From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: paulmck@kernel.org
Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@meta.com, rostedt@goodmis.org,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
linux-arm-kernel@lists.infradead.org, bpf@vger.kernel.org
Subject: Re: [PATCH 17/19] srcu: Optimize SRCU-fast-updown for arm64
Date: Mon, 3 Nov 2025 14:22:00 -0500 [thread overview]
Message-ID: <98fa1a01-400b-4496-997c-1f84f33dd1ad@efficios.com> (raw)
In-Reply-To: <8a33bf08-8ca4-4fc1-9481-fff2247e5518@paulmck-laptop>
On 2025-11-03 14:17, Paul E. McKenney wrote:
[...]
>> This is effectively a use of split-counters, but the split
>> is across concurrency handling mechanisms rather than across
>> CPUs.
>
> Ah, got it, thank you! But we would need an additional softirq counter,
> correct?
Fundamentally it depends on how you want to split frequent vs infrequent
accesses.
If the fast-paths you care about are all in thread context, then you
only need to split between percpu ops vs atomic counters. The per-thread
accesses would use percpu ops, and all the rest use atomics. The "all
the rest" can cover everything else including softirqs, irq, and nmis.
>
> I will keep this in my back pocket in case Catalin's and Yicong's prefetch
> trick turns out to be problematic, and again, thank you!
You're welcome! :)
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
prev parent reply other threads:[~2025-11-03 19:22 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <082fb8ba-91b8-448e-a472-195eb7b282fd@paulmck-laptop>
2025-11-02 21:44 ` [PATCH 02/19] srcu: Create an srcu_expedite_current() function Paul E. McKenney
2025-11-02 21:44 ` [PATCH 03/19] rcutorture: Test srcu_expedite_current() Paul E. McKenney
2025-11-02 21:44 ` [PATCH 04/19] srcu: Create a DEFINE_SRCU_FAST() Paul E. McKenney
2025-11-02 21:44 ` [PATCH 05/19] srcu: Make grace-period determination use ssp->srcu_reader_flavor Paul E. McKenney
2025-11-02 21:44 ` [PATCH 06/19] rcutorture: Exercise DEFINE_STATIC_SRCU_FAST() and init_srcu_struct_fast() Paul E. McKenney
2025-11-02 21:44 ` [PATCH 07/19] srcu: Require special srcu_struct define/init for SRCU-fast readers Paul E. McKenney
2025-11-02 21:44 ` [PATCH 08/19] srcu: Make SRCU-fast readers enforce use of SRCU-fast definition/init Paul E. McKenney
2025-11-02 21:44 ` [PATCH 09/19] doc: Update for SRCU-fast definitions and initialization Paul E. McKenney
2025-11-02 21:44 ` [PATCH 10/19] tracing: Guard __DECLARE_TRACE() use of __DO_TRACE_CALL() with SRCU-fast Paul E. McKenney
2025-11-02 21:44 ` [PATCH 13/19] srcu: Add SRCU_READ_FLAVOR_FAST_UPDOWN CPP macro Paul E. McKenney
2025-11-02 21:44 ` [PATCH 15/19] srcu: Create an SRCU-fast-updown API Paul E. McKenney
2025-11-04 7:00 ` Akira Yokosawa
2025-11-04 16:49 ` Paul E. McKenney
2025-11-02 21:44 ` [PATCH 16/19] rcutorture: Test SRCU-fast separately from SRCU-fast-updown Paul E. McKenney
2025-11-02 21:44 ` [PATCH 17/19] srcu: Optimize SRCU-fast-updown for arm64 Paul E. McKenney
2025-11-03 12:51 ` Will Deacon
2025-11-03 14:07 ` Catalin Marinas
2025-11-03 17:02 ` Paul E. McKenney
2025-11-03 13:34 ` Mathieu Desnoyers
2025-11-03 17:08 ` Paul E. McKenney
2025-11-03 18:16 ` Mathieu Desnoyers
2025-11-03 19:17 ` Paul E. McKenney
2025-11-03 19:22 ` Mathieu Desnoyers [this message]
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