Hi,
Were we not intending to make this turn itself off in cases where it
produces no benefit? I thought the plan was to track the state via the
file descriptor in order to avoid readingahead the same blocks over and
over again too,
Steve.
On Tue, 2011-10-04 at 12:39 -0400, Bob Peterson wrote:
> Hi,
>
> This patch adds read-ahead capability to GFS2's
> directory hash table management. It greatly improves
> performance for some directory operations. For example:
> In one of my file systems that has 1000 directories, each
> of which has 1000 files, time to execute a recursive
> ls (time ls -fR /mnt/gfs2 > /dev/null) was reduced
> from 2m2.814s on a stock kernel to 0m45.938s.
>
> Regards,
>
> Bob Peterson
> Red Hat File Systems
>
> Signed-off-by: Bob Peterson <rpete...@redhat.com>
> --
> fs/gfs2/dir.c | 33 +++++++++++++++++++++++++++++++++
> 1 files changed, 33 insertions(+), 0 deletions(-)
>
> diff --git a/fs/gfs2/dir.c b/fs/gfs2/dir.c
> index 2045d70..9b4262e 100644
> --- a/fs/gfs2/dir.c
> +++ b/fs/gfs2/dir.c
> @@ -1376,6 +1376,37 @@ out:
> return error;
> }
>
> +static void gfs2_dir_readahead(struct inode *inode, __be64 *ht, unsigned
> hsize,
> + u32 index)
> +{
> + struct gfs2_inode *ip = GFS2_I(inode);
> + struct gfs2_glock *gl = ip->i_gl;
> + struct buffer_head *bh;
> + u64 blocknr = 0, last;
> + unsigned count = 0;
> +
> + while (index < hsize) {
> + last = blocknr;
> + blocknr = be64_to_cpu(ht[index++]);
> + if (blocknr == last)
> + continue;
> + count++;
> + if (count > 128)
> + break;
> + bh = gfs2_getbuf(gl, blocknr, 1);
> + if (trylock_buffer(bh)) {
> + if (buffer_uptodate(bh)) {
> + unlock_buffer(bh);
> + brelse(bh);
> + continue;
> + }
> + bh->b_end_io = end_buffer_read_sync;
> + submit_bh(READA | REQ_META, bh);
> + continue;
> + }
> + brelse(bh);
> + }
> +}
>
> /**
> * dir_e_read - Reads the entries from a directory into a filldir buffer
> @@ -1406,6 +1437,8 @@ static int dir_e_read(struct inode *inode, u64 *offset,
> void *opaque,
> if (IS_ERR(lp))
> return PTR_ERR(lp);
>
> + gfs2_dir_readahead(inode, lp, hsize, index);
> +
> while (index < hsize) {
> error = gfs2_dir_read_leaf(inode, offset, opaque, filldir,
> &copied, &depth,
>
