From: Tejun Heo <tj@kernel.org>
To: Waiman Long <longman@redhat.com>
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 v10 2/9] cpuset: Add new v2 cpuset.sched.domain_root flag
Date: Mon, 2 Jul 2018 09:32:25 -0700 [thread overview]
Message-ID: <20180702163225.GH533219@devbig577.frc2.facebook.com> (raw)
In-Reply-To: <1eb82b46-aa97-2ada-5196-5d7fc1cda87d@redhat.com>
Hello,
On Fri, Jun 22, 2018 at 11:00:03AM +0800, Waiman Long wrote:
> On 06/21/2018 05:20 PM, Peter Zijlstra wrote:
> >> As for the inconsistency between the real root and the container root,
> >> this is true for almost all the controllers. So it is a generic problem.
> >> One possible solution is to create a kind a pseudo root cgroup for the
> >> container that looks and feels like a real root. But is there really a
> >> need to do that?
> > I don't really know. I thought the idea was to make containers
> > indistinguishable from a real system. Now I know we're really rather far
> > away from that in reality, and I really have no clue how important all
> > that is.
>
> That will certainly be the ideal.
Sure, ideal in theoretical sense; however, the practical cost-benefit
ratio of trying to make containers indistinguishible from system
doesn't seem enough to justify the effort. Not yet anyway. It'd be
nice to not paint ourselves into a corner where we can't get the
equivalence without major interface changes later but I think that's
about the extent we should go for now.
> > It all depends on how exactly this works; is it like I assumed, that
> > this file is owned by the parent instead of the current directory? And
> > that if you namespace this, you have an effective read-only file?
>
> Yes, that is right.
>
> > Then fixing the inconsistency is trivial; simply provide a read-only
> > file for the actual root cgroup too.
> >
> > And if the solution is trivial, I don't see a good reason not to do it.
>
> Do you mean providing a flag like READONLY_AT_ROOT so that it will be
> read-only at the real root? That is an cgroup architectural decision
> that needs input from Tejun. Anyway, this issue is not specific to this
> patchset and I would like to break it out as a separate discussion
> independent of this patchset.
Yeah, it's a larger problem than cpuset and different controllers
trying it in different ways isn't a good idea anyway. Let's shelve
this topic for now.
Thanks.
--
tejun
next prev parent reply other threads:[~2018-07-02 16:32 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-18 4:13 [PATCH v10 0/9] cpuset: Enable cpuset controller in default hierarchy Waiman Long
2018-06-18 4:14 ` [PATCH v10 1/9] " Waiman Long
2018-06-18 4:14 ` [PATCH v10 2/9] cpuset: Add new v2 cpuset.sched.domain_root flag Waiman Long
2018-06-20 14:27 ` Peter Zijlstra
2018-06-21 7:58 ` Waiman Long
2018-06-21 8:05 ` Waiman Long
2018-06-21 9:20 ` Peter Zijlstra
2018-06-22 3:00 ` Waiman Long
2018-07-02 16:32 ` Tejun Heo [this message]
2018-06-21 9:27 ` Peter Zijlstra
2018-06-22 2:48 ` Waiman Long
2018-06-18 4:14 ` [PATCH v10 3/9] cpuset: Simulate auto-off of sched.domain_root at cgroup removal Waiman Long
2018-06-20 14:11 ` Peter Zijlstra
2018-06-21 8:22 ` Waiman Long
2018-06-18 4:14 ` [PATCH v10 4/9] cpuset: Allow changes to cpus in a domain root Waiman Long
2018-06-18 4:14 ` [PATCH v10 5/9] cpuset: Make sure that domain roots work properly with CPU hotplug Waiman Long
2018-06-20 14:15 ` Peter Zijlstra
2018-06-21 3:09 ` Waiman Long
2018-06-18 4:14 ` [PATCH v10 6/9] cpuset: Make generate_sched_domains() recognize isolated_cpus Waiman Long
2018-06-18 14:44 ` Waiman Long
2018-06-18 14:58 ` Juri Lelli
2018-06-18 4:14 ` [PATCH v10 6/9] cpuset: Make generate_sched_domains() recognize reserved_cpus Waiman Long
2018-06-20 14:17 ` Peter Zijlstra
2018-06-21 8:14 ` Waiman Long
2018-06-18 4:14 ` [PATCH v10 7/9] cpuset: Expose cpus.effective and mems.effective on cgroup v2 root Waiman Long
2018-06-18 4:14 ` [PATCH v10 8/9] cpuset: Don't rebuild sched domains if cpu changes in non-domain root Waiman Long
2018-06-18 4:14 ` [PATCH v10 9/9] cpuset: Allow reporting of sched domain generation info Waiman Long
2018-06-20 14:20 ` Peter Zijlstra
2018-06-18 14:20 ` [PATCH v10 0/9] cpuset: Enable cpuset controller in default hierarchy Juri Lelli
2018-06-18 15:07 ` Waiman Long
2018-06-19 9:52 ` Juri Lelli
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