Re: [PATCH v3 1/2] qspinlock: Introducing a 4-byte queue spinlock implementation

[Waiman Long <waiman.long@hp.com>]

On 01/30/2014 02:35 PM, Peter Zijlstra wrote:
> On Tue, Jan 28, 2014 at 01:19:10PM -0500, 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.
> But light to moderate contention should be the most common case. If your
> spinlock is very heavily contended, it should be broken up.
>
> I would really like more performance numbers for this on single and dual
> socket machines and 'normal' workloads (ha! as if those exist), ie.
> kbuild is all very important to us :-)

Yes, I am planning to get more performance data on low end machines. The 
v3 patch was sent out to spur discussion on this topic while I am trying 
to get more data.

-Longman