to unexpected behaviors.
>
>> All we need kernel memory accounting and limiting for is DoS prevention.
>> There aren't really any system administrators who care about Kernel
>> Memory accounting (at least until the system goes oom) because there are
>> no absolute knobs for it (all there is are a set of weird and wonderful
>> heuristics, like dirty limit ratio and drop caches). Kernel memory
>
> I think that's because the mechanism currently doesn't exist. If one
> wants to control how memory is distributed across different cgroups,
> it's logical to control kernel memory too. The resource in question
> is the actual memory after all. I think at least google would be
> interested in it, so, no, I don't agree that nobody wants it. If that
> is the case, we're working towards the wrong direction.
>
>> usage has a whole set of regulatory infrastructure for trying to make it
>> transparent to the user.
>>
>> Don't get me wrong: if there were some easy way to get proper memory
>> accounting for free, we'd be happy but, because it has no practical
>> application for any of our customers, there's a limited price we're
>> willing to pay to get it.
>
> Even on purely technical ground, it could be that first-use is the
> right trade off if other more accurate approaches are too difficult
> and most workloads are happy with such approach. I'm still a bit
> weary to base userland interface decisions on that tho.
>

For the record, user memory also suffers a bit from being always
constrained to first-touch accounting. Greg Thelen is working on
alternative solutions to make first-accounting the default in a
configurable environment, as he explained in the kernel summit.

When that happens, kernel memory can take advantage of it for free.

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[Message index]

		[PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Tue, 18 September 2012 14:04
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Fri, 21 September 2012 16:34
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Mon, 24 September 2012 08:09
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Michal Hocko on Wed, 26 September 2012 14:03
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Wed, 26 September 2012 14:33
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Michal Hocko on Wed, 26 September 2012 16:01
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Wed, 26 September 2012 17:34
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Wed, 26 September 2012 16:36
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Wed, 26 September 2012 17:36
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Wed, 26 September 2012 17:44
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Wed, 26 September 2012 17:53
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Wed, 26 September 2012 18:01
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Wed, 26 September 2012 18:56
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Wed, 26 September 2012 19:34
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Wed, 26 September 2012 19:46
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Wed, 26 September 2012 19:56
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Wed, 26 September 2012 20:02
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Wed, 26 September 2012 20:16
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Wed, 26 September 2012 21:24
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Wed, 26 September 2012 22:10
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Wed, 26 September 2012 22:29
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Wed, 26 September 2012 22:42
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Wed, 26 September 2012 22:54
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Wed, 26 September 2012 23:08
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Wed, 26 September 2012 23:20
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Wed, 26 September 2012 23:33
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Michal Hocko on Thu, 27 September 2012 12:15
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Thu, 27 September 2012 12:20
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Michal Hocko on Thu, 27 September 2012 12:40
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Thu, 27 September 2012 12:40
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Michal Hocko on Thu, 27 September 2012 12:54
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Mel Gorman on Thu, 27 September 2012 14:28
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Thu, 27 September 2012 14:49
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Thu, 27 September 2012 14:57
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Thu, 27 September 2012 17:46
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Michal Hocko on Thu, 27 September 2012 17:56
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Thu, 27 September 2012 18:45
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Sun, 30 September 2012 07:57
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Sun, 30 September 2012 08:02
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: James Bottomley on Sun, 30 September 2012 08:56
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Sun, 30 September 2012 10:37
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: James Bottomley on Sun, 30 September 2012 11:25
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Mon, 01 October 2012 00:57
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Mon, 01 October 2012 08:43
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Mon, 01 October 2012 08:46
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Wed, 03 October 2012 22:59
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Mon, 01 October 2012 08:36
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Michal Hocko on Thu, 27 September 2012 12:08
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Thu, 27 September 2012 12:11
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Thu, 27 September 2012 14:33
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Mel Gorman on Thu, 27 September 2012 14:43
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Thu, 27 September 2012 14:58
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Thu, 27 September 2012 18:30
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Sun, 30 September 2012 08:23
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Mon, 01 October 2012 08:45
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Wed, 03 October 2012 22:54
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Thu, 04 October 2012 11:55
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Sat, 06 October 2012 02:19
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Michal Hocko on Thu, 27 September 2012 15:09
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Sun, 30 September 2012 08:47
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Michal Hocko on Mon, 01 October 2012 09:27
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Tejun Heo on Wed, 03 October 2012 22:43
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Michal Hocko on Fri, 05 October 2012 13:47
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Johannes Weiner on Wed, 26 September 2012 22:11
		Re: [PATCH v3 04/13] kmem accounting basic infrastructure By: Glauber Costa on Wed, 26 September 2012 22:45

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