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From: Jan Kara <jack@suse.cz>
To: <linux-mm@kvack.org>
Cc: Mel Gorman <mgorman@suse.de>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	<linux-fsdevel@vger.kernel.org>, Jan Kara <jack@suse.cz>
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> (raw)
In-Reply-To: <20171010151937.26984-1-jack@suse.cz>

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 <mgorman@suse.de>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 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

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  reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-10 15:19 [PATCH 0/7 v1] Speed up page cache truncation Jan Kara
2017-10-10 15:19 ` Jan Kara [this message]
2017-10-10 15:19 ` [PATCH 2/7] mm: Refactor truncate_complete_page() Jan Kara
2017-10-10 15:19 ` [PATCH 3/7] mm: Factor out page cache page freeing into a separate function Jan Kara
2017-10-10 15:19 ` [PATCH 4/7] mm: Move accounting updates before page_cache_tree_delete() Jan Kara
2017-10-10 15:19 ` [PATCH 5/7] mm: Move clearing of page->mapping to page_cache_tree_delete() Jan Kara
2017-10-10 15:19 ` [PATCH 6/7] mm: Factor out checks and accounting from __delete_from_page_cache() Jan Kara
2017-10-10 15:19 ` [PATCH 7/7] mm: Batch radix tree operations when truncating pages Jan Kara
2017-10-11  7:39   ` Mel Gorman
2017-10-17 23:05   ` Andrew Morton
2017-10-18 10:44     ` Jan Kara
2017-10-10 17:25 ` [PATCH 0/7 v1] Speed up page cache truncation Andi Kleen
2017-10-11  8:06   ` Jan Kara
2017-10-11 16:51     ` Andi Kleen
2017-10-11 17:34     ` Dave Hansen
2017-10-11 17:59       ` Mel Gorman
2017-10-11 18:37         ` Andi Kleen
2017-10-11 21:06       ` Jan Kara
2017-10-11 21:24         ` Dave Chinner
2017-10-12  9:09           ` Mel Gorman
2017-10-12 14:07           ` Jan Kara
2017-10-17 16:21 [PATCH 0/7 v2] " Jan Kara
2017-10-17 16:21 ` [PATCH 1/7] mm: Speedup cancel_dirty_page() for clean pages Jan Kara

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