On Thu, Jan 31, 2013 at 05:39:03PM +0800, Miao Xie wrote:
> This idea is from ext4. By this patch, we can make the dio write parallel,
> and improve the performance.
Interesting, AFAIK, ext4 can only do nolock dio write on some
conditions(should be a overwrite, file size remains unchanged,
no aligned/buffer io in flight), btrfs is ok without any conditions?
thanks,
liubo
>
> 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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