From: Waiman Long <longman@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Li Zefan <lizefan@huawei.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Ingo Molnar <mingo@redhat.com>,
cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-doc@vger.kernel.org, kernel-team@fb.com, pjt@google.com,
luto@amacapital.net, Mike Galbraith <efault@gmx.de>,
torvalds@linux-foundation.org, Roman Gushchin <guro@fb.com>,
Juri Lelli <juri.lelli@redhat.com>,
Patrick Bellasi <patrick.bellasi@arm.com>
Subject: Re: [PATCH v11 7/9] cpuset: Expose cpus.effective and mems.effective on cgroup v2 root
Date: Thu, 19 Jul 2018 11:52:46 -0400 [thread overview]
Message-ID: <de6f931d-613a-3e6a-2a4d-0e49b3bfe2e5@redhat.com> (raw)
In-Reply-To: <20180719153045.GT72677@devbig577.frc2.facebook.com>
On 07/19/2018 11:30 AM, Tejun Heo wrote:
> Hello,
>
> On Thu, Jul 19, 2018 at 10:04:54AM -0400, Waiman Long wrote:
>>> Why would a container not be allowed to create partitions for its
>>> various RT workloads?
>> As far as I understand, Tejun has some concern about the way that
>> partitioning works is inconsistent with how other resources are being
>> managed by cgroup v2 controllers. I adds an incremental patch to
>> temporarily disable the creation of partition below the first level
>> children to buy us time so that we can reach a compromise later on what
>> to do. We can always add features, but taking away features after they
>> are made available will be hard.
>>
>> I am fine either way. It is up to you and Tejun to figure out what
>> should be made available to the users.
> So, the main thing is that putting a cpu into a partition locks away
> the cpu from its ancestors. That's a system level operation which
> isn't delegatable. If we want to allow partitioning in subtrees, the
> parent still be able to take away partitioned cpus too even if that
> means ignoring descendants' configurations, which btw is exactly what
> cpuset does for non-partition configs.
>
> I don't think this would be technically too challenging to implement,
> but unless there are immediate use cases for it, we can start simpler
> & restricted.
>
> Thanks.
>
BTW, the way the partition is currently implemented right now is that a
child cannot be a partition root unless its parent is a partition root
itself. That is to avoid turning on partition to affect ancestors
further up the hierarchy than just the parent. So in the case of a
container, it cannot allocate sub-partitions underneath it unless it is
a partition itself. Will that solve your concern?
Thanks,
Longman
next prev parent reply other threads:[~2018-07-19 15:52 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-24 7:30 [PATCH v11 0/9] cpuset: Enable cpuset controller in default hierarchy Waiman Long
2018-06-24 7:30 ` [PATCH v11 1/9] " Waiman Long
2018-06-24 7:30 ` [PATCH v11 2/9] cpuset: Add new v2 cpuset.sched.partition flag Waiman Long
2018-06-24 7:30 ` [PATCH v11 3/9] cpuset: Simulate auto-off of sched.partition at cgroup removal Waiman Long
2018-06-24 7:30 ` [PATCH v11 4/9] cpuset: Allow changes to cpus in a partition root Waiman Long
2018-06-24 7:30 ` [PATCH v11 5/9] cpuset: Make sure that partition flag work properly with CPU hotplug Waiman Long
2018-06-24 7:30 ` [PATCH v11 6/9] cpuset: Make generate_sched_domains() recognize reserved_cpus Waiman Long
2018-06-24 7:30 ` [PATCH v11 7/9] cpuset: Expose cpus.effective and mems.effective on cgroup v2 root Waiman Long
2018-07-02 16:53 ` Tejun Heo
2018-07-03 0:41 ` Waiman Long
2018-07-03 15:58 ` Tejun Heo
2018-07-06 20:32 ` Waiman Long
2018-07-10 15:23 ` Waiman Long
2018-07-18 15:21 ` Waiman Long
2018-07-18 15:31 ` Tejun Heo
2018-07-18 21:12 ` Waiman Long
2018-07-19 13:52 ` Peter Zijlstra
2018-07-19 14:04 ` Waiman Long
2018-07-19 15:30 ` Tejun Heo
2018-07-19 15:52 ` Waiman Long [this message]
2018-07-19 16:52 ` Tejun Heo
2018-07-19 17:22 ` Waiman Long
2018-07-19 17:25 ` Tejun Heo
2018-07-19 17:38 ` Waiman Long
2018-07-20 11:32 ` Peter Zijlstra
2018-07-20 11:31 ` Peter Zijlstra
2018-07-20 11:45 ` Tejun Heo
2018-07-20 12:04 ` Tejun Heo
2018-07-20 15:44 ` Peter Zijlstra
2018-07-20 15:56 ` Tejun Heo
2018-07-20 16:19 ` Waiman Long
2018-07-20 16:37 ` Peter Zijlstra
2018-07-20 17:09 ` Waiman Long
2018-07-20 17:41 ` Tejun Heo
2018-08-13 17:56 ` Waiman Long
2018-08-17 15:59 ` Tejun Heo
2018-08-18 1:03 ` Waiman Long
2018-07-27 21:21 ` Waiman Long
2018-07-20 16:25 ` Peter Zijlstra
2018-07-20 15:57 ` Waiman Long
2018-07-20 11:29 ` Peter Zijlstra
2018-06-24 7:30 ` [PATCH v11 8/9] cpuset: Don't rebuild sched domains if cpu changes in non-partition root Waiman Long
2018-06-24 7:30 ` [PATCH v11 9/9] cpuset: Allow reporting of sched domain generation info Waiman Long
2018-07-19 13:54 ` Peter Zijlstra
2018-07-19 13:56 ` Waiman Long
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