Re: [PATCH 10/13] x86: mm: Enable deferred struct page initialisation on x86-64

[Waiman Long]

On 04/25/2015 01:28 PM, Mel Gorman wrote:
> On Fri, Apr 24, 2015 at 03:04:27PM -0400, Waiman Long wrote:
> > > > Within a NUMA node, however, we can split the
> > > > memory initialization to 2 or more local CPUs if the memory size is
> > > > big enough.
> > > I considered it but discarded the idea. It'd be more complex to setup and
> > > the two CPUs could simply end up contending on the same memory bus as
> > > well as contending on zone->lock.
> > I don't think we need that now. However, we may have to consider
> > this when one day even a single node can have TBs of memory unless
> > we move to a page size larger than 4k.
> We'll cross that bridge when we come to it. I suspect there is more room
> for improvement in the initialisation that would be worth trying before
> resorting to more threads. With more threads there is a risk that we hit
> memory bus contention and a high risk that it actually is worse due to
> contending on zone->lock when freeing the pages.
>
> In the meantime, do you mind updating the before/after figures for your
> test machine with this series please?

I will test the latest patch once I got my hand on a 12TB machine.

Cheers,
Longman
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