From mboxrd@z Thu Jan  1 00:00:00 1970
From: Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH v3 1/2] qspinlock: Introducing a 4-byte queue spinlock
 implementation
Date: Thu, 30 Jan 2014 12:43:29 -0500
Message-ID: <52EA8F41.7000807@redhat.com>
References: <1390933151-1797-1-git-send-email-Waiman.Long@hp.com> <1390933151-1797-2-git-send-email-Waiman.Long@hp.com>
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To: Waiman Long <Waiman.Long@hp.com>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, Arnd Bergmann <arnd@arndb.de>
Cc: linux-arch@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>, Steven Rostedt <rostedt@goodmis.org>, Andrew Morton <akpm@linux-foundation.org>, Michel Lespinasse <walken@google.com>, Andi Kleen <andi@firstfloor.org>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, Linus Torvalds <torvalds@linux-foundation.org>, Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>, George Spelvin <linux@horizon.com>, Tim Chen <tim.c.chen@linux.intel.com>, Daniel J Blueman <daniel@numascale.com>, Alexander Fyodorov <halcy@yandex.ru>, Aswin Chandramouleeswaran <aswin@hp.com>, Scott J Norton <scott.norton@hp.com>, Thavatchai Makphaibulchoke <thavatchai.makpahibulchoke@hp.com>

On 01/28/2014 01:19 PM, Waiman Long wrote:
> This patch introduces a new queue spinlock implementation that can
> serve as an alternative to the default ticket spinlock. Compared with
> the ticket spinlock, this queue spinlock should be almost as fair as
> the ticket spinlock. It has about the same speed in single-thread and
> it can be much faster in high contention situations. Only in light to
> moderate contention where the average queue depth is around 1-2 will
> this queue spinlock be potentially a bit slower due to the higher
> slowpath overhead.
>
> This queue spinlock is especially suit to NUMA machines with a large
> number of cores as the chance of spinlock contention is much higher
> in those machines. The cost of contention is also higher because of
> slower inter-node memory traffic.

>
> Signed-off-by: Waiman Long <Waiman.Long@hp.com>

Acked-by: Rik van Riel <riel@redhat.com>