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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>,
	Patrick Bellasi <patrick.bellasi@arm.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: [PATCH v9 3/7] cpuset: Add cpuset.sched.load_balance flag to v2
Date: Wed, 20 Jun 2018 16:46:13 +0200	[thread overview]
Message-ID: <20180620144613.GP2476@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <54c607c3-e742-4da9-c89a-4ed54146e3bd@redhat.com>

On Thu, May 31, 2018 at 12:42:20PM -0400, Waiman Long wrote:
> Thinking about isolcpus emulation, I now realize that it is more than
> just disabling load balancing. it also disables some kernel threads like
> kworker from running so that an userspace application can monopolize as
> much of a cpu as possible. Disabling kernel threads from running isn't
> that hard if it is only done once at boot time. it is trickier if we
> have to do it at run time.

Don't think it is all that difficult, we just need a notifier for when
that housekeeping thing changes and ensure that everybody who uses it
re-evaluates crap.

> Without good isolcpus emulation, disabling load balance kind of loses
> its usefulness. So I am going to take out the load_balance flag for now
> unless I hear objection otherwise.

I'm not seeing the direct link between the load_balance flag and
isolcpus emulation in the proposed stuff.

We can tie the housekeeping mask to whatever CPUs remain in the root
cgroup, couple that to that notifier and it should all just work I
think.

WARNING: multiple messages have this Message-ID (diff)
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>,
	Patrick Bellasi <patrick.bellasi@arm.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: [PATCH v9 3/7] cpuset: Add cpuset.sched.load_balance flag to v2
Date: Wed, 20 Jun 2018 16:46:13 +0200	[thread overview]
Message-ID: <20180620144613.GP2476@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <54c607c3-e742-4da9-c89a-4ed54146e3bd@redhat.com>

On Thu, May 31, 2018 at 12:42:20PM -0400, Waiman Long wrote:
> Thinking about isolcpus emulation, I now realize that it is more than
> just disabling load balancing. it also disables some kernel threads like
> kworker from running so that an userspace application can monopolize as
> much of a cpu as possible. Disabling kernel threads from running isn't
> that hard if it is only done once at boot time. it is trickier if we
> have to do it at run time.

Don't think it is all that difficult, we just need a notifier for when
that housekeeping thing changes and ensure that everybody who uses it
re-evaluates crap.

> Without good isolcpus emulation, disabling load balance kind of loses
> its usefulness. So I am going to take out the load_balance flag for now
> unless I hear objection otherwise.

I'm not seeing the direct link between the load_balance flag and
isolcpus emulation in the proposed stuff.

We can tie the housekeeping mask to whatever CPUs remain in the root
cgroup, couple that to that notifier and it should all just work I
think.
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  reply	other threads:[~2018-06-20 14:46 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-29 13:41 [PATCH v9 0/7] Enable cpuset controller in default hierarchy Waiman Long
2018-05-29 13:41 ` Waiman Long
2018-05-29 13:41 ` [PATCH v9 1/7] cpuset: " Waiman Long
2018-05-29 13:41   ` Waiman Long
2018-05-29 13:41 ` [PATCH v9 2/7] cpuset: Add new v2 cpuset.sched.domain_root flag Waiman Long
2018-05-29 13:41   ` Waiman Long
2018-05-30 14:18   ` Juri Lelli
2018-05-30 14:18     ` Juri Lelli
2018-05-30 14:57     ` Waiman Long
2018-05-30 14:57       ` Waiman Long
2018-05-31  9:49   ` Peter Zijlstra
2018-05-31  9:49     ` Peter Zijlstra
2018-05-29 13:41 ` [PATCH v9 3/7] cpuset: Add cpuset.sched.load_balance flag to v2 Waiman Long
2018-05-29 13:41   ` Waiman Long
2018-05-31 10:44   ` Peter Zijlstra
2018-05-31 10:44     ` Peter Zijlstra
2018-05-31 10:54   ` Peter Zijlstra
2018-05-31 10:54     ` Peter Zijlstra
2018-05-31 13:36     ` Waiman Long
2018-05-31 13:36       ` Waiman Long
2018-05-31 12:26   ` Peter Zijlstra
2018-05-31 12:26     ` Peter Zijlstra
2018-05-31 13:54     ` Waiman Long
2018-05-31 13:54       ` Waiman Long
2018-05-31 15:20       ` Peter Zijlstra
2018-05-31 15:20         ` Peter Zijlstra
2018-05-31 15:36         ` Waiman Long
2018-05-31 15:36           ` Waiman Long
2018-05-31 16:08           ` Peter Zijlstra
2018-05-31 16:08             ` Peter Zijlstra
2018-05-31 16:42             ` Waiman Long
2018-05-31 16:42               ` Waiman Long
2018-06-20 14:46               ` Peter Zijlstra [this message]
2018-06-20 14:46                 ` Peter Zijlstra
2018-06-21  7:40                 ` Waiman Long
2018-06-21  7:40                   ` Waiman Long
2018-05-29 13:41 ` [PATCH v9 4/7] cpuset: Make generate_sched_domains() recognize isolated_cpus Waiman Long
2018-05-29 13:41   ` Waiman Long
2018-05-29 13:41 ` [PATCH v9 5/7] cpuset: Expose cpus.effective and mems.effective on cgroup v2 root Waiman Long
2018-05-29 13:41   ` Waiman Long
2018-05-29 13:41 ` [PATCH v9 6/7] cpuset: Don't rebuild sched domains if cpu changes in non-domain root Waiman Long
2018-05-29 13:41   ` Waiman Long
2018-05-29 13:41 ` [PATCH v9 7/7] cpuset: Allow reporting of sched domain generation info Waiman Long
2018-05-29 13:41   ` Waiman Long
2018-05-30 10:13 ` [PATCH v9 0/7] Enable cpuset controller in default hierarchy Juri Lelli
2018-05-30 10:13   ` Juri Lelli
2018-05-30 12:56   ` Waiman Long
2018-05-30 12:56     ` Waiman Long
2018-05-30 13:05     ` Juri Lelli
2018-05-30 13:05       ` Juri Lelli
2018-05-30 13:47       ` Waiman Long
2018-05-30 13:47         ` Waiman Long
2018-05-30 13:52         ` Juri Lelli
2018-05-30 13:52           ` Juri Lelli

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