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Message-Id: <1325764322-10807-3-git-send-email-swhiteho@redhat.com>
Date: Thu, 5 Jan 2012 11:51:48 +0000
From: Steven Whitehouse <swhiteho@...hat.com>
To: linux-kernel@...r.kernel.org, cluster-devel@...hat.com
Cc: Bob Peterson <rpeterso@...hat.com>,
Steven Whitehouse <swhiteho@...hat.com>
Subject: [PATCH 02/16] GFS2: Add readahead to sequential directory traversal
From: Bob Peterson <rpeterso@...hat.com>
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@...hat.com>
Signed-off-by: Steven Whitehouse <swhiteho@...hat.com>
diff --git a/fs/gfs2/dir.c b/fs/gfs2/dir.c
index 8ccad24..9144117 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);
diff --git a/fs/gfs2/dir.h b/fs/gfs2/dir.h
index ff5772f..98c960b 100644
--- a/fs/gfs2/dir.h
+++ b/fs/gfs2/dir.h
@@ -25,7 +25,7 @@ extern int gfs2_dir_add(struct inode *inode, const struct qstr *filename,
const struct gfs2_inode *ip);
extern int gfs2_dir_del(struct gfs2_inode *dip, const struct dentry *dentry);
extern int gfs2_dir_read(struct inode *inode, u64 *offset, void *opaque,
- filldir_t filldir);
+ filldir_t filldir, struct file_ra_state *f_ra);
extern int gfs2_dir_mvino(struct gfs2_inode *dip, const struct qstr *filename,
const struct gfs2_inode *nip, unsigned int new_type);
diff --git a/fs/gfs2/export.c b/fs/gfs2/export.c
index fe9945f..70ba891 100644
--- a/fs/gfs2/export.c
+++ b/fs/gfs2/export.c
@@ -99,6 +99,7 @@ static int gfs2_get_name(struct dentry *parent, char *name,
struct gfs2_holder gh;
u64 offset = 0;
int error;
+ struct file_ra_state f_ra = { .start = 0 };
if (!dir)
return -EINVAL;
@@ -118,7 +119,7 @@ static int gfs2_get_name(struct dentry *parent, char *name,
if (error)
return error;
- error = gfs2_dir_read(dir, &offset, &gnfd, get_name_filldir);
+ error = gfs2_dir_read(dir, &offset, &gnfd, get_name_filldir, &f_ra);
gfs2_glock_dq_uninit(&gh);
diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index ce36a56..46f6f9a 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -105,7 +105,7 @@ static int gfs2_readdir(struct file *file, void *dirent, filldir_t filldir)
return error;
}
- error = gfs2_dir_read(dir, &offset, dirent, filldir);
+ error = gfs2_dir_read(dir, &offset, dirent, filldir, &file->f_ra);
gfs2_glock_dq_uninit(&d_gh);
--
1.7.4
--
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