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SubjectRe: [PATCH -mm -v10 1/3] mm, THP, swap: Delay splitting THP during swap out
On Thu, May 11, 2017 at 08:25:56AM +0900, Minchan Kim wrote:
> On Wed, May 10, 2017 at 09:56:54AM -0400, Johannes Weiner wrote:
> > Hi Michan,
> >
> > On Tue, May 02, 2017 at 08:53:32AM +0900, Minchan Kim wrote:
> > > @@ -1144,7 +1144,7 @@ void swap_free(swp_entry_t entry)
> > > /*
> > > * Called after dropping swapcache to decrease refcnt to swap entries.
> > > */
> > > -void swapcache_free(swp_entry_t entry)
> > > +void __swapcache_free(swp_entry_t entry)
> > > {
> > > struct swap_info_struct *p;
> > >
> > > @@ -1156,7 +1156,7 @@ void swapcache_free(swp_entry_t entry)
> > > }
> > >
> > > #ifdef CONFIG_THP_SWAP
> > > -void swapcache_free_cluster(swp_entry_t entry)
> > > +void __swapcache_free_cluster(swp_entry_t entry)
> > > {
> > > unsigned long offset = swp_offset(entry);
> > > unsigned long idx = offset / SWAPFILE_CLUSTER;
> > > @@ -1182,6 +1182,14 @@ void swapcache_free_cluster(swp_entry_t entry)
> > > }
> > > #endif /* CONFIG_THP_SWAP */
> > >
> > > +void swapcache_free(struct page *page, swp_entry_t entry)
> > > +{
> > > + if (!PageTransHuge(page))
> > > + __swapcache_free(entry);
> > > + else
> > > + __swapcache_free_cluster(entry);
> > > +}
> >
> > I don't think this is cleaner :/

Let's see a example add_to_swap. Without it, it looks like that.

int add_to_swap(struct page *page)
{
entry = get_swap_page(page);
..
..
fail:
if (PageTransHuge(page))
swapcache_free_cluster(entry);
else
swapcache_free(entry);
}

It doesn't looks good to me because get_swap_page hides
where entry allocation is from cluster or slot but when
we free the entry allocated, we should be aware of the
internal and call right function. :(

Do you think it's better still?

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