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From: Shrikanth Hegde <sshegde@linux.ibm.com>
To: Yury Norov <yury.norov@gmail.com>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
	peterz@infradead.org, juri.lelli@redhat.com,
	vincent.guittot@linaro.org, kprateek.nayak@amd.com,
	iii@linux.ibm.com, tglx@kernel.org, gregkh@linuxfoundation.org,
	pbonzini@redhat.com, seanjc@google.com, vschneid@redhat.com,
	huschle@linux.ibm.com, rostedt@goodmis.org,
	dietmar.eggemann@arm.com, mgorman@suse.de, bsegall@google.com,
	maddy@linux.ibm.com, srikar@linux.ibm.com, hdanton@sina.com,
	chleroy@kernel.org, vineeth@bitbyteword.org, frederic@kernel.org,
	arighi@nvidia.com, pauld@redhat.com, christian.loehle@arm.com,
	tj@kernel.org, tommaso.cucinotta@gmail.com, maz@kernel.org,
	rafael@kernel.org
Subject: Re: [PATCH v4 16/20] sched/core: Introduce default arch handling code for inc/dec preferred CPUs
Date: Thu, 18 Jun 2026 10:12:18 +0530	[thread overview]
Message-ID: <d37b770d-502d-488c-a4ec-aef8ca279c76@linux.ibm.com> (raw)
In-Reply-To: <ajNwy25WYg45AQJX@yury>



On 6/18/26 9:45 AM, Yury Norov wrote:
> On Wed, Jun 17, 2026 at 11:11:35PM +0530, Shrikanth Hegde wrote:
>> Define default handlers for high/low steal time. If arch has better
>> decision logic, may override the default implementation.
>>
>> - If the steal time higher than threshold, reduce the number of preferred
>>    CPUs by 1 core. The last core in the intersection of active and
>>    preferred CPUs will be marked as non-preferred.
>>    Ensure at least one core is left as preferred always.
>>
>> - If the steal time lower than threshold, increase the number of preferred
>>    CPUs by 1 core. First active core which is not in cpu_preferred_mask will
>>    be marked as preferred.
>>    If all cores are already set to preferred, bail out.
> 
> And the code below does nothing of that.

Agree. My bad. This changelog needs update.

>   
>> Increase/Decrease may need to modify the splicing across NUMA nodes. It is
>> being kept simple for now.
>>
>> Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>

  parent reply	other threads:[~2026-06-18  4:43 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-06-17 17:41 [PATCH v4 00/20] sched: Introduce cpu_preferred_mask and steal-driven vCPU backoff Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 01/20] sched/debug: Remove unused schedstats Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 02/20] sched/docs: Document cpu_preferred_mask and Preferred CPU concept Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 03/20] kconfig: Provide PREFERRED_CPU option Shrikanth Hegde
2026-06-18  0:51   ` Yury Norov
2026-06-18  3:44     ` Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 04/20] cpumask: Introduce cpu_preferred_mask Shrikanth Hegde
2026-06-18  1:29   ` Yury Norov
2026-06-18  3:53     ` Shrikanth Hegde
2026-06-18  8:27       ` Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 05/20] sysfs: Add preferred CPU file Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 06/20] sched/core: allow only preferred CPUs in is_cpu_allowed Shrikanth Hegde
2026-06-18  3:32   ` Yury Norov
     [not found]     ` <c4546759-b316-47e7-aa97-408e20d0f6ed@linux.ibm.com>
2026-06-18  4:49       ` Yury Norov
2026-06-18  5:14         ` Shrikanth Hegde
2026-06-18  3:49   ` K Prateek Nayak
2026-06-18  4:22     ` Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 07/20] sched/fair: Select preferred CPU at wakeup when possible Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 08/20] sched/fair: load balance only among preferred CPUs Shrikanth Hegde
2026-06-18  3:03   ` K Prateek Nayak
2026-06-18  3:54     ` Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 09/20] sched/core: Keep tick on non-preferred CPUs until tasks are out Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 10/20] sched/core: Push current task from non preferred CPU Shrikanth Hegde
2026-06-18  4:09   ` K Prateek Nayak
2026-06-18  6:05     ` Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 11/20] sched/debug: Add migration stats due to non preferred CPUs Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 12/20] sched/debug: Create debugfs folder steal monitor Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 13/20] sched/debug: Provide debugfs to enable/disable " Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 14/20] sched/core: Introduce a simple " Shrikanth Hegde
2026-06-18  4:30   ` Yury Norov
2026-06-18  4:44     ` Shrikanth Hegde
2026-06-18  5:32       ` K Prateek Nayak
2026-06-18  6:01         ` Shrikanth Hegde
2026-06-18  6:39           ` Yury Norov
2026-06-18  6:45             ` Shrikanth Hegde
2026-06-18  7:16               ` Yury Norov
2026-06-17 17:41 ` [PATCH v4 15/20] sched/core: Compute steal values at regular intervals Shrikanth Hegde
2026-06-18  4:04   ` Yury Norov
2026-06-18  5:39     ` Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 16/20] sched/core: Introduce default arch handling code for inc/dec preferred CPUs Shrikanth Hegde
     [not found]   ` <ajNwy25WYg45AQJX@yury>
2026-06-18  4:42     ` Shrikanth Hegde [this message]
2026-06-17 17:41 ` [PATCH v4 17/20] sched/core: Handle steal values and mark CPUs as preferred Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 18/20] sched/core: Mark the direction of steal values to avoid oscillations Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 19/20] sched/debug: Add debug knobs for steal monitor Shrikanth Hegde
2026-06-17 17:41 ` [PATCH v4 20/20] sched/core: Add a few check for valid CPU in inc/dec of preferred CPUs Shrikanth Hegde
2026-06-18  4:21   ` Yury Norov
2026-06-18  4:40     ` Shrikanth Hegde

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