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authorBob Peterson <rpeterso@redhat.com>2011-10-27 12:16:06 -0400
committerSteven Whitehouse <swhiteho@redhat.com>2011-11-08 09:52:12 +0000
commitdfe4d34b39b80faff52489f950a18523da7581bf (patch)
treebe478e2c4988612eef88a1669f774dd8f9f9b8af /fs/gfs2/dir.c
parent20ed0535d35b74c9e4fa5777766d6e836fe3c90c (diff)
GFS2: Add readahead to sequential directory traversal
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. Signed-off-by: Bob Peterson <rpeterso@redhat.com> Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Diffstat (limited to 'fs/gfs2/dir.c')
-rw-r--r--fs/gfs2/dir.c56
1 files changed, 53 insertions, 3 deletions
diff --git a/fs/gfs2/dir.c b/fs/gfs2/dir.c
index 8ccad2467cb6..91441171bf25 100644
--- a/fs/gfs2/dir.c
+++ b/fs/gfs2/dir.c
@@ -76,6 +76,8 @@
#define IS_LEAF 1 /* Hashed (leaf) directory */
#define IS_DINODE 2 /* Linear (stuffed dinode block) directory */
+#define MAX_RA_BLOCKS 32 /* max read-ahead blocks */
+
#define gfs2_disk_hash2offset(h) (((u64)(h)) >> 1)
#define gfs2_dir_offset2hash(p) ((u32)(((u64)(p)) << 1))
@@ -1376,6 +1378,50 @@ out:
return error;
}
+/* gfs2_dir_readahead - Issue read-ahead requests for leaf blocks.
+ *
+ * Note: we can't calculate each index like dir_e_read can because we don't
+ * have the leaf, and therefore we don't have the depth, and therefore we
+ * don't have the length. So we have to just read enough ahead to make up
+ * for the loss of information. */
+static void gfs2_dir_readahead(struct inode *inode, unsigned hsize, u32 index,
+ struct file_ra_state *f_ra)
+{
+ struct gfs2_inode *ip = GFS2_I(inode);
+ struct gfs2_glock *gl = ip->i_gl;
+ struct buffer_head *bh;
+ u64 blocknr = 0, last;
+ unsigned count;
+
+ /* First check if we've already read-ahead for the whole range. */
+ if (!f_ra || index + MAX_RA_BLOCKS < f_ra->start)
+ return;
+
+ f_ra->start = max((pgoff_t)index, f_ra->start);
+ for (count = 0; count < MAX_RA_BLOCKS; count++) {
+ if (f_ra->start >= hsize) /* if exceeded the hash table */
+ break;
+
+ last = blocknr;
+ blocknr = be64_to_cpu(ip->i_hash_cache[f_ra->start]);
+ f_ra->start++;
+ if (blocknr == last)
+ continue;
+
+ 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
@@ -1388,7 +1434,7 @@ out:
*/
static int dir_e_read(struct inode *inode, u64 *offset, void *opaque,
- filldir_t filldir)
+ filldir_t filldir, struct file_ra_state *f_ra)
{
struct gfs2_inode *dip = GFS2_I(inode);
u32 hsize, len = 0;
@@ -1402,10 +1448,14 @@ static int dir_e_read(struct inode *inode, u64 *offset, void *opaque,
hash = gfs2_dir_offset2hash(*offset);
index = hash >> (32 - dip->i_depth);
+ if (f_ra && dip->i_hash_cache == NULL)
+ f_ra->start = 0;
lp = gfs2_dir_get_hash_table(dip);
if (IS_ERR(lp))
return PTR_ERR(lp);
+ gfs2_dir_readahead(inode, hsize, index, f_ra);
+
while (index < hsize) {
error = gfs2_dir_read_leaf(inode, offset, opaque, filldir,
&copied, &depth,
@@ -1423,7 +1473,7 @@ static int dir_e_read(struct inode *inode, u64 *offset, void *opaque,
}
int gfs2_dir_read(struct inode *inode, u64 *offset, void *opaque,
- filldir_t filldir)
+ filldir_t filldir, struct file_ra_state *f_ra)
{
struct gfs2_inode *dip = GFS2_I(inode);
struct gfs2_sbd *sdp = GFS2_SB(inode);
@@ -1437,7 +1487,7 @@ int gfs2_dir_read(struct inode *inode, u64 *offset, void *opaque,
return 0;
if (dip->i_diskflags & GFS2_DIF_EXHASH)
- return dir_e_read(inode, offset, opaque, filldir);
+ return dir_e_read(inode, offset, opaque, filldir, f_ra);
if (!gfs2_is_stuffed(dip)) {
gfs2_consist_inode(dip);