Re: [PATCH v4 0/3] qspinlock: Introducing a 4-byte queue spinlock

[Peter Zijlstra]

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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