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Re: [PATCH v3 04/13] kmem accounting basic infrastructure [message #48207 is a reply to message #48201]

Thu, 04 October 2012 11:55

Glauber Costa
Messages: 916
Registered: October 2011

Senior Member

On 10/04/2012 02:54 AM, Tejun Heo wrote:
> Hello, Glauber.
>
> On Mon, Oct 01, 2012 at 12:45:11PM +0400, Glauber Costa wrote:
>>> where kmemcg_slab_idx is updated from sched notifier (or maybe add and
>>> use current->kmemcg_slab_idx?). You would still need __GFP_* and
>>> in_interrupt() tests but current->mm and PF_KTHREAD tests can be
>>> rolled into index selection.
>>
>> How big would this array be? there can be a lot more kmem_caches than
>> there are memcgs. That is why it is done from memcg side.
>
> The total number of memcgs are pretty limited due to the ID thing,
> right? And kmemcg is only applied to subset of caches. I don't think
> the array size would be a problem in terms of memory overhead, would
> it? If so, RCU synchronize and dynamically grow them?
>
> Thanks.
>

I don't want to assume the number of memcgs will always be that limited.
Sure, the ID limitation sounds pretty much a big one, but people doing
VMs usually want to stack as many VMs as they possibly can in an
environment, and the less things preventing that from happening, the better.

That said, now that I've experimented with this a bit, indexing from the
cache may have some advantages: it can get too complicated to propagate
new caches appearing to all memcgs that already in-flight. We don't have
this problem from the cache side, because instances of it are guaranteed
not to exist at this point by definition.

I don't want to bloat unrelated kmem_cache structures, so I can't embed
a memcg array in there: I would have to have a pointer to a memcg array
that gets assigned at first use. But if we don't want to have a static
number, as you and christoph already frowned upon heavily, we may have
to do that memcg side as well.

The array gets bigger, though, because it pretty much has to be enough
to accomodate all css_ids. Even now, they are more than the 400 I used
in this patchset. Not allocating all of them at once will lead to more
complication and pointer chasing in here.

I'll take a look at the alternatives today and tomorrow.

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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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