diff options
author | Dave Chinner <dchinner@redhat.com> | 2019-08-29 09:04:07 -0700 |
---|---|---|
committer | Darrick J. Wong <darrick.wong@oracle.com> | 2019-08-30 22:43:57 -0700 |
commit | 610125ab1e4b1b48dcffe74d9d82b0606bf1b923 (patch) | |
tree | 37122bf616dc4405830e16529859e4a4961b758c /fs/xfs | |
parent | 0e822255f95db400e56e19773e04755d79b50bda (diff) | |
download | linux-610125ab1e4b1b48dcffe74d9d82b0606bf1b923.tar.bz2 |
xfs: speed up directory bestfree block scanning
When running a "create millions inodes in a directory" test
recently, I noticed we were spending a huge amount of time
converting freespace block headers from disk format to in-memory
format:
31.47% [kernel] [k] xfs_dir2_node_addname
17.86% [kernel] [k] xfs_dir3_free_hdr_from_disk
3.55% [kernel] [k] xfs_dir3_free_bests_p
We shouldn't be hitting the best free block scanning code so hard
when doing sequential directory creates, and it turns out there's
a highly suboptimal loop searching the the best free array in
the freespace block - it decodes the block header before checking
each entry inside a loop, instead of decoding the header once before
running the entry search loop.
This makes a massive difference to create rates. Profile now looks
like this:
13.15% [kernel] [k] xfs_dir2_node_addname
3.52% [kernel] [k] xfs_dir3_leaf_check_int
3.11% [kernel] [k] xfs_log_commit_cil
And the wall time/average file create rate differences are
just as stark:
create time(sec) / rate (files/s)
File count vanilla patched
10k 0.41 / 24.3k 0.42 / 23.8k
20k 0.74 / 27.0k 0.76 / 26.3k
100k 3.81 / 26.4k 3.47 / 28.8k
200k 8.58 / 23.3k 7.19 / 27.8k
1M 85.69 / 11.7k 48.53 / 20.6k
2M 280.31 / 7.1k 130.14 / 15.3k
The larger the directory, the bigger the performance improvement.
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.c | 97 |
1 files changed, 34 insertions, 63 deletions
diff --git a/fs/xfs/libxfs/xfs_dir2_node.c b/fs/xfs/libxfs/xfs_dir2_node.c index 93254f45a5f9..a81f56d9e538 100644 --- a/fs/xfs/libxfs/xfs_dir2_node.c +++ b/fs/xfs/libxfs/xfs_dir2_node.c @@ -1750,8 +1750,8 @@ xfs_dir2_node_find_freeblk( xfs_dir2_db_t dbno = -1; xfs_dir2_db_t fbno = -1; xfs_fileoff_t fo; - __be16 *bests; - int findex; + __be16 *bests = NULL; + int findex = 0; int error; /* @@ -1781,14 +1781,14 @@ xfs_dir2_node_find_freeblk( */ ifbno = fblk->blkno; fbno = ifbno; + xfs_trans_brelse(tp, fbp); + fbp = NULL; + fblk->bp = NULL; } - ASSERT(dbno == -1); - findex = 0; /* * If we don't have a data block yet, we're going to scan the freespace - * blocks looking for one. Figure out what the highest freespace block - * number is. + * data for a data block with enough free space in it. */ error = xfs_bmap_last_offset(dp, &fo, XFS_DATA_FORK); if (error) @@ -1799,70 +1799,41 @@ xfs_dir2_node_find_freeblk( if (fbno == -1) fbno = xfs_dir2_byte_to_db(args->geo, XFS_DIR2_FREE_OFFSET); - /* - * While we haven't identified a data block, search the freeblock - * data for a good data block. If we find a null freeblock entry, - * indicating a hole in the data blocks, remember that. - */ - while (dbno == -1) { - /* - * If we don't have a freeblock in hand, get the next one. - */ - if (fbp == NULL) { - /* - * If it's ifbno we already looked at it. - */ - if (++fbno == ifbno) - fbno++; - /* - * If it's off the end we're done. - */ - if (fbno >= lastfbno) - break; - /* - * Read the block. There can be holes in the - * freespace blocks, so this might not succeed. - * This should be really rare, so there's no reason - * to avoid it. - */ - error = xfs_dir2_free_try_read(tp, dp, - xfs_dir2_db_to_da(args->geo, fbno), - &fbp); - if (error) - return error; - if (!fbp) - continue; - free = fbp->b_addr; - findex = 0; - } + for ( ; fbno < lastfbno; fbno++) { + /* If it's ifbno we already looked at it. */ + if (fbno == ifbno) + continue; + /* - * Look at the current free entry. Is it good enough? - * - * The bests initialisation should be where the bufer is read in - * the above branch. But gcc is too stupid to realise that bests - * and the freehdr are actually initialised if they are placed - * there, so we have to do it here to avoid warnings. Blech. + * Read the block. There can be holes in the freespace blocks, + * so this might not succeed. This should be really rare, so + * there's no reason to avoid it. */ + error = xfs_dir2_free_try_read(tp, dp, + xfs_dir2_db_to_da(args->geo, fbno), + &fbp); + if (error) + return error; + if (!fbp) + continue; + + free = fbp->b_addr; bests = dp->d_ops->free_bests_p(free); dp->d_ops->free_hdr_from_disk(&freehdr, free); - if (be16_to_cpu(bests[findex]) != NULLDATAOFF && - be16_to_cpu(bests[findex]) >= length) - dbno = freehdr.firstdb + findex; - else { - /* - * Are we done with the freeblock? - */ - if (++findex == freehdr.nvalid) { - /* - * Drop the block. - */ - xfs_trans_brelse(tp, fbp); - fbp = NULL; - if (fblk && fblk->bp) - fblk->bp = NULL; + + /* Scan the free entry array for a large enough free space. */ + for (findex = 0; findex < freehdr.nvalid; findex++) { + if (be16_to_cpu(bests[findex]) != NULLDATAOFF && + be16_to_cpu(bests[findex]) >= length) { + dbno = freehdr.firstdb + findex; + goto found_block; } } + + /* Didn't find free space, go on to next free block */ + xfs_trans_brelse(tp, fbp); } + found_block: *dbnop = dbno; *fbpp = fbp; |