This idea is from ext4. By this patch, we can make the dio write parallel,
and improve the performance.
We needn't worry about the race between dio write and truncate, because the
truncate need wait untill all the dio write end.
And we also needn't worry about the race between dio write and punch hole,
because we have extent lock to protect our operation.
I ran fio to test the performance of this feature.
== Hardware ==
CPU: Intel(R) Core(TM)2 Duo CPU E7500 @ 2.93GHz
Mem: 2GB
SSD: Intel X25-M 120GB (Test Partition: 60GB)
== config file ==
[global]
ioengine=psync
direct=1
bs=4k
size=32G
runtime=60
directory=/mnt/btrfs/
filename=testfile
group_reporting
thread
[file1]
numjobs=1 # 2 4
rw=randwrite
== result (KBps) ==
write 1 2 4
lock 24936 24738 24726
nolock 24962 30866 32101
== result (iops) ==
write 1 2 4
lock 6234 6184 6181
nolock 6240 7716 8025
Signed-off-by: Miao Xie <miaox@xxxxxxxxxxxxxx>
---
fs/btrfs/inode.c | 24 +++++++++++++-----------
1 file changed, 13 insertions(+), 11 deletions(-)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index d17a04b..091593a 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6589,31 +6589,33 @@ static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
int flags = 0;
- bool wakeup = false;
+ bool wakeup = true;
int ret;
if (check_direct_IO(BTRFS_I(inode)->root, rw, iocb, iov,
offset, nr_segs))
return 0;
- if (rw == READ) {
- atomic_inc(&inode->i_dio_count);
- smp_mb__after_atomic_inc();
- if (unlikely(test_bit(BTRFS_INODE_READDIO_NEED_LOCK,
- &BTRFS_I(inode)->runtime_flags))) {
- inode_dio_done(inode);
- flags = DIO_LOCKING | DIO_SKIP_HOLES;
- } else {
- wakeup = true;
- }
+ atomic_inc(&inode->i_dio_count);
+ smp_mb__after_atomic_inc();
+ if (rw == WRITE) {
+ mutex_unlock(&inode->i_mutex);
+ } else if (unlikely(test_bit(BTRFS_INODE_READDIO_NEED_LOCK,
+ &BTRFS_I(inode)->runtime_flags))) {
+ inode_dio_done(inode);
+ flags = DIO_LOCKING | DIO_SKIP_HOLES;
+ wakeup = false;
}
ret = __blockdev_direct_IO(rw, iocb, inode,
BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev,
iov, offset, nr_segs, btrfs_get_blocks_direct, NULL,
btrfs_submit_direct, flags);
+
if (wakeup)
inode_dio_done(inode);
+ if (rw == WRITE)
+ mutex_lock(&inode->i_mutex);
return ret;
}
--
1.7.11.7
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