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From: Peter Zijlstra <peterz@infradead.org>
To: "Joel Fernandes (Google)" <joel@joelfernandes.org>
Cc: Nishanth Aravamudan <naravamudan@digitalocean.com>,
	Julien Desfossez <jdesfossez@digitalocean.com>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	mingo@kernel.org, tglx@linutronix.de, pjt@google.com,
	torvalds@linux-foundation.org, vpillai <vpillai@digitalocean.com>,
	linux-kernel@vger.kernel.org, fweisbec@gmail.com,
	keescook@chromium.org, kerrnel@google.com,
	Phil Auld <pauld@redhat.com>, Aaron Lu <aaron.lwe@gmail.com>,
	Aubrey Li <aubrey.intel@gmail.com>,
	aubrey.li@linux.intel.com,
	Valentin Schneider <valentin.schneider@arm.com>,
	Mel Gorman <mgorman@techsingularity.net>,
	Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Joel Fernandes <joelaf@google.com>
Subject: Re: [PATCH RFC] sched: Add a per-thread core scheduling interface
Date: Thu, 21 May 2020 10:51:22 +0200	[thread overview]
Message-ID: <20200521085122.GF325280@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200520222642.70679-1-joel@joelfernandes.org>

On Wed, May 20, 2020 at 06:26:42PM -0400, Joel Fernandes (Google) wrote:
> Add a per-thread core scheduling interface which allows a thread to tag
> itself and enable core scheduling. Based on discussion at OSPM with
> maintainers, we propose a prctl(2) interface accepting values of 0 or 1.
>  1 - enable core scheduling for the task.
>  0 - disable core scheduling for the task.

Yeah, so this is a terrible interface :-)

It doens't allow tasks for form their own groups (by for example setting
the key to that of another task).

It is also horribly ill defined what it means to 'enable', with whoem
is it allows to share a core.

> Special cases:

> (1)
> The core-scheduling patchset contains a CGroup interface as well. In
> order for us to respect users of that interface, we avoid overriding the
> tag if a task was CGroup-tagged because the task becomes inconsistent
> with the CGroup tag. Instead return -EBUSY.
> 
> (2)
> If a task is prctl-tagged, allow the CGroup interface to override
> the task's tag.

OK, so cgroup always wins; is why is that a good thing?

> ChromeOS will use core-scheduling to securely enable hyperthreading.
> This cuts down the keypress latency in Google docs from 150ms to 50ms
> while improving the camera streaming frame rate by ~3%.

It doesn't consider permissions.

Basically, with the way you guys use it, it should be a CAP_SYS_ADMIN
only to enable core-sched.

That also means we should very much default to disable.

  parent reply	other threads:[~2020-05-21  8:51 UTC|newest]

