f2fs: avoid issuing small bios due to several dirty node pages (a7fdffbd) · Commits · 戴 / test

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:

Jaegeuk Kim <jaegeuk.kim@samsung.com> Reviewed-by:

Namjae Jeon <namjae.jeon@samsung.com>

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);

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