Re: [PATCHv2 15/28] thp: handle file COW faults

[Kirill A. Shutemov]

On Fri, Feb 12, 2016 at 10:36:25AM -0800, Dave Hansen wrote:
> On 02/11/2016 06:21 AM, Kirill A. Shutemov wrote:
> > File COW for THP is handled on pte level: just split the pmd.
> 
> More changelog.  More comments, please.

Okay, I'll add more.

> We don't want to COW THP's because we'll waste memory?  A COW that we
> could handle with 4k, we would have to handle with 2M, and that's
> inefficient and high-latency?

All of above.i

It's not clear how benefitial THP file COW mappings. And it would require
some code to make them work.

I think at some point we can consider teaching khugepaged to collapse such
pages, but allocating huge on fault is probably overkill.

> Seems like a good idea to me.  It would just be nice to ensure every
> reviewer doesn't have to think their way through it.

-- 
 Kirill A. Shutemov