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: Jaegeuk Kim <[email protected]>
Reviewed-by: Namjae Jeon <[email protected]>
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 @@
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 @@
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);
