Re: [PATCH] mm: vmscan: correct nr_reclaimed for THP

[Yang Shi]

On 5/10/19 9:36 AM, Matthew Wilcox wrote:
> On Fri, May 10, 2019 at 10:12:40AM +0800, Huang, Ying wrote:
> > > +		nr_reclaimed += (1 << compound_order(page));
> > How about to change this to
> >
> >
> >          nr_reclaimed += hpage_nr_pages(page);
> Please don't.  That embeds the knowledge that we can only swap out either
> normal pages or THP sized pages.  I'm trying to make the VM capable of
> supporting arbitrary-order pages, and this would be just one more place
> to fix.
>
> I'm sympathetic to the "self documenting" argument.  My current tree has
> a patch in it:
>
>      mm: Introduce compound_nr
>      
>      Replace 1 << compound_order(page) with compound_nr(page).  Minor
>      improvements in readability.
>
> It goes along with this patch:
>
>      mm: Introduce page_size()
>
>      It's unnecessarily hard to find out the size of a potentially huge page.
>      Replace 'PAGE_SIZE << compound_order(page)' with page_size(page).

So you prefer keeping using "1 << compound_order" as v1 did? Then you 
will convert all "1 << compound_order" to compound_nr?

> Better suggestions on naming gratefully received.  I'm more happy with
> page_size() than I am with compound_nr().  page_nr() gives the wrong
> impression; page_count() isn't great either.