From: Balbir Singh <bsingharora@gmail.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org,
Tejun Heo <tj@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>
Subject: Re: [mm v2 0/3] Support memory cgroup hotplug
Date: Wed, 23 Nov 2016 18:50:42 +1100 [thread overview]
Message-ID: <342ebcca-b54c-4bc6-906b-653042caae06@gmail.com> (raw)
In-Reply-To: <20161123072543.GD2864@dhcp22.suse.cz>
On 23/11/16 18:25, Michal Hocko wrote:
> On Wed 23-11-16 15:36:51, Balbir Singh wrote:
>> In the absence of hotplug we use extra memory proportional to
>> (possible_nodes - online_nodes) * number_of_cgroups. PPC64 has a patch
>> to disable large consumption with large number of cgroups. This patch
>> adds hotplug support to memory cgroups and reverts the commit that
>> limited possible nodes to online nodes.
>
> Balbir,
> I have asked this in the previous version but there still seems to be a
> lack of information of _why_ do we want this, _how_ much do we save on
> the memory overhead on most systems and _why_ the additional complexity
> is really worth it. Please make sure to add all this in the cover
> letter.
>
The data is in the patch referred to in patch 3. The order of waste was
200MB for 400 cgroup directories enough for us to restrict possible_map
to online_map. These patches allow us to have a larger possible map and
allow onlining nodes not in the online_map, which is currently a restriction
on ppc64.
A typical system that I use has about 100-150 directories, depending on the
number of users/docker instances/configuration/virtual machines. These numbers
will only grow as we pack more of these instances on them.
>From a complexity view point, the patches are quite straight forward.
> I still didn't get to look into those patches because I am swamped with
> other things but to be honest I do not really see a strong justification
> to make it high priority for me.
>
I am OK if you need more time to review them, but I've been pushing them
to fix the cases I've mentioned above.
Balbir Singh.
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next prev parent reply other threads:[~2016-11-23 7:50 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-23 4:36 [mm v2 0/3] Support memory cgroup hotplug Balbir Singh
2016-11-23 4:36 ` [mm v2 1/3] mm: Add basic infrastructure for memcg hotplug support Balbir Singh
2016-11-23 4:36 ` [mm v2 2/3] mm: Move operations to hotplug callbacks Balbir Singh
2016-11-23 4:36 ` [mm v2 3/3] powerpc/mm: fix node_possible_map limitations Balbir Singh
2016-11-23 7:25 ` [mm v2 0/3] Support memory cgroup hotplug Michal Hocko
2016-11-23 7:50 ` Balbir Singh [this message]
2016-11-23 8:07 ` Michal Hocko
2016-11-23 8:37 ` Balbir Singh
2016-11-23 9:28 ` Michal Hocko
2016-11-23 13:05 ` Balbir Singh
2016-11-23 13:22 ` Michal Hocko
2016-11-28 21:10 ` Tejun Heo
2016-11-29 0:09 ` Balbir Singh
2016-11-29 0:42 ` Tejun Heo
2016-11-29 4:57 ` Balbir Singh
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