f2fs: modify the number of issued pages to merge IOs
When testing f2fs on an SSD, I found some 128 page IOs followed by 1 page IO
were issued by f2fs_write_node_pages.
This means that there were some mishandling flows which degrades performance.
Previous f2fs_write_node_pages determines the number of pages to be written,
nr_to_write, as follows.
1. The bio_get_nr_vecs returns 129 pages.
2. The bio_alloc makes a room for 128 pages.
3. The initial 128 pages go into one bio.
4. The existing bio is submitted, and a new bio is prepared for the last 1 page.
5. Finally, sync_node_pages submits the last 1 page bio.
The problem is from the use of bio_get_nr_vecs, so this patch replace it
with max_hw_blocks using queue_max_sectors.
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 392ccb3..d8e84e4 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -734,7 +734,7 @@
do_submit_bio(sbi, type, false);
alloc_new:
if (sbi->bio[type] == NULL) {
- sbi->bio[type] = f2fs_bio_alloc(bdev, bio_get_nr_vecs(bdev));
+ sbi->bio[type] = f2fs_bio_alloc(bdev, max_hw_blocks(sbi));
sbi->bio[type]->bi_sector = SECTOR_FROM_BLOCK(sbi, blk_addr);
/*
* The end_io will be assigned at the sumbission phase.