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From: Barry Song <21cnbao@gmail.com>
To: alex.kogan@oracle.com
Cc: arnd@arndb.de, bp@alien8.de, daniel.m.jordan@oracle.com,
	dave.dice@oracle.com, guohanjun@huawei.com, hpa@zytor.com,
	jglauber@marvell.com, linux-arch@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux@armlinux.org.uk,
	longman@redhat.com, mingo@redhat.com, peterz@infradead.org,
	steven.sistare@oracle.com, tglx@linutronix.de,
	will.deacon@arm.com, x86@kernel.org
Subject: Re: [PATCH v15 3/6] locking/qspinlock: Introduce CNA into the slow path of qspinlock
Date: Thu, 30 Sep 2021 18:05:14 +0800	[thread overview]
Message-ID: <20210930100514.10121-1-21cnbao@gmail.com> (raw)
In-Reply-To: <20210514200743.3026725-4-alex.kogan@oracle.com>

> +/*
> + * Implement a NUMA-aware version of MCS (aka CNA, or compact NUMA-aware lock).
> + *
> + * In CNA, spinning threads are organized in two queues, a primary queue for
> + * threads running on the same NUMA node as the current lock holder, and a
> + * secondary queue for threads running on other nodes. Schematically, it
> + * looks like this:
> + *
> + *    cna_node
> + *   +----------+     +--------+         +--------+
> + *   |mcs:next  | --> |mcs:next| --> ... |mcs:next| --> NULL  [Primary queue]
> + *   |mcs:locked| -.  +--------+         +--------+
> + *   +----------+  |
> + *                 `----------------------.
> + *                                        v
> + *                 +--------+         +--------+
> + *                 |mcs:next| --> ... |mcs:next|            [Secondary queue]
> + *                 +--------+         +--------+
> + *                     ^                    |
> + *                     `--------------------'
> + *

probably not only related with NUMA, it might be also related with cache topology.
For example, one NUMA might has a couple of sub domains, each domain shares some
last level cache. ZEN, Power and some ARM servers all have this kind of topology.

lock synchronization within this smaller range should be much faster. anyway, it
looks like a good start to be aware of numa only for this moment.

Thanks
barry

  parent reply	other threads:[~2021-09-30 10:05 UTC|newest]

Thread overview: 14+ 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
2021-09-30 10:05   ` Barry Song [this message]
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

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