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f2fs: modify the number of issued pages to merge IOs

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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>
This commit is contained in:
Jaegeuk Kim 2013-04-29 16:58:39 +09:00
parent b743ba78ae
commit ac5d156c78
3 changed files with 14 additions and 5 deletions
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6
fs/f2fs/node.c
View File

@ -1171,7 +1171,6 @@ static int f2fs_write_node_pages(struct address_space *mapping,
struct writeback_control *wbc)
{
struct f2fs_sb_info *sbi = F2FS_SB(mapping->host->i_sb);
struct block_device *bdev = sbi->sb->s_bdev;
long nr_to_write = wbc->nr_to_write;
/* First check balancing cached NAT entries */
@ -1185,10 +1184,9 @@ static int f2fs_write_node_pages(struct address_space *mapping,
return 0;
/* if mounting is failed, skip writing node pages */
wbc->nr_to_write = bio_get_nr_vecs(bdev);
wbc->nr_to_write = max_hw_blocks(sbi);
sync_node_pages(sbi, 0, wbc);
wbc->nr_to_write = nr_to_write -
(bio_get_nr_vecs(bdev) - wbc->nr_to_write);
wbc->nr_to_write = nr_to_write - (max_hw_blocks(sbi) - wbc->nr_to_write);
return 0;
}

2
fs/f2fs/segment.c
View File

@ -734,7 +734,7 @@ static void submit_write_page(struct f2fs_sb_info *sbi, struct page *page,
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.

11
fs/f2fs/segment.h
View File

@ -8,6 +8,8 @@
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/blkdev.h>
/* constant macro */
#define NULL_SEGNO ((unsigned int)(~0))
#define NULL_SECNO ((unsigned int)(~0))
@ -86,6 +88,8 @@
#define SECTOR_FROM_BLOCK(sbi, blk_addr) \
(blk_addr << ((sbi)->log_blocksize - F2FS_LOG_SECTOR_SIZE))
#define SECTOR_TO_BLOCK(sbi, sectors) \
(sectors >> ((sbi)->log_blocksize - F2FS_LOG_SECTOR_SIZE))
/* during checkpoint, bio_private is used to synchronize the last bio */
struct bio_private {
@ -624,3 +628,10 @@ static inline bool sec_usage_check(struct f2fs_sb_info *sbi, unsigned int secno)
return true;
return false;
}
static inline unsigned int max_hw_blocks(struct f2fs_sb_info *sbi)
{
struct block_device *bdev = sbi->sb->s_bdev;
struct request_queue *q = bdev_get_queue(bdev);
return SECTOR_TO_BLOCK(sbi, queue_max_sectors(q));
}