From: "benbjiang(蒋彪)" <benbjiang@tencent.com>
To: "Li, Aubrey" <aubrey.li@linux.intel.com>
Cc: Joel Fernandes <joel@joelfernandes.org>,
"viremana@linux.microsoft.com" <viremana@linux.microsoft.com>,
Nishanth Aravamudan <naravamudan@digitalocean.com>,
Julien Desfossez <jdesfossez@digitalocean.com>,
Peter Zijlstra <peterz@infradead.org>,
"Tim Chen" <tim.c.chen@linux.intel.com>,
Ingo Molnar <mingo@kernel.org>,
"Thomas Glexiner" <tglx@linutronix.de>,
Paul Turner <pjt@google.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
"Subhra Mazumdar" <subhra.mazumdar@oracle.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Kees Cook <keescook@chromium.org>, Greg Kerr <kerrnel@google.com>,
Phil Auld <pauld@redhat.com>, Aaron Lu <aaron.lwe@gmail.com>,
Aubrey Li <aubrey.intel@gmail.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>,
Vineeth Pillai <vineethrp@gmail.com>,
Chen Yu <yu.c.chen@intel.com>,
Christian Brauner <christian.brauner@ubuntu.com>,
"Ning, Hongyu" <hongyu.ning@linux.intel.com>
Subject: Re: [RFC PATCH 00/16] Core scheduling v6(Internet mail)
Date: Fri, 14 Aug 2020 04:04:09 +0000 [thread overview]
Message-ID: <18263ED7-88B3-4DED-9714-55D9D2EB69D9@tencent.com> (raw)
In-Reply-To: <89d973d1-1302-17a6-c647-ea7c538c2747@linux.intel.com>
> On Aug 14, 2020, at 9:36 AM, Li, Aubrey <aubrey.li@linux.intel.com> wrote:
>
> On 2020/8/14 8:26, benbjiang(蒋彪) wrote:
>>
>>
>>> On Aug 13, 2020, at 12:28 PM, Li, Aubrey <aubrey.li@linux.intel.com> wrote:
>>>
>>> On 2020/8/13 7:08, Joel Fernandes wrote:
>>>> On Wed, Aug 12, 2020 at 10:01:24AM +0800, Li, Aubrey wrote:
>>>>> Hi Joel,
>>>>>
>>>>> On 2020/8/10 0:44, Joel Fernandes wrote:
>>>>>> Hi Aubrey,
>>>>>>
>>>>>> Apologies for replying late as I was still looking into the details.
>>>>>>
>>>>>> On Wed, Aug 05, 2020 at 11:57:20AM +0800, Li, Aubrey wrote:
>>>>>> [...]
>>>>>>> +/*
>>>>>>> + * Core scheduling policy:
>>>>>>> + * - CORE_SCHED_DISABLED: core scheduling is disabled.
>>>>>>> + * - CORE_COOKIE_MATCH: tasks with same cookie can run
>>>>>>> + * on the same core concurrently.
>>>>>>> + * - CORE_COOKIE_TRUST: trusted task can run with kernel
>>>>>>> thread on the same core concurrently.
>>>>>>> + * - CORE_COOKIE_LONELY: tasks with cookie can run only
>>>>>>> + * with idle thread on the same core.
>>>>>>> + */
>>>>>>> +enum coresched_policy {
>>>>>>> + CORE_SCHED_DISABLED,
>>>>>>> + CORE_SCHED_COOKIE_MATCH,
>>>>>>> + CORE_SCHED_COOKIE_TRUST,
>>>>>>> + CORE_SCHED_COOKIE_LONELY,
>>>>>>> +};
>>>>>>>
>>>>>>> We can set policy to CORE_COOKIE_TRUST of uperf cgroup and fix this kind
>>>>>>> of performance regression. Not sure if this sounds attractive?
>>>>>>
>>>>>> Instead of this, I think it can be something simpler IMHO:
>>>>>>
>>>>>> 1. Consider all cookie-0 task as trusted. (Even right now, if you apply the
>>>>>> core-scheduling patchset, such tasks will share a core and sniff on each
>>>>>> other. So let us not pretend that such tasks are not trusted).
>>>>>>
>>>>>> 2. All kernel threads and idle task would have a cookie 0 (so that will cover
>>>>>> ksoftirqd reported in your original issue).
>>>>>>
>>>>>> 3. Add a config option (CONFIG_SCHED_CORE_DEFAULT_TASKS_UNTRUSTED). Default
>>>>>> enable it. Setting this option would tag all tasks that are forked from a
>>>>>> cookie-0 task with their own cookie. Later on, such tasks can be added to
>>>>>> a group. This cover's PeterZ's ask about having 'default untrusted').
