Re: [PATCH RFC 1/1] numa: fix /proc/<pid>/numa_maps for THP

[Gerald Schaefer]

On Fri, 5 Feb 2016 07:38:09 -0800
Dave Hansen <dave.hansen@xxxxxxxxx> wrote:

> On 02/05/2016 07:34 AM, Gerald Schaefer wrote:
> > +static struct page *can_gather_numa_stats_pmd(pmd_t pmd,
> > +					      struct vm_area_struct *vma,
> > +					      unsigned long addr)
> > +{
> 
> Is there a way to do this without making a copy of most of
> can_gather_numa_stats()?  Seems like the kind of thing where the pmd
> version will bitrot.
> 

Yes, that also gave me a little headache, even more with the vm_normal_page()
code duplication, but I didn't see a much better way. Separate _pte/_pmd
functions that largely do the same thing seem not so uncommon to me.

The best I could think of would be splitting the !HAVE_PTE_SPECIAL path
in vm_normal_page() into a separate function, but I see not much room for
improvement for can_gather_numa_stats(), other than maybe not having
a _pmd version at all and doing all the work inside gather_pte_stats(),
but that would probably just relocate the code duplication.