| Message ID | 20240820122210.660140-1-david@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v1] mm: always inline _compound_head() with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP=y | expand |
On 8/20/24 08:22, David Hildenbrand wrote: > We already force-inline page_fixed_fake_head(), page_is_fake_head() > and PageTail(), however the compiler might decide that _compound_head() > is not worthy to be inlined, because of page_fixed_fake_head(). > > The result is that, for example, PageAnonExclusive() now might involve > a function call when checking PageHuge(), which performs a > page_folio()->_compound_head() call. This can lead to a slight regression > of the stress-ng.clone benchmark. > > This is not super-urgent to fix, but always inlining _compound_head() > seems like the obvious thing to do for this primitive, similar to the > other ones. > > This change restores the slight regression and a compilation with > CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP=y shows no relevant bloat [2]: > > add/remove: 15/14 grow/shrink: 79/87 up/down: 12836/-13917 (-1081) > ... > Total: Before=32786363, After=32785282, chg -0.00% > > [1] https://lkml.kernel.org/r/817150f2-abf7-430f-9973-540bd6cdd26f@intel.com > [2] https://lore.kernel.org/all/116e117c-2821-401d-8e62-b85cdec37f4a@redhat.com/ > > Fixes: c0bff412e67b ("mm: allow anon exclusive check over hugetlb tail pages") > Reported-by: kernel test robot <oliver.sang@intel.com> > Closes: https://lore.kernel.org/oe-lkp/202407301049.5051dc19-oliver.sang@intel.com > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Peter Xu <peterx@redhat.com> > Signed-off-by: David Hildenbrand <david@redhat.com> > --- > include/linux/page-flags.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index b753d158762fc..af58b2ad854c3 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -233,7 +233,7 @@ static __always_inline int page_is_fake_head(const struct page *page) > return page_fixed_fake_head(page) != page; > } > > -static inline unsigned long _compound_head(const struct page *page) > +static __always_inline unsigned long _compound_head(const struct page *page) > { > unsigned long head = READ_ONCE(page->compound_head); > Tested-by: Yin Fengwei <fengwei.yin@intel.com> Regards Yin, Fengwei
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index b753d158762fc..af58b2ad854c3 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -233,7 +233,7 @@ static __always_inline int page_is_fake_head(const struct page *page) return page_fixed_fake_head(page) != page; } -static inline unsigned long _compound_head(const struct page *page) +static __always_inline unsigned long _compound_head(const struct page *page) { unsigned long head = READ_ONCE(page->compound_head);
We already force-inline page_fixed_fake_head(), page_is_fake_head() and PageTail(), however the compiler might decide that _compound_head() is not worthy to be inlined, because of page_fixed_fake_head(). The result is that, for example, PageAnonExclusive() now might involve a function call when checking PageHuge(), which performs a page_folio()->_compound_head() call. This can lead to a slight regression of the stress-ng.clone benchmark. This is not super-urgent to fix, but always inlining _compound_head() seems like the obvious thing to do for this primitive, similar to the other ones. This change restores the slight regression and a compilation with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP=y shows no relevant bloat [2]: add/remove: 15/14 grow/shrink: 79/87 up/down: 12836/-13917 (-1081) ... Total: Before=32786363, After=32785282, chg -0.00% [1] https://lkml.kernel.org/r/817150f2-abf7-430f-9973-540bd6cdd26f@intel.com [2] https://lore.kernel.org/all/116e117c-2821-401d-8e62-b85cdec37f4a@redhat.com/ Fixes: c0bff412e67b ("mm: allow anon exclusive check over hugetlb tail pages") Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202407301049.5051dc19-oliver.sang@intel.com Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Xu <peterx@redhat.com> Signed-off-by: David Hildenbrand <david@redhat.com> --- include/linux/page-flags.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)