Re: [PATCH 4/4] thp: rewrite freeze_page()/unfreeze_page() with generic rmap walkers

[Andrew Morton]

On Wed, 3 Feb 2016 07:42:01 -0800 Dave Hansen <dave.hansen@xxxxxxxxx> wrote:

> On 02/03/2016 07:14 AM, Kirill A. Shutemov wrote:
> > But the new variant is somewhat slower. Current helpers iterates over
> > VMAs the compound page is mapped to, and then over ptes within this VMA.
> > New helpers iterates over small page, then over VMA the small page
> > mapped to, and only then find relevant pte.
> 
> The code simplification here is really attractive.  Can you quantify
> what the slowdown is?  Is it noticeable, or would it be in the noise
> during all the other stuff that happens under memory pressure?

yup.  And the "more testing is required" is a bit worrisome.  Is this
code really ready for getting pounded upon in -next?