From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: Tejun Heo <tj@kernel.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>
Subject: Re: [PATCH v8 3/6] cpuset: Add cpuset.sched.load_balance flag to v2
Date: Mon, 28 May 2018 14:45:08 +0200 [thread overview]
Message-ID: <20180528124508.GE3452@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <9f547771-54e8-118e-80f7-48f99c7b0a12@redhat.com>
On Thu, May 24, 2018 at 02:55:25PM -0400, Waiman Long wrote:
> On 05/24/2018 11:43 AM, Peter Zijlstra wrote:
> > I'm confused... why exactly do we have both domain and load_balance ?
>
> The domain is for partitioning the CPUs only. It doesn't change the load
> balancing state. So the load_balance flag is still need to turn on and
> off load balancing.
OK, so we have to two boolean flags, giving 4 possible states. Lets just
go through them one by on:
A) domain:0 load_balance:0 -- we have no exclusive domain, but have
load-balancing disabled across them. AFAICT this should be an invalid
state.
B) domain:0 load_balance:1 -- we have no exclusive domain, but have
load-balancing enabled. AFAICT this is the default state and is a
no-op.
C) domain:1 load_balance:0 -- we have an exclusive domain, and have
load-balancing disabled across it. This is, AFAICT, identical to
having a bunch of sub/sibling groups each with a single CPU domain.
D) domain:1 load_balance:1 -- we have an exclusive domain, and have
load-balancing enabled. This is a partition.
Now, I think I've overlooked the fact that load_balance==1 only really
means something when the parent's load_balance==0, but I'm not sure that
really changes anything.
So, afaict, the above only have two useful states: B and D. Which again
raises the question, why two knobs? What useful configurations does it
allow?
next prev parent reply other threads:[~2018-05-28 12:45 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-17 20:55 [PATCH v8 0/6] Enable cpuset controller in default hierarchy Waiman Long
2018-05-17 20:55 ` [PATCH v8 1/6] cpuset: " Waiman Long
2018-05-21 11:55 ` Patrick Bellasi
2018-05-21 13:55 ` Waiman Long
2018-05-21 15:09 ` Patrick Bellasi
2018-05-21 16:10 ` Waiman Long
2018-05-17 20:55 ` [PATCH v8 2/6] cpuset: Add new v2 cpuset.sched.domain flag Waiman Long
2018-05-22 12:57 ` Juri Lelli
2018-05-22 13:20 ` Waiman Long
2018-05-29 0:55 ` Waiman Long
2018-05-24 15:41 ` Peter Zijlstra
2018-05-24 18:53 ` Waiman Long
2018-05-25 7:15 ` Peter Zijlstra
2018-05-17 20:55 ` [PATCH v8 3/6] cpuset: Add cpuset.sched.load_balance flag to v2 Waiman Long
2018-05-24 14:36 ` Juri Lelli
2018-05-24 15:09 ` Waiman Long
2018-05-24 15:16 ` Juri Lelli
2018-05-24 15:22 ` Waiman Long
2018-05-25 9:40 ` Patrick Bellasi
2018-05-25 14:45 ` Waiman Long
2018-05-24 15:43 ` Peter Zijlstra
2018-05-24 18:55 ` Waiman Long
2018-05-28 12:45 ` Peter Zijlstra [this message]
2018-05-28 18:31 ` Waiman Long
2018-05-17 20:55 ` [PATCH v8 4/6] cpuset: Make generate_sched_domains() recognize isolated_cpus Waiman Long
2018-05-23 17:34 ` Patrick Bellasi
2018-05-23 20:18 ` Waiman Long
2018-05-24 9:04 ` Patrick Bellasi
2018-05-24 10:39 ` Juri Lelli
2018-05-25 10:31 ` Patrick Bellasi
2018-05-25 12:52 ` Juri Lelli
2018-05-24 10:28 ` Juri Lelli
2018-05-29 1:12 ` Waiman Long
2018-05-29 1:24 ` Waiman Long
2018-05-29 6:27 ` Juri Lelli
2018-05-29 12:40 ` Waiman Long
2018-05-29 13:12 ` Juri Lelli
2018-05-17 20:55 ` [PATCH v8 5/6] cpuset: Expose cpus.effective and mems.effective on cgroup v2 root Waiman Long
2018-05-17 20:55 ` [PATCH v8 6/6] cpuset: Allow reporting of sched domain generation info Waiman Long
2018-05-22 13:53 ` Juri Lelli
2018-05-29 1:04 ` Waiman Long
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