2013/1/18, Jaegeuk Kim <jaegeuk.kim@xxxxxxxxxxx>:
> 2013-01-18 (금), 16:58 +0900, Namjae Jeon:
>> 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 ?
>
> At this moment, it's very hard to change the segment size due to many
> hardcoded data structures such as SSA, bitmaps, etc.
> Instead, I proposed something like section and zone which are based on
> segment.
> But, somebody will be able to do later. :)
Reviewed-by: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
Okay, I think It is better if you add TODO comment about this to be
fixed by the other.
Talk Incidentally, let me ask you other thing.
get_meta_page never return NULL about allocate page and readpage.
Is there any reason it try to infinitely retry about two case ?
Thanks for reply!
>
>>
>> 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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>> >
>
> --
> Jaegeuk Kim
> Samsung
>
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