From: K Prateek Nayak <kprateek.nayak@amd.com>
To: Shrikanth Hegde <sshegde@linux.ibm.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Valentin Schneider <vschneid@redhat.com>,
"Gautham R. Shenoy" <gautham.shenoy@amd.com>,
Swapnil Sapkal <swapnil.sapkal@amd.com>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
"Juri Lelli" <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Anna-Maria Behnsen <anna-maria@linutronix.de>,
Frederic Weisbecker <frederic@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
<linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 03/19] sched/fair: Use rq->nohz_tick_stopped in update_nohz_stats()
Date: Thu, 25 Sep 2025 07:18:48 +0530 [thread overview]
Message-ID: <7f8db11e-35f5-430d-93a7-35c0e9ec8dc7@amd.com> (raw)
In-Reply-To: <409bde01-720b-4602-bde9-a04262ea2c73@linux.ibm.com>
Hello Shrikanth,
On 9/25/2025 1:47 AM, Shrikanth Hegde wrote:
>
>
> On 9/4/25 9:44 AM, K Prateek Nayak wrote:
>> "rq->nohz_tick_stopped" always follows the state of CPU on
>> "nohz.idle_cpus_mask". Use the local rq indicator instead of checking
>> for the CPU on the "idle_cpus_mask".
>>
>> Use READ_ONCE() and WRITE_ONCE() for "rq->nohz_tick_stopped" to ensure
>> update_nohz_stats() always sees the latest value.
>>
>
> Is this ever called by remote CPU? If not, is READ/WRITE ONCE is necessary?
Patch 6 looks at "rq->nohz_tick_stopped" to correct the idle mask in the
sched domain rebuild path which is done from a remote CPU.
--
Thanks and Regards,
Prateek
next prev parent reply other threads:[~2025-09-25 1:48 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-04 4:14 [RFC PATCH 00/19] sched/fair: Distributed nohz idle CPU tracking for idle load balancing K Prateek Nayak
2025-09-04 4:14 ` [RFC PATCH 01/19] sched/fair: Simplify set_cpu_sd_state_*() with guards K Prateek Nayak
2025-09-24 20:26 ` Shrikanth Hegde
2025-09-25 2:11 ` K Prateek Nayak
2025-09-04 4:14 ` [RFC PATCH 02/19] sched/topology: Optimize sd->shared allocation and assignment K Prateek Nayak
2025-09-04 4:14 ` [RFC PATCH 03/19] sched/fair: Use rq->nohz_tick_stopped in update_nohz_stats() K Prateek Nayak
2025-09-24 20:17 ` Shrikanth Hegde
2025-09-25 1:48 ` K Prateek Nayak [this message]
2025-09-04 4:15 ` [RFC PATCH 04/19] sched/fair: Use xchg() to set sd->nohz_idle state K Prateek Nayak
2025-09-04 4:15 ` [RFC PATCH 05/19] sched/topology: Attach new hierarchy in rq_attach_root() K Prateek Nayak
2025-09-04 4:15 ` [RFC PATCH 06/19] sched/fair: Fixup sd->nohz_idle state during hotplug / cpuset K Prateek Nayak
2025-09-04 4:15 ` [RFC PATCH 07/19] sched/fair: Account idle cpus instead of busy cpus in sd->shared K Prateek Nayak
2025-09-04 4:15 ` [RFC PATCH 08/19] sched/topology: Introduce fallback sd->shared assignment K Prateek Nayak
2025-09-04 4:15 ` [RFC PATCH 09/19] sched/topology: Introduce percpu sd_nohz for nohz state tracking K Prateek Nayak
2025-09-04 4:15 ` [RFC PATCH 10/19] sched/topology: Introduce "idle_cpus_mask" in sd->shared K Prateek Nayak
2025-09-04 4:15 ` [RFC PATCH 11/19] sched/topology: Introduce "nohz_shared_list" to keep track of sd->shared K Prateek Nayak
2025-09-04 4:15 ` [RFC PATCH 12/19] sched/fair: Reorder the barrier in nohz_balance_enter_idle() K Prateek Nayak
2025-09-04 4:15 ` [RFC PATCH 13/19] sched/fair: Extract the main _nohz_idle_balance() loop into a helper K Prateek Nayak
2025-09-04 4:15 ` [RFC PATCH 14/19] sched/fair: Convert find_new_ilb() to use nohz_shared_list K Prateek Nayak
2025-09-04 4:15 ` [RFC PATCH 15/19] sched/fair: Introduce sched_asym_prefer_idle() for ILB kick K Prateek Nayak
2025-09-04 4:15 ` [RFC PATCH 16/19] sched/fair: Convert sched_balance_nohz_idle() to use nohz_shared_list K Prateek Nayak
2025-09-04 4:15 ` [RFC PATCH 17/19] sched/fair: Remove "nohz.idle_cpus_mask" K Prateek Nayak
2025-09-04 4:15 ` [RFC PATCH 18/19] sched/fair: Optimize global "nohz.nr_cpus" tracking K Prateek Nayak
2025-09-24 20:02 ` Shrikanth Hegde
2025-09-25 2:37 ` K Prateek Nayak
2025-09-04 4:15 ` [RFC PATCH 19/19] sched/topology: Add basic debug information for "nohz_shared_list" K Prateek Nayak
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