From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: linux-arch@vger.kernel.org, guohanjun@huawei.com, arnd@arndb.de,
dave.dice@oracle.com, jglauber@marvell.com, x86@kernel.org,
will.deacon@arm.com, linux@armlinux.org.uk,
linux-kernel@vger.kernel.org, mingo@redhat.com, bp@alien8.de,
hpa@zytor.com, Alex Kogan <alex.kogan@oracle.com>,
steven.sistare@oracle.com, tglx@linutronix.de,
daniel.m.jordan@oracle.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v9 3/5] locking/qspinlock: Introduce CNA into the slow path of qspinlock
Date: Thu, 23 Jan 2020 16:29:18 +0100 [thread overview]
Message-ID: <20200123152918.GD14879@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <d751a8ef-aae8-ca70-6a28-79dd8bee2324@redhat.com>
On Thu, Jan 23, 2020 at 09:15:55AM -0500, Waiman Long wrote:
> On 1/14/20 10:59 PM, Alex Kogan wrote:
> > +static int __init cna_init_nodes(void)
> > +{
> > + unsigned int cpu;
> > +
> > + /*
> > + * this will break on 32bit architectures, so we restrict
> > + * the use of CNA to 64bit only (see arch/x86/Kconfig)
> > + */
> > + BUILD_BUG_ON(sizeof(struct cna_node) > sizeof(struct qnode));
> > + /* we store an ecoded tail word in the node's @locked field */
> > + BUILD_BUG_ON(sizeof(u32) > sizeof(unsigned int));
> > +
> > + for_each_possible_cpu(cpu)
> > + cna_init_nodes_per_cpu(cpu);
> > +
> > + return 0;
> > +}
> > +early_initcall(cna_init_nodes);
> > +
>
> I just realized that you shouldn't call cna_init_nodes as an
> early_initcall. Instead,
>
> > +/*
> > + * Switch to the NUMA-friendly slow path for spinlocks when we have
> > + * multiple NUMA nodes in native environment, unless the user has
> > + * overridden this default behavior by setting the numa_spinlock flag.
> > + */
> > +void __init cna_configure_spin_lock_slowpath(void)
> > +{
> > + if ((numa_spinlock_flag == 1) ||
> > + (numa_spinlock_flag == 0 && nr_node_ids > 1 &&
> > + pv_ops.lock.queued_spin_lock_slowpath ==
> > + native_queued_spin_lock_slowpath)) {
> > + pv_ops.lock.queued_spin_lock_slowpath =
> > + __cna_queued_spin_lock_slowpath;
> > +
> > + pr_info("Enabling CNA spinlock\n");
> > + }
> > +}
>
> call it when it is sure that CNA spinlock is going to be used. At this
> point, the system is still in UP mode and the slowpath will not be called.
Indeed, let me go fix that!
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next prev parent reply other threads:[~2020-01-23 15:29 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-15 3:59 [PATCH v9 0/5] Add NUMA-awareness to qspinlock Alex Kogan
2020-01-15 3:59 ` [PATCH v9 1/5] locking/qspinlock: Rename mcs lock/unlock macros and make them more generic Alex Kogan
2020-01-15 3:59 ` [PATCH v9 2/5] locking/qspinlock: Refactor the qspinlock slow path Alex Kogan
2020-01-15 3:59 ` [PATCH v9 3/5] locking/qspinlock: Introduce CNA into the slow path of qspinlock Alex Kogan
2020-01-23 9:26 ` Peter Zijlstra
2020-01-23 10:06 ` Peter Zijlstra
2020-01-23 10:16 ` Peter Zijlstra
2020-01-23 11:22 ` Will Deacon
2020-01-23 13:17 ` Peter Zijlstra
2020-01-23 14:15 ` Waiman Long
2020-01-23 15:29 ` Peter Zijlstra [this message]
2020-01-15 3:59 ` [PATCH v9 4/5] locking/qspinlock: Introduce starvation avoidance into CNA Alex Kogan
2020-01-23 19:55 ` Waiman Long
2020-01-23 20:39 ` Waiman Long
2020-01-23 23:39 ` Alex Kogan
2020-01-15 3:59 ` [PATCH v9 5/5] locking/qspinlock: Introduce the shuffle reduction optimization " Alex Kogan
2020-01-22 11:45 ` [PATCH v9 0/5] Add NUMA-awareness to qspinlock Lihao Liang
2020-01-22 17:24 ` Waiman Long
2020-01-23 11:35 ` Will Deacon
2020-01-23 15:25 ` Waiman Long
2020-01-23 19:08 ` Waiman Long
2020-01-22 19:29 ` Alex Kogan
2020-01-26 0:32 ` Lihao Liang
2020-01-26 1:58 ` Lihao Liang
2020-01-27 16:01 ` Alex Kogan
2020-01-29 1:39 ` Lihao Liang
2020-01-27 6:16 ` Alex Kogan
2020-01-24 22:24 ` Paul E. McKenney
[not found] ` <6AAE7FC6-F5DE-4067-8BC4-77F27948CD09@oracle.com>
2020-01-25 0:57 ` Paul E. McKenney
2020-01-25 1:59 ` Waiman Long
[not found] ` <adb4fb09-f374-4d64-096b-ba9ad8b35fd5@redhat.com>
2020-01-25 4:58 ` Paul E. McKenney
2020-01-25 19:41 ` Waiman Long
2020-01-26 15:35 ` Paul E. McKenney
2020-01-26 22:42 ` Paul E. McKenney
2020-01-26 23:32 ` Paul E. McKenney
2020-01-27 6:04 ` Alex Kogan
2020-01-27 14:11 ` Waiman Long
2020-01-27 15:09 ` Paul E. McKenney
[not found] ` <9b3a3f16-5405-b6d1-d023-b85f4aab46dd@redhat.com>
2020-01-27 17:17 ` Waiman Long
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