>>>>>> (Users like ChromeOS that don't want to userspace system processes to be
>>>>>> tagged can disable this option so such tasks will be cookie-0).
>>>>>>
>>>>>> 4. Allow prctl/cgroup interfaces to create groups of tasks and override the
>>>>>> above behaviors.
>>>>>
>>>>> How does uperf in a cgroup work with ksoftirqd? Are you suggesting I set uperf's
>>>>> cookie to be cookie-0 via prctl?
>>>>
>>>> Yes, but let me try to understand better. There are 2 problems here I think:
>>>>
>>>> 1. ksoftirqd getting idled when HT is turned on, because uperf is sharing a
>>>> core with it: This should not be any worse than SMT OFF, because even SMT OFF
>>>> would also reduce ksoftirqd's CPU time just core sched is doing. Sure
>>>> core-scheduling adds some overhead with IPIs but such a huge drop of perf is
>>>> strange. Peter any thoughts on that?
>>>>
>>>> 2. Interface: To solve the performance problem, you are saying you want uperf
>>>> to share a core with ksoftirqd so that it is not forced into idle. Why not
>>>> just keep uperf out of the cgroup?
>>>
>>> I guess this is unacceptable for who runs their apps in container and vm.
>> IMHO, just as Joel proposed,
>> 1. Consider all cookie-0 task as trusted.
>> 2. All kernel threads and idle task would have a cookie 0
>> In that way, all tasks with cookies(including uperf in a cgroup) could run
>> concurrently with kernel threads.
>> That could be a good solution for the issue. :)
>
> From uperf point of review, it can trust cookie-0(I assume we still need
> some modifications to change cookie-match to cookie-compatible to allow
> ZERO and NONZERO run together).
>
> But from kernel thread point of review, it can NOT trust uperf, unless
> we set uperf's cookie to 0.
That’s right. :)
Could we set the cookie of cgroup where uperf lies to 0?
Thx.
Regards,
Jiang
>
> Thanks,
> -Aubrey
>
next prev parent reply other threads:[~2020-08-14 4:04 UTC|newest]
Thread overview: 81+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-30 21:32 [RFC PATCH 00/16] Core scheduling v6 Vineeth Remanan Pillai
2020-06-30 21:32 ` [RFC PATCH 01/16] sched: Wrap rq::lock access Vineeth Remanan Pillai
2020-06-30 21:32 ` [RFC PATCH 02/16] sched: Introduce sched_class::pick_task() Vineeth Remanan Pillai
2020-06-30 21:32 ` [RFC PATCH 03/16] sched: Core-wide rq->lock Vineeth Remanan Pillai
2020-06-30 21:32 ` [RFC PATCH 04/16] sched/fair: Add a few assertions Vineeth Remanan Pillai
2020-06-30 21:32 ` [RFC PATCH 05/16] sched: Basic tracking of matching tasks Vineeth Remanan Pillai
2020-07-21 14:02 ` [RFC PATCH 05/16] sched: Basic tracking of matching tasks(Internet mail) benbjiang(蒋彪)
2020-06-30 21:32 ` [RFC PATCH 06/16] sched: Add core wide task selection and scheduling Vineeth Remanan Pillai
2020-07-01 23:28 ` Joel Fernandes
2020-07-02 0:54 ` Tim Chen
2020-07-02 12:57 ` Joel Fernandes
2020-07-02 13:23 ` Joel Fernandes
2020-07-05 23:44 ` Tim Chen
2020-07-03 20:21 ` Vineeth Remanan Pillai
2020-07-06 14:09 ` Joel Fernandes
2020-07-06 14:38 ` Vineeth Remanan Pillai
2020-07-06 17:37 ` Joel Fernandes
2020-06-30 21:32 ` [RFC PATCH 07/16] sched/fair: Fix forced idle sibling starvation corner case Vineeth Remanan Pillai
2020-07-21 7:35 ` [RFC PATCH 07/16] sched/fair: Fix forced idle sibling starvation corner case(Internet mail) benbjiang(蒋彪)
