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Commit a7fdffbd authored by Jaegeuk Kim's avatar Jaegeuk Kim
Browse files

f2fs: avoid issuing small bios due to several dirty node pages 



If some small bios of dirty node pages are supposed to be issued during the
sequential data writes, there-in well-produced consecutive data bios are able
to be split by the small node bios, resulting in performance degradation.
So, let's collect a number of dirty node pages until reaching a threshold.
And, by default, I set the threshold as 2MB, a segment size.

This improves sequential write performance on i5, 512GB SSD (830 w/ SATA2) as
follows.
Before: 231 MB/s -> After: 255 MB/s

Signed-off-by: default avatarJaegeuk Kim <jaegeuk.kim@samsung.com>
Reviewed-by: default avatarNamjae Jeon <namjae.jeon@samsung.com>
parent c01e54b7

fs/f2fs/node.c

+11 −6
Original line number Diff line number Diff line
@@ -1124,6 +1124,12 @@ static int f2fs_write_node_page(struct page *page, 
	return 0;

}



/*

 * It is very important to gather dirty pages and write at once, so that we can

 * submit a big bio without interfering other data writes.

 * Be default, 512 pages (2MB), a segment size, is quite reasonable.

 */

#define COLLECT_DIRTY_NODES	512

static int f2fs_write_node_pages(struct address_space *mapping,

			    struct writeback_control *wbc)

{
@@ -1131,17 +1137,16 @@ static int f2fs_write_node_pages(struct address_space *mapping, 
	struct block_device *bdev = sbi->sb->s_bdev;

	long nr_to_write = wbc->nr_to_write;



	if (wbc->for_kupdate)

		return 0;



	if (get_pages(sbi, F2FS_DIRTY_NODES) == 0)

		return 0;



	/* First check balancing cached NAT entries */

	if (try_to_free_nats(sbi, NAT_ENTRY_PER_BLOCK)) {

		write_checkpoint(sbi, false, false);

		return 0;

	}



	/* collect a number of dirty node pages and write together */

	if (get_pages(sbi, F2FS_DIRTY_NODES) < COLLECT_DIRTY_NODES)

		return 0;



	/* if mounting is failed, skip writing node pages */

	wbc->nr_to_write = bio_get_nr_vecs(bdev);

	sync_node_pages(sbi, 0, wbc);