# Re: \[PATCH 2/4\] mm: speed up mremap by 500x on large regions (v2)

- From: Joel Fernandes \<hidden\>
- Date: 2018-10-25 02:13:53 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2018/10/6489870
- Thread: https://ratatoskr.run/linux-alpha/2018/10/6489750/t.md

```text
On Wed, Oct 24, 2018 at 10:57:33PM +1100, Balbir Singh wrote:
[...]
> > > +		pmd_t pmd;
> > > +
> > > +		new_ptl = pmd_lockptr(mm, new_pmd);
> 
> 
> Looks like this is largely inspired by move_huge_pmd(), I guess a lot of
> the code applies, why not just reuse as much as possible? The same comments
> w.r.t mmap_sem helping protect against lock order issues applies as well.

I thought about this and when I looked into it, it seemed there are subtle
differences that make such sharing not worth it (or not possible).

 - Joel

```