2013/1/18, Jaegeuk Kim <jaegeuk.kim@xxxxxxxxxxx>:
> 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@xxxxxxxxxxx>
> ---
> fs/f2fs/node.c | 17 +++++++++++------
> 1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index f177c01..9bda63c 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -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
Hi Jaeguek.
It is just my opinion.
One of f2fs advantages is that user can set segment size to fit own device.
For future, Is it not good to use segment size set by user(from
superblock) instead of fixed size ?
Thanks.
> 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);
> --
> 1.8.0.1.250.gb7973fb
>
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