On Tue, Jan 24, 2017 at 02:55:13PM -0800, Andrew Morton wrote:
> On Wed, 25 Jan 2017 01:50:30 +0300 "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> wrote:
>
> > > > + * @pcw->ptl is unlocked and @pcw->pte is unmapped.
> > > > + *
> > > > + * If you need to stop the walk before page_check_walk() returned false, use
> > > > + * page_check_walk_done(). It will do the housekeeping.
> > > > + */
> > > > +static inline bool page_check_walk(struct page_check_walk *pcw)
> > > > +{
> > > > + /* The only possible pmd mapping has been handled on last iteration */
> > > > + if (pcw->pmd && !pcw->pte) {
> > > > + page_check_walk_done(pcw);
> > > > + return false;
> > > > + }
> > > > +
> > > > + /* Only for THP, seek to next pte entry makes sense */
> > > > + if (pcw->pte) {
> > > > + if (!PageTransHuge(pcw->page) || PageHuge(pcw->page)) {
> > > > + page_check_walk_done(pcw);
> > > > + return false;
> > > > + }
> > > > + }
> > > > +
> > > > + return __page_check_walk(pcw);
> > > > +}
> > >
> > > Was the decision to inline this a correct one?
> >
> > Well, my logic was that in most cases we would have exactly one iteration.
> > The only case when we need more than one iteration is PTE-mapped THP which
> > is rare.
> > I hoped to avoid additional function call. Not sure if it worth it.
> >
> > Should I move it inside the function?
>
> I suggest building a kernel with it uninlined, take a look at the bloat
> factor then make a seat-of-the pants decision about "is it worth it".
> With quite a few callsites the saving from uninlining may be
> significant.
add/remove: 1/2 grow/shrink: 8/0 up/down: 5089/-2954 (2135)
function old new delta
__page_vma_mapped_walk - 2928 +2928
try_to_unmap_one 2916 3218 +302
page_mkclean_one 513 802 +289
__replace_page 1439 1719 +280
page_referenced_one 753 1030 +277
page_mapped_in_vma 799 1059 +260
remove_migration_pte 1129 1388 +259
page_idle_clear_pte_refs_one 197 456 +259
write_protect_page 1210 1445 +235
page_idle_clear_pte_refs_one.part 26 - -26
page_vma_mapped_walk 2928 - -2928
Total: Before=37784555, After=37786690, chg +0.01%
I'll drop inlining. It would save ~2k.
--
Kirill A. Shutemov
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