diff options
| author | Johannes Thumshirn <jthumshirn@suse.de> | 2019-03-07 17:14:00 +0100 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2019-04-29 19:02:19 +0200 |
| commit | 443c8e2a839f18084cfdb5b0b62d90b8159f48ae (patch) | |
| tree | 96eec479c95b9e5c93cda5d65b6c8d4b21051ca9 /fs/btrfs/file-item.c | |
| parent | a1d198478e92cc8f05c26be746edd1c58f756c0f (diff) | |
btrfs: reduce kmap_atomic time for checksumming
Since commit c40a3d38aff4 ("Btrfs: Compute and look up csums based on
sectorsized blocks") we do a kmap_atomic() on the contents of a bvec.
The code before c40a3d38aff4 had the kmap region just around the
checksumming too.
kmap_atomic() in turn does a preempt_disable() and pagefault_disable(),
so we shouldn't map the data for too long. Reduce the time the bvec's
page is mapped to when we actually need it.
Performance wise it doesn't seem to make a huge difference with a 2 vcpu VM
on a /dev/zram device:
vanilla patched delta
write 17.4MiB/s 17.8MiB/s +0.4MiB/s (+2%)
read 40.6MiB/s 41.5MiB/s +0.9MiB/s (+2%)
The following fio job profile was used in the comparision:
[global]
ioengine=libaio
direct=1
sync=1
norandommap
time_based
runtime=10m
size=100m
group_reporting
numjobs=2
[test]
filename=/mnt/test/fio
rw=randrw
rwmixread=70
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/file-item.c')
| -rw-r--r-- | fs/btrfs/file-item.c | 8 |
1 files changed, 2 insertions, 6 deletions
diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c index cccc75d15970..6fccac9eab96 100644 --- a/fs/btrfs/file-item.c +++ b/fs/btrfs/file-item.c @@ -458,8 +458,6 @@ blk_status_t btrfs_csum_one_bio(struct inode *inode, struct bio *bio, BUG_ON(!ordered); /* Logic error */ } - data = kmap_atomic(bvec.bv_page); - nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info, bvec.bv_len + fs_info->sectorsize - 1); @@ -469,7 +467,6 @@ blk_status_t btrfs_csum_one_bio(struct inode *inode, struct bio *bio, offset < ordered->file_offset) { unsigned long bytes_left; - kunmap_atomic(data); sums->len = this_sum_bytes; this_sum_bytes = 0; btrfs_add_ordered_sum(inode, ordered, sums); @@ -489,16 +486,16 @@ blk_status_t btrfs_csum_one_bio(struct inode *inode, struct bio *bio, sums->bytenr = ((u64)bio->bi_iter.bi_sector << 9) + total_bytes; index = 0; - - data = kmap_atomic(bvec.bv_page); } sums->sums[index] = ~(u32)0; + data = kmap_atomic(bvec.bv_page); sums->sums[index] = btrfs_csum_data(data + bvec.bv_offset + (i * fs_info->sectorsize), sums->sums[index], fs_info->sectorsize); + kunmap_atomic(data); btrfs_csum_final(sums->sums[index], (char *)(sums->sums + index)); index++; @@ -507,7 +504,6 @@ blk_status_t btrfs_csum_one_bio(struct inode *inode, struct bio *bio, total_bytes += fs_info->sectorsize; } - kunmap_atomic(data); } this_sum_bytes = 0; btrfs_add_ordered_sum(inode, ordered, sums); |