On Fri, Nov 06, 2015 at 02:39:00PM -0800, Andrew Morton wrote: > On Fri, 6 Nov 2015 12:29:21 +0200 "Kirill A. Shutemov" <[email protected]> > wrote: > > > > page_mapcount() is getting pretty bad too. > > > > Do you want me to uninline slow path (PageCompound())? > > I guess so. Uninlining all of page_mapcount() does this: > > gcc-4.4.4: > > text data bss dec hex filename > 973702 273954 831512 2079168 1fb9c0 mm/built-in.o-before > 970148 273954 831000 2075102 1fa9de mm/built-in.o-after > > That's quite a bit of bloat. > > I don't know why bss changed; this usually (always?) happens. Seems > bogus.
Here it is. >From 4bd3af3b6b9498254bd71e8288721dcff641156c Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" <[email protected]> Date: Mon, 9 Nov 2015 01:34:08 +0200 Subject: [PATCH] mm: uninline slowpath of page_mapcount() Let's move page_mapcount() part for compound page into mm/util.c. make allyesconfig: text data bss dec hex filename 188515051 153360535 85458720 427334306 19789aa2 vmlinux.o.before 188512917 153356439 85458720 427328076 1978824c vmlinux.o.after Signed-off-by: Kirill A. Shutemov <[email protected]> --- include/linux/mm.h | 14 +++++--------- mm/util.c | 14 ++++++++++++++ 2 files changed, 19 insertions(+), 9 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index f874d2a1d1a6..72edbbec7b91 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -417,19 +417,15 @@ static inline void page_mapcount_reset(struct page *page) atomic_set(&(page)->_mapcount, -1); } +int __page_mapcount(struct page *page); + static inline int page_mapcount(struct page *page) { - int ret; VM_BUG_ON_PAGE(PageSlab(page), page); - ret = atomic_read(&page->_mapcount) + 1; - if (PageCompound(page)) { - page = compound_head(page); - ret += atomic_read(compound_mapcount_ptr(page)) + 1; - if (PageDoubleMap(page)) - ret--; - } - return ret; + if (unlikely(PageCompound(page))) + return __page_mapcount(page); + return atomic_read(&page->_mapcount) + 1; } #ifdef CONFIG_TRANSPARENT_HUGEPAGE diff --git a/mm/util.c b/mm/util.c index 902b65a43899..68535c0bb9da 100644 --- a/mm/util.c +++ b/mm/util.c @@ -376,6 +376,20 @@ struct address_space *page_mapping(struct page *page) return mapping; } +/* Slow path of page_mapcount() for compound pages */ +int __page_mapcount(struct page *page) +{ + int ret; + + page = compound_head(page); + ret = atomic_read(&page->_mapcount) + 1; + ret += atomic_read(compound_mapcount_ptr(page)) + 1; + if (PageDoubleMap(page)) + ret--; + return ret; +} +EXPORT_SYMBOL_GPL(__page_mapcount); + int overcommit_ratio_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
