Re: [LSF/MM TOPIC][ATTEND] memcg topics.

[Glauber Costa <glommer@parallels.com>]

On 02/01/2012 12:58 PM, Glauber Costa wrote:
> On 02/01/2012 04:55 AM, KAMEZAWA Hiroyuki wrote:
>> Hi, I guess we have some topics on memory cgroups.
>>
>> 1-4 : someone has an implemanation
>> 5 : no implemenation.
>>
>> 1. page_cgroup diet
>> memory cgroup uses 'struct page_cgroup', it was 40bytes per 4096bytes
>> in past.
>> Johannes removed ->page and ->lru from page_cgroup, then now,
>> sizeof(page_cgroup)==16. Now, I'm working on removing ->flags to make
>> sizeof(page_cgroup)==8.
>>
>> Then, finally, page_cgroup can be moved into struct page on 64bit
>> system ?
>> How 32bit system will be ?
>>
>> 2. memory reclaim
>> Johannes, Michal and Ying, ant others, are now working on memory
>> reclaim problem
>> with new LRU. Under it, LRU is per-memcg-per-zone.
>> Following topics are discussed now.
>>
>> - simplificaiton/re-implemenation of softlimit
>> - isolation of workload (by softlimit)
>> - when we should stop memory reclaim, especially under direct-reclaim.
>> (Now, we scan all zonelist..)
>>
>> 3. per-memcg-lru-zone-lru-lock
>> I hear Hugh Dickins have some patches and are testing it.
>> It will be good to discuss this if it has Pros. and Cons or
>> implemenation issue.
>>
>> 4. dirty ratio
>> In the last year, patches were posted but not merged. I'd like to hear
>> works on this area.
>>
>> 5. accounting other than user pages.
>> Last year, tcp buffer limiting was added to "memcg".
> I was about to correct you about "last year", when suddenly my mind went
> "oh god, this is 2012!"
>
>> If someone has other plans, I'd like to hear.
>> I myself don't think 'generic kernel memory limitation' is a good
>> thing....
>> admins can't predict performance.
>>
>> Can we make accounting on dentry/inode into memcg and call
>> shrink_slab() ?
>> But I guess per-zone-shrink-slab() should go 1st...
>
> Well, I have work in progress to continue that. There are a couple of
> slabs I'd like to track. I am convinced that a generic framework is a
> good thing, but indeed, I am still not sure if a generic interface is.
>
> The advantage of keeping it unified, is that it prevents the number of
> knobs from exploding. For us, this is not that much of a problem,
> because there are only a couple of ones we are interested in. dcache and
> inode is an example of that: when we sent out some proposals (that
> didn't use memcg), some people wanted to see inode, not dcache being
> tracked. We disagreed. But yet, the truth remains that only *one* of
> them needs to be tracked, because they live in a close relation to each
> other. So if we manage to find a couple of slabs that are key to that,
> we can limit only those.
>
> Well, that was food for thought only. I do think this is a nice topic.
>
> Also, there is no serious implementation for that, as you mentioned, but
> a series of patches were sent out for appreciation last year. So there
> is at least a basis for starting
>
Forgot to add [ATTEND] to the subject. I'd like to attend to discuss that.

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