Re: [RFC v2] percpu: Add a separate function to merge free areas

From: Tejun Heo
Date: Thu Dec 04 2014 - 16:19:19 EST

On Thu, Dec 04, 2014 at 03:15:27PM -0600, Christoph Lameter wrote:
> On Thu, 4 Dec 2014, Al Viro wrote:
> > ... except that somebody has not known that and took refcounts on e.g.
> > vfsmounts into percpu. With massive amounts of hilarity once docker folks
> > started to test the workloads that created/destroyed those in large amounts.
> Well, vfsmounts being a performance issue is a bit weird and unexpected.

Docker usage is pretty wide-spread now, making what used to be
siberia-cold paths hot enough to cause actual scalability issues.
Besides, we're now using percpu_ref for things like aio and cgroup
control structures which can be created and destroyed quite
frequently. I don't think we can say these are "weird" use cases


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