2020-07-22 7:20 ` benbjiang(蒋彪)
2020-06-30 21:32 ` [RFC PATCH 08/16] sched/fair: wrapper for cfs_rq->min_vruntime Vineeth Remanan Pillai
2020-06-30 21:32 ` [RFC PATCH 09/16] sched/fair: core wide cfs task priority comparison Vineeth Remanan Pillai
2020-07-22 0:23 ` [RFC PATCH 09/16] sched/fair: core wide cfs task priority comparison(Internet mail) benbjiang(蒋彪)
2020-07-24 7:14 ` Aaron Lu
2020-07-24 12:08 ` Jiang Biao
2020-06-30 21:32 ` [RFC PATCH 10/16] sched: Trivial forced-newidle balancer Vineeth Remanan Pillai
2020-07-20 4:06 ` [RFC PATCH 10/16] sched: Trivial forced-newidle balancer(Internet mail) benbjiang(蒋彪)
2020-07-20 6:06 ` Li, Aubrey
[not found] ` <8082F052-2F52-42D3-B396-18A35A94F26F@tencent.com>
2020-07-20 8:03 ` Li, Aubrey
2020-07-20 8:22 ` benbjiang(蒋彪)
2020-07-20 14:34 ` benbjiang(蒋彪)
2020-06-30 21:32 ` [RFC PATCH 11/16] sched: migration changes for core scheduling Vineeth Remanan Pillai
2020-07-22 8:54 ` [RFC PATCH 11/16] sched: migration changes for core scheduling(Internet mail) benbjiang(蒋彪)
2020-07-22 12:13 ` Li, Aubrey
2020-07-22 14:32 ` benbjiang(蒋彪)
2020-07-23 1:57 ` Li, Aubrey
2020-07-23 2:42 ` benbjiang(蒋彪)
2020-07-23 3:35 ` Li, Aubrey
2020-07-23 4:23 ` benbjiang(蒋彪)
2020-07-23 5:39 ` Li, Aubrey
2020-07-23 7:47 ` benbjiang(蒋彪)
2020-07-23 8:06 ` Li, Aubrey
2020-07-23 8:28 ` benbjiang(蒋彪)
2020-07-23 23:43 ` Aubrey Li
2020-07-24 1:26 ` benbjiang(蒋彪)
2020-07-24 2:05 ` Li, Aubrey
2020-07-24 2:29 ` benbjiang(蒋彪)
2020-06-30 21:32 ` [RFC PATCH 12/16] sched: cgroup tagging interface for core scheduling Vineeth Remanan Pillai
2020-06-30 21:32 ` [RFC PATCH 13/16] sched: Fix pick_next_task() race condition in " Vineeth Remanan Pillai
2020-06-30 21:32 ` [RFC PATCH 14/16] irq: Add support for core-wide protection of IRQ and softirq Vineeth Remanan Pillai
2020-07-10 12:19 ` Li, Aubrey
2020-07-10 13:21 ` Joel Fernandes
2020-07-13 2:23 ` Li, Aubrey
2020-07-13 15:58 ` Joel Fernandes
2020-07-10 13:36 ` Vineeth Remanan Pillai
2020-07-11 1:33 ` Aubrey Li
2020-07-17 23:37 ` Thomas Gleixner
2020-07-18 17:05 ` Joel Fernandes
2020-07-17 23:36 ` Thomas Gleixner
2020-07-20 3:53 ` Joel Fernandes
2020-07-20 8:20 ` Thomas Gleixner
2020-07-20 11:09 ` Vineeth Pillai
2020-06-30 21:32 ` [RFC PATCH 15/16] Documentation: Add documentation on core scheduling Vineeth Remanan Pillai
2020-06-30 21:32 ` [RFC PATCH 16/16] sched: Debug bits Vineeth Remanan Pillai
2020-07-31 16:41 ` [RFC PATCH 00/16] Core scheduling v6 Vineeth Pillai
2020-08-03 8:23 ` Li, Aubrey
2020-08-03 16:53 ` Joel Fernandes
2020-08-05 3:57 ` Li, Aubrey
2020-08-05 6:16 ` [RFC PATCH 00/16] Core scheduling v6(Internet mail) benbjiang(蒋彪)
2020-08-09 16:44 ` [RFC PATCH 00/16] Core scheduling v6 Joel Fernandes
2020-08-12 2:01 ` Li, Aubrey
2020-08-12 23:08 ` Joel Fernandes
2020-08-13 4:28 ` Li, Aubrey
2020-08-14 0:26 ` [RFC PATCH 00/16] Core scheduling v6(Internet mail) benbjiang(蒋彪)
2020-08-14 1:36 ` Li, Aubrey
2020-08-14 4:04 ` benbjiang(蒋彪) [this message]
2020-08-14 5:18 ` Li, Aubrey
2020-08-14 7:54 ` benbjiang(蒋彪)
2020-08-20 22:37 ` [RFC PATCH 00/16] Core scheduling v6 Joel Fernandes
2020-08-27 0:30 ` Alexander Graf
2020-08-27 1:20 ` Vineeth Pillai
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