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GFS2: Add readahead to sequential directory traversal

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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>
This commit is contained in:
Bob Peterson 2011-10-27 12:16:06 -04:00 committed by Steven Whitehouse
parent 20ed0535d3
commit dfe4d34b39
4 changed files with 57 additions and 6 deletions
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56
fs/gfs2/dir.c
View file

@ -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 @@ static int gfs2_dir_read_leaf(struct inode *inode, u64 *offset, void *opaque,
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 @@ static int gfs2_dir_read_leaf(struct inode *inode, u64 *offset, void *opaque,
*/
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);

2
fs/gfs2/dir.h
View file

@ -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);

3
fs/gfs2/export.c
View file

@ -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);

2
fs/gfs2/file.c
View file

@ -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);