Date: Tue, 18 Feb 2014 08:31:11 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Waiman Long <Waiman.Long@hp.com>, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Arnd Bergmann <arnd@arndb.de>,
        linux-arch@vger.kernel.org, x86@kernel.org,
        linux-kernel@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Michel Lespinasse <walken@google.com>,
        Andi Kleen <andi@firstfloor.org>, Rik van Riel <riel@redhat.com>,
        "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>
Subject: Re: [PATCH v4 0/3] qspinlock: Introducing a 4-byte queue spinlock
Message-ID: <20140218073111.GW27965@twins.programming.kicks-ass.net>
References: <1392669684-4807-1-git-send-email-Waiman.Long@hp.com>
 <53029167.4060109@zytor.com>
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On Mon, Feb 17, 2014 at 02:47:03PM -0800, H. Peter Anvin wrote:
> On 02/17/2014 12:41 PM, Waiman Long wrote:
> > v3->v4:
> >  - Remove debugging code and fix a configuration error
> >  - Simplify the qspinlock structure and streamline the code to make it
> >    perform a bit better
> >  - Add an x86 version of asm/qspinlock.h for holding x86 specific
> >    optimization.
> >  - Add an optimized x86 code path for 2 contending tasks to improve
> >    low contention performance.
> > 
> > v2->v3:
> >  - Simplify the code by using numerous mode only without an unfair option.
> >  - Use the latest smp_load_acquire()/smp_store_release() barriers.
> >  - Move the queue spinlock code to kernel/locking.
> >  - Make the use of queue spinlock the default for x86-64 without user
> >    configuration.
> >  - Additional performance tuning.
> > 
> > v1->v2:
> >  - Add some more comments to document what the code does.
> >  - Add a numerous CPU mode to support >= 16K CPUs
> >  - Add a configuration option to allow lock stealing which can further
> >    improve performance in many cases.
> >  - Enable wakeup of queue head CPU at unlock time for non-numerous
> >    CPU mode.
> > 
> > This patch set introduces a queue-based spinlock implementation that
> > can replace the default ticket spinlock without increasing the size
> > of the spinlock data structure. As a result, critical kernel data
> > structures that embed spinlock won't increase in size and breaking
> > data alignments.
> > 
> 
> This is starting to look good, so I have pulled it into
> tip:x86/spinlocks to start give it some testing mileage.

It very much needs paravirt muck before we can even consider it.
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