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authorDave Chinner <dchinner@redhat.com>2019-08-29 09:04:08 -0700
committerDarrick J. Wong <darrick.wong@oracle.com>2019-08-30 22:43:57 -0700
commit756c6f0f7efe8759ff6dda35d220e2e753e2b0e3 (patch)
treeb7a598123721790184b55e76c9bfb9f32651e634 /fs/xfs
parent610125ab1e4b1b48dcffe74d9d82b0606bf1b923 (diff)
xfs: reverse search directory freespace indexes
When a directory is growing rapidly, new blocks tend to get added at the end of the directory. These end up at the end of the freespace index, and when the directory gets large finding these new freespaces gets expensive. The code does a linear search across the frespace index from the first block in the directory to the last, hence meaning the newly added space is the last index searched. Instead, do a reverse order index search, starting from the last block and index in the freespace index. This makes most lookups for free space on rapidly growing directories O(1) instead of O(N), but should not have any impact on random insert workloads because the average search length is the same regardless of which end of the array we start at. The result is a major improvement in large directory grow rates: create time(sec) / rate (files/s) File count vanilla Prev commit Patched 10k 0.41 / 24.3k 0.42 / 23.8k 0.41 / 24.3k 20k 0.74 / 27.0k 0.76 / 26.3k 0.75 / 26.7k 100k 3.81 / 26.4k 3.47 / 28.8k 3.27 / 30.6k 200k 8.58 / 23.3k 7.19 / 27.8k 6.71 / 29.8k 1M 85.69 / 11.7k 48.53 / 20.6k 37.67 / 26.5k 2M 280.31 / 7.1k 130.14 / 15.3k 79.55 / 25.2k 10M 3913.26 / 2.5k 552.89 / 18.1k Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Diffstat (limited to 'fs/xfs')
-rw-r--r--fs/xfs/libxfs/xfs_dir2_node.c13
1 files changed, 5 insertions, 8 deletions
diff --git a/fs/xfs/libxfs/xfs_dir2_node.c b/fs/xfs/libxfs/xfs_dir2_node.c
index a81f56d9e538..705c4f562758 100644
--- a/fs/xfs/libxfs/xfs_dir2_node.c
+++ b/fs/xfs/libxfs/xfs_dir2_node.c
@@ -1745,10 +1745,11 @@ xfs_dir2_node_find_freeblk(
struct xfs_inode *dp = args->dp;
struct xfs_trans *tp = args->trans;
struct xfs_buf *fbp = NULL;
+ xfs_dir2_db_t firstfbno;
xfs_dir2_db_t lastfbno;
xfs_dir2_db_t ifbno = -1;
xfs_dir2_db_t dbno = -1;
- xfs_dir2_db_t fbno = -1;
+ xfs_dir2_db_t fbno;
xfs_fileoff_t fo;
__be16 *bests = NULL;
int findex = 0;
@@ -1780,7 +1781,6 @@ xfs_dir2_node_find_freeblk(
* We'll start at the beginning of the freespace entries.
*/
ifbno = fblk->blkno;
- fbno = ifbno;
xfs_trans_brelse(tp, fbp);
fbp = NULL;
fblk->bp = NULL;
@@ -1794,12 +1794,9 @@ xfs_dir2_node_find_freeblk(
if (error)
return error;
lastfbno = xfs_dir2_da_to_db(args->geo, (xfs_dablk_t)fo);
+ firstfbno = xfs_dir2_byte_to_db(args->geo, XFS_DIR2_FREE_OFFSET);
- /* If we haven't get a search start block, set it now */
- if (fbno == -1)
- fbno = xfs_dir2_byte_to_db(args->geo, XFS_DIR2_FREE_OFFSET);
-
- for ( ; fbno < lastfbno; fbno++) {
+ for (fbno = lastfbno - 1; fbno >= firstfbno; fbno--) {
/* If it's ifbno we already looked at it. */
if (fbno == ifbno)
continue;
@@ -1822,7 +1819,7 @@ xfs_dir2_node_find_freeblk(
dp->d_ops->free_hdr_from_disk(&freehdr, free);
/* Scan the free entry array for a large enough free space. */
- for (findex = 0; findex < freehdr.nvalid; findex++) {
+ for (findex = freehdr.nvalid - 1; findex >= 0; findex--) {
if (be16_to_cpu(bests[findex]) != NULLDATAOFF &&
be16_to_cpu(bests[findex]) >= length) {
dbno = freehdr.firstdb + findex;