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 07:54:39 +0000 [thread overview]
Message-ID: <8276AA2B-72D9-4B2A-9F50-E6C2744BB9E8@tencent.com> (raw)
In-Reply-To: <97a82444-77ab-dbd2-f765-0d818f94ca0b@linux.intel.com>
Hi,
> On Aug 14, 2020, at 1:18 PM, Li, Aubrey <aubrey.li@linux.intel.com> wrote:
>
> On 2020/8/14 12:04, benbjiang(蒋彪) wrote:
>>
>>
>>> 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?
>>
> IMHO the disadvantage is that if there are two or more cgroups set cookie-0,
> then the user applications in these cgroups could run concurrently on a core,
> though all of them are set as trusted, we made a hole of user->user isolation.
For that case, how about,
- use a special cookie(cookie-trust) instead of cookie-0 for kernel thread
- implement cookie_partial_match() to match part of the cookie
- Cookie-normal(normal tasks use) could trust cookie-trust,
- tasks tend to be trusted by cookie-trust could use cookies including
cookie-trust partially, while cookie-normal does not include cookie-trust.
- cookie-trust tasks use cookie_partial_match() to match cookie
- normal tasks use the standard cookie match(full match) interface to match cookie.
Just a sudden thought. :)
Thx.
Regards,
Jiang
next prev parent reply other threads:[~2020-08-14 7:54 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)
2020-08-14 5:18 ` Li, Aubrey
2020-08-14 7:54 ` benbjiang(蒋彪) [this message]
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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