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 <[email protected]> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
