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SubjectRe: [PATCH v2] mm: exclude isolated non-lru pages from NR_ISOLATED_ANON or NR_ISOLATED_FILE.
Hi, Michal,

On Fri, Oct 14, 2016 at 01:30:44PM +0200, Michal Hocko wrote:

< snip>

> > void putback_movable_pages(struct list_head *l)
> > {
> > ......
> > /*
> > * We isolated non-lru movable page so here we can use
> > * __PageMovable because LRU page's mapping cannot have
> > * PAGE_MAPPING_MOVABLE.
> > */
> > if (unlikely(__PageMovable(page))) {
> > VM_BUG_ON_PAGE(!PageIsolated(page), page);
> > lock_page(page);
> > if (PageMovable(page))
> > putback_movable_page(page);
> > else
> > __ClearPageIsolated(page);
> > unlock_page(page);
> > put_page(page);
> > } else {
> > putback_lru_page(page);
> > }
> > }
>
> I am not familiar with this code enough to comment but to me it all
> sounds quite subtle.

It was due to lacking of page flags on 32bit machine, sadly.
Better idea is always welcome.

>
> > > Why don't you simply mimic what shrink_inactive_list does? Aka count the
> > > number of isolated pages and then account them when appropriate?
> > >
> > I think i am correcting clearly wrong part. So, there is no need to
> > describe it too detailed. It's a misunderstanding, and i will add
> > more comments as you suggest.
>
> OK, so could you explain why you prefer to relyon __PageMovable rather
> than do a trivial counting during the isolation?

I don't get it. Could you elaborate it a bit more?

> --
> Michal Hocko
> SUSE Labs

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