From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Jan Kara To: Cc: Mel Gorman , "Kirill A. Shutemov" , , Jan Kara Subject: [PATCH 1/7] mm: Speedup cancel_dirty_page() for clean pages Date: Tue, 10 Oct 2017 17:19:31 +0200 Message-Id: <20171010151937.26984-2-jack@suse.cz> In-Reply-To: <20171010151937.26984-1-jack@suse.cz> References: <20171010151937.26984-1-jack@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: cancel_dirty_page() does quite some work even for clean pages (fetching of mapping, locking of memcg, atomic bit op on page flags) so it accounts for ~2.5% of cost of truncation of a clean page. That is not much but still dumb for something we don't need at all. Check whether a page is actually dirty and avoid any work if not. Acked-by: Mel Gorman Signed-off-by: Jan Kara --- include/linux/mm.h | 8 +++++++- mm/page-writeback.c | 4 ++-- 2 files changed, 9 insertions(+), 3 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 065d99deb847..d14a9bb2a3d7 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1430,7 +1430,13 @@ void account_page_cleaned(struct page *page, struct address_space *mapping, struct bdi_writeback *wb); int set_page_dirty(struct page *page); int set_page_dirty_lock(struct page *page); -void cancel_dirty_page(struct page *page); +void __cancel_dirty_page(struct page *page); +static inline void cancel_dirty_page(struct page *page) +{ + /* Avoid atomic ops, locking, etc. when not actually needed. */ + if (PageDirty(page)) + __cancel_dirty_page(page); +} int clear_page_dirty_for_io(struct page *page); int get_cmdline(struct task_struct *task, char *buffer, int buflen); diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 0b9c5cbe8eba..c3bed3f5cd24 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -2623,7 +2623,7 @@ EXPORT_SYMBOL(set_page_dirty_lock); * page without actually doing it through the VM. Can you say "ext3 is * horribly ugly"? Thought you could. */ -void cancel_dirty_page(struct page *page) +void __cancel_dirty_page(struct page *page) { struct address_space *mapping = page_mapping(page); @@ -2644,7 +2644,7 @@ void cancel_dirty_page(struct page *page) ClearPageDirty(page); } } -EXPORT_SYMBOL(cancel_dirty_page); +EXPORT_SYMBOL(__cancel_dirty_page); /* * Clear a page's dirty flag, while caring for dirty memory accounting. -- 2.12.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org