From: Tejun Heo <tj@kernel.org>
To: Waiman Long <llong@redhat.com>
Cc: Frederic Weisbecker <frederic@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>,
Marco Crivellari <marco.crivellari@suse.com>,
Michal Hocko <mhocko@suse.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH 02/27] sched/isolation: Introduce housekeeping per-cpu rwsem
Date: Mon, 23 Jun 2025 08:03:46 -1000 [thread overview]
Message-ID: <aFmXAjmtasot2rp6@slm.duckdns.org> (raw)
In-Reply-To: <509c307c-c72f-423c-b5c4-a1c5fdcac7a1@redhat.com>
Hello,
On Mon, Jun 23, 2025 at 01:57:17PM -0400, Waiman Long wrote:
> The percpu-rwsem does have a cheaper read side compared with rwsem for
> typical use case where writer update happens sparingly. However, when the
> writer has successful acquired the write lock, the readers do have to wait
> until the writer issues a percpu_up_write() call before they can proceed. It
> is the delay introduced by this wait that I am worry about. Isolated
> partitions are typically set up to run RT applications that have a strict
> latency requirement. So any possible latency spike should be avoided.
I see. Hmm... this being the mechanism that establishes the isolation, it
doesn't seem too broken if things stutter a bit when isolation is being
updated. Let's see what Frederic says why the strong interlocking is needed.
Thanks.
--
tejun
next prev parent reply other threads:[~2025-06-23 18:03 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-20 15:22 [PATCH 00/27] cpuset/isolation: Honour kthreads preferred affinity Frederic Weisbecker
2025-06-20 15:22 ` [PATCH 01/27] sched/isolation: Remove housekeeping static key Frederic Weisbecker
2025-06-20 15:22 ` [PATCH 02/27] sched/isolation: Introduce housekeeping per-cpu rwsem Frederic Weisbecker
2025-06-23 17:34 ` Waiman Long
2025-06-23 17:39 ` Tejun Heo
2025-06-23 17:57 ` Waiman Long
2025-06-23 18:03 ` Tejun Heo [this message]
2025-06-25 14:30 ` Frederic Weisbecker
2025-06-25 12:18 ` Phil Auld
2025-06-25 14:34 ` Frederic Weisbecker
2025-06-25 15:50 ` Phil Auld
2025-06-27 0:11 ` Waiman Long
2025-06-27 0:48 ` Phil Auld
2025-06-30 12:59 ` Thomas Gleixner
2025-06-25 14:18 ` Frederic Weisbecker
2025-06-26 23:58 ` Waiman Long
2025-06-20 15:22 ` [PATCH 03/27] PCI: Protect against concurrent change of housekeeping cpumask Frederic Weisbecker
2025-06-20 16:17 ` Bjorn Helgaas
2025-06-26 14:51 ` Frederic Weisbecker
2025-06-20 15:22 ` [PATCH 04/27] cpu: Protect against concurrent isolated cpuset change Frederic Weisbecker
2025-06-20 15:22 ` [PATCH 05/27] memcg: Prepare to protect " Frederic Weisbecker
2025-06-20 19:19 ` Shakeel Butt
2025-06-20 15:22 ` [PATCH 06/27] mm: vmstat: " Frederic Weisbecker
2025-06-20 15:22 ` [PATCH 07/27] sched/isolation: Save boot defined domain flags Frederic Weisbecker
2025-06-20 15:22 ` [PATCH 08/27] cpuset: Convert boot_hk_cpus to use HK_TYPE_DOMAIN_BOOT Frederic Weisbecker
2025-06-20 15:22 ` [PATCH 09/27] driver core: cpu: Convert /sys/devices/system/cpu/isolated " Frederic Weisbecker
2025-06-20 15:22 ` [PATCH 10/27] net: Keep ignoring isolated cpuset change Frederic Weisbecker
2025-06-20 15:22 ` [PATCH 11/27] block: Protect against concurrent " Frederic Weisbecker
2025-06-20 15:59 ` Bart Van Assche
2025-06-26 15:03 ` Frederic Weisbecker
2025-06-23 5:46 ` Christoph Hellwig
2025-06-26 15:33 ` Frederic Weisbecker
2025-06-20 15:22 ` [PATCH 12/27] cpu: Provide lockdep check for CPU hotplug lock write-held Frederic Weisbecker
2025-06-20 15:22 ` [PATCH 13/27] cpuset: Provide lockdep check for cpuset lock held Frederic Weisbecker
2025-06-20 15:22 ` [PATCH 14/27] sched/isolation: Convert housekeeping cpumasks to rcu pointers Frederic Weisbecker
2025-06-20 15:22 ` [PATCH 15/27] cpuset: Update HK_TYPE_DOMAIN cpumask from cpuset Frederic Weisbecker
2025-06-20 15:22 ` [PATCH 16/27] sched/isolation: Flush memcg workqueues on cpuset isolated partition change Frederic Weisbecker
2025-06-20 19:30 ` Shakeel Butt
2025-06-20 15:22 ` [PATCH 17/27] sched/isolation: Flush vmstat " Frederic Weisbecker
2025-06-20 15:22 ` [PATCH 18/27] cpuset: Propagate cpuset isolation update to workqueue through housekeeping Frederic Weisbecker
2025-06-20 15:23 ` [PATCH 19/27] cpuset: Remove cpuset_cpu_is_isolated() Frederic Weisbecker
2025-06-20 15:23 ` [PATCH 20/27] sched/isolation: Remove HK_TYPE_TICK test from cpu_is_isolated() Frederic Weisbecker
2025-06-20 15:23 ` [PATCH 21/27] kthread: Refine naming of affinity related fields Frederic Weisbecker
2025-06-20 15:23 ` [PATCH 22/27] kthread: Include unbound kthreads in the managed affinity list Frederic Weisbecker
2025-06-20 15:23 ` [PATCH 23/27] kthread: Include kthreadd to " Frederic Weisbecker
2025-06-20 15:23 ` [PATCH 24/27] kthread: Rely on HK_TYPE_DOMAIN for preferred affinity management Frederic Weisbecker
2025-06-20 15:23 ` [PATCH 25/27] sched: Switch the fallback task allowed cpumask to HK_TYPE_DOMAIN Frederic Weisbecker
2025-06-20 15:23 ` [PATCH 26/27] kthread: Honour kthreads preferred affinity after cpuset changes Frederic Weisbecker
2025-06-20 15:23 ` [PATCH 27/27] kthread: Comment on the purpose and placement of kthread_affine_node() call Frederic Weisbecker
2025-06-20 16:08 ` [PATCH 00/27] cpuset/isolation: Honour kthreads preferred affinity Bjorn Helgaas
2025-06-26 14:57 ` Frederic Weisbecker
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