Thread overview: 115+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-04 16:59 [RFC PATCH 00/13] Core scheduling v5 vpillai
2020-03-04 16:59 ` [RFC PATCH 01/13] sched: Wrap rq::lock access vpillai
2020-03-04 16:59 ` [RFC PATCH 02/13] sched: Introduce sched_class::pick_task() vpillai
2020-03-04 16:59 ` [RFC PATCH 03/13] sched: Core-wide rq->lock vpillai
2020-04-01 11:42   ` [PATCH] sched/arm64: store cpu topology before notify_cpu_starting Cheng Jian
2020-04-01 13:23     ` Valentin Schneider
2020-04-01 13:23       ` Valentin Schneider
2020-04-06  8:00       ` chengjian (D)
2020-04-06  8:00         ` chengjian (D)
2020-04-09  9:59       ` Sudeep Holla
2020-04-09  9:59         ` Sudeep Holla
2020-04-09 10:32         ` Valentin Schneider
2020-04-09 10:32           ` Valentin Schneider
2020-04-09 11:08           ` Sudeep Holla
2020-04-09 11:08             ` Sudeep Holla
2020-04-09 17:54     ` Joel Fernandes
2020-04-10 13:49       ` chengjian (D)
2020-04-14 11:36   ` [RFC PATCH 03/13] sched: Core-wide rq->lock Peter Zijlstra
2020-04-14 21:35     ` Vineeth Remanan Pillai
2020-04-15 10:55       ` Peter Zijlstra
2020-04-14 14:32   ` Peter Zijlstra
2020-03-04 16:59 ` [RFC PATCH 04/13] sched/fair: Add a few assertions vpillai
2020-03-04 16:59 ` [RFC PATCH 05/13] sched: Basic tracking of matching tasks vpillai
2020-03-04 16:59 ` [RFC PATCH 06/13] sched: Update core scheduler queue when taking cpu online/offline vpillai
2020-03-04 16:59 ` [RFC PATCH 07/13] sched: Add core wide task selection and scheduling vpillai
2020-04-14 13:35   ` Peter Zijlstra
2020-04-16 23:32     ` Tim Chen
2020-04-17 10:57       ` Peter Zijlstra
2020-04-16  3:39   ` Chen Yu
2020-04-16 19:59     ` Vineeth Remanan Pillai
2020-04-17 11:18     ` Peter Zijlstra
2020-04-19 15:31       ` Chen Yu
2020-05-21 23:14   ` Joel Fernandes
2020-05-21 23:16     ` Joel Fernandes
2020-05-22  2:35     ` Joel Fernandes
2020-05-22  3:44       ` Aaron Lu
2020-05-22 20:13         ` Joel Fernandes
2020-03-04 16:59 ` [RFC PATCH 08/13] sched/fair: wrapper for cfs_rq->min_vruntime vpillai
2020-03-04 16:59 ` [RFC PATCH 09/13] sched/fair: core wide vruntime comparison vpillai
2020-04-14 13:56   ` Peter Zijlstra
2020-04-15  3:34     ` Aaron Lu
2020-04-15  4:07       ` Aaron Lu
2020-04-15 21:24         ` Vineeth Remanan Pillai
2020-04-17  9:40           ` Aaron Lu
2020-04-20  8:07             ` [PATCH updated] sched/fair: core wide cfs task priority comparison Aaron Lu
2020-04-20 22:26               ` Vineeth Remanan Pillai
2020-04-21  2:51                 ` Aaron Lu
2020-04-24 14:24                   ` [PATCH updated v2] " Aaron Lu
2020-05-06 14:35                     ` Peter Zijlstra
2020-05-08  8:44                       ` Aaron Lu
2020-05-08  9:09                         ` Peter Zijlstra
2020-05-08 12:34                           ` Aaron Lu
2020-05-14 13:02                             ` Peter Zijlstra
2020-05-14 22:51                               ` Vineeth Remanan Pillai
2020-05-15 10:38                                 ` Peter Zijlstra
2020-05-15 10:43                                   ` Peter Zijlstra
2020-05-15 14:24                                   ` Vineeth Remanan Pillai
2020-05-16  3:42                               ` Aaron Lu
2020-05-22  9:40                                 ` Aaron Lu
2020-06-08  1:41                               ` Ning, Hongyu
2020-03-04 17:00 ` [RFC PATCH 10/13] sched: Trivial forced-newidle balancer vpillai
2020-03-04 17:00 ` [RFC PATCH 11/13] sched: migration changes for core scheduling vpillai
2020-06-12 13:21   ` Joel Fernandes
2020-06-12 21:32     ` Vineeth Remanan Pillai
2020-06-13  2:25       ` Joel Fernandes
2020-06-13 18:59         ` Vineeth Remanan Pillai
2020-06-15  2:05           ` Li, Aubrey
2020-03-04 17:00 ` [RFC PATCH 12/13] sched: cgroup tagging interface " vpillai
2020-06-26 15:06   ` Vineeth Remanan Pillai
2020-03-04 17:00 ` [RFC PATCH 13/13] sched: Debug bits vpillai
2020-03-04 17:36 ` [RFC PATCH 00/13] Core scheduling v5 Tim Chen
2020-03-04 17:42   ` Vineeth Remanan Pillai
2020-04-14 14:21 ` Peter Zijlstra
2020-04-15 16:32   ` Joel Fernandes
2020-04-17 11:12     ` Peter Zijlstra
2020-04-17 12:35       ` Alexander Graf
2020-04-17 13:08         ` Peter Zijlstra
2020-04-18  2:25       ` Joel Fernandes
2020-05-09 14:35   ` Dario Faggioli
     [not found] ` <38805656-2e2f-222a-c083-692f4b113313@linux.intel.com>
2020-05-09  3:39   ` Ning, Hongyu
2020-05-14 20:51     ` FW: " Gruza, Agata
2020-05-10 23:46 ` [PATCH RFC] Add support for core-wide protection of IRQ and softirq Joel Fernandes (Google)
2020-05-11 13:49   ` Peter Zijlstra
2020-05-11 14:54     ` Joel Fernandes
2020-05-20 22:26 ` [PATCH RFC] sched: Add a per-thread core scheduling interface Joel Fernandes (Google)
2020-05-21  4:09   ` [PATCH RFC] sched: Add a per-thread core scheduling interface(Internet mail) benbjiang(蒋彪)
2020-05-21 13:49     ` Joel Fernandes
2020-05-21  8:51   ` Peter Zijlstra [this message]
2020-05-21 13:47     ` [PATCH RFC] sched: Add a per-thread core scheduling interface Joel Fernandes
2020-05-21 20:20       ` Vineeth Remanan Pillai
2020-05-22 12:59       ` Peter Zijlstra
2020-05-22 21:35         ` Joel Fernandes
2020-05-24 14:00           ` Phil Auld
2020-05-28 14:51             ` Joel Fernandes
2020-05-28 17:01             ` Peter Zijlstra
2020-05-28 18:17               ` Phil Auld
2020-05-28 18:34                 ` Phil Auld
2020-05-28 18:23               ` Joel Fernandes
2020-05-21 18:31   ` Linus Torvalds
2020-05-21 20:40     ` Joel Fernandes
2020-05-21 21:58       ` Jesse Barnes
2020-05-22 16:33         ` Linus Torvalds
2020-05-20 22:37 ` [PATCH RFC v2] Add support for core-wide protection of IRQ and softirq Joel Fernandes (Google)
2020-05-20 22:48 ` [PATCH RFC] sched: Use sched-RCU in core-scheduling balancing logic Joel Fernandes (Google)
2020-05-21 22:52   ` Paul E. McKenney
2020-05-22  1:26     ` Joel Fernandes
2020-06-25 20:12 ` [RFC PATCH 00/13] Core scheduling v5 Vineeth Remanan Pillai
2020-06-26  1:47   ` Joel Fernandes
2020-06-26 14:36     ` Vineeth Remanan Pillai
2020-06-26 15:10       ` Joel Fernandes
2020-06-26 15:12         ` Joel Fernandes
2020-06-27 16:21         ` Joel Fernandes
2020-06-30 14:11         ` Phil Auld
2020-06-29 12:33   ` Li, Aubrey
2020-06-29 19:41     ` Vineeth Remanan Pillai

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