From: Peter Zijlstra <peterz@infradead.org>
To: Guo Ren <guoren@kernel.org>
Cc: Alex Kogan <alex.kogan@oracle.com>,
linux@armlinux.org.uk, mingo@redhat.com, will.deacon@arm.com,
arnd@arndb.de, longman@redhat.com, linux-arch@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, tglx@linutronix.de, bp@alien8.de,
hpa@zytor.com, x86@kernel.org, guohanjun@huawei.com,
jglauber@marvell.com, steven.sistare@oracle.com,
daniel.m.jordan@oracle.com, dave.dice@oracle.com
Subject: Re: [PATCH v15 3/6] locking/qspinlock: Introduce CNA into the slow path of qspinlock
Date: Fri, 4 Aug 2023 20:23:12 +0200 [thread overview]
Message-ID: <20230804182312.GO212435@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAJF2gTQ77R1embGm4kR5THcYnzk0zOJ9LOn1z=z2g7FuFN239g@mail.gmail.com>
On Fri, Aug 04, 2023 at 10:17:35AM -0400, Guo Ren wrote:
> > See, this is where the ARM64 WFE would come in handy; I don't suppose
> > RISC-V has anything like that?
> Em... arm64 smp_cond_load only could save power consumption or release
> the pipeline resources of an SMT processor. When (Node1 cpu64) is in
> the WFE state, it still needs (Node0 cpu1) to write the value to give
> a cross-NUMA signal. So I didn't see what WFE related to reducing
> cross-Numa transactions, or I missed something. Sorry
The benefit is that WFE significantly reduces the memory traffic. Since
it 'suspends' the core and waits for a write-notification instead of
busy polling the memory location you get a ton less loads.
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next prev parent reply other threads:[~2023-08-04 18:23 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-14 20:07 [PATCH v15 0/6] Add NUMA-awareness to qspinlock Alex Kogan
2021-05-14 20:07 ` [PATCH v15 1/6] locking/qspinlock: Rename mcs lock/unlock macros and make them more generic Alex Kogan
2021-05-14 20:07 ` [PATCH v15 2/6] locking/qspinlock: Refactor the qspinlock slow path Alex Kogan
2021-05-14 20:07 ` [PATCH v15 3/6] locking/qspinlock: Introduce CNA into the slow path of qspinlock Alex Kogan
2021-09-22 19:25 ` Davidlohr Bueso
2021-09-22 19:52 ` Waiman Long
2023-08-04 1:49 ` Guo Ren
2021-09-30 10:05 ` Barry Song
2023-08-02 23:14 ` Guo Ren
2023-08-03 8:50 ` Peter Zijlstra
2023-08-03 10:28 ` Guo Ren
2023-08-03 11:56 ` Peter Zijlstra
2023-08-04 1:33 ` Guo Ren
2023-08-04 1:38 ` Guo Ren
2023-08-04 8:25 ` Peter Zijlstra
2023-08-04 14:17 ` Guo Ren
2023-08-04 18:23 ` Peter Zijlstra [this message]
2023-08-05 0:19 ` Guo Ren
2021-05-14 20:07 ` [PATCH v15 4/6] locking/qspinlock: Introduce starvation avoidance into CNA Alex Kogan
2021-05-14 20:07 ` [PATCH v15 5/6] locking/qspinlock: Avoid moving certain threads between waiting queues in CNA Alex Kogan
2021-05-14 20:07 ` [PATCH v15 6/6] locking/qspinlock: Introduce the shuffle reduction optimization into CNA Alex Kogan
2021-09-30 9:44 ` [PATCH v15 0/6] Add NUMA-awareness to qspinlock Barry Song
2021-09-30 16:58 ` Waiman Long
2021-09-30 22:57 ` Barry Song
2021-09-30 23:51 ` Alex Kogan
2021-12-13 20:37 ` Alex Kogan
2021-12-15 15:13 ` Alex Kogan
2022-04-11 17:09 ` Alex Kogan
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