From: Waiman Long <longman@redhat.com>
To: Tejun Heo <tj@kernel.org>, Peter Zijlstra <peterz@infradead.org>
Cc: 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: Fri, 20 Jul 2018 12:19:29 -0400 [thread overview]
Message-ID: <4857a9db-ebf5-24f8-c42d-d795f5c75854@redhat.com> (raw)
In-Reply-To: <20180720155613.GB1934745@devbig577.frc2.facebook.com>
On 07/20/2018 11:56 AM, Tejun Heo wrote:
> Hello, Peter.
>
> On Fri, Jul 20, 2018 at 05:44:54PM +0200, Peter Zijlstra wrote:
>>> The currently proposed implementation is somewhere in the middle. It
>>> kinda gets there by restricting a partition to be a child of another
>>> partition, which may be okay but it does make the whole delegation
>>> mechanism less useful.
>> So the implementation does not set ownership of the 'partition' file to
>> that of the parent directory? Because _that_ is what I understood from
>> Waiman (many versions ago). And that _does_ allow delegation to work
>> nicely.
> So, that part isn't the problem. The problem is that if we allow
> partitioning nested further away from ancestor, the descendant would
> be able to take away reources from the removed ancestor. Waiman
> avoids this problem by only allowing partitions to nest but then it's
> kinda weird cuz it's just a separate tree.
The rationale behind the current design is that a parent is allowed to
create a child partition if it fully owns all the cpus it has. That is
true only if it is a partition itself. IOW, making a cpuset a partition
won't affect any ancestors other than the parent.
>>>>> 2. take away any given cpu from ist subtree.
>>>> I really hate this obsession of yours and doubly so for partitions. But
>>>> why would this currently not be allowed?
>>> Well, sorry that you hate it. It's a fundamental architectural
>>> constraint. If it can't satisfy that, it should't be in cgroup.
>> So is hierarchical behaviour; but you seem willing to forgo that.
> Well, we do have root or first-level only things. Things just need to
> be properly delegatable when they're hierarchical (and things should
> be hierarchical only when that actually means something). While not
> desirable, considering the history, accomodating this specific usage
> that way seems acceptable to me.
I am not against the idea of making it hierarchical eventually. I am
just hoping to get thing going by merging the patchset in its current
form and then we can make it hierarchical in a followup patch.
Cheers,
Longman
next prev parent reply other threads:[~2018-07-20 16:19 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
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 [this message]
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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