Tweak the calculation of minbfree in ffs_dirpref() so that only

those cylinder groups that have at least 75% of the average free
space per cylinder group for that file system are considered as
candidates for the creation of a new directory.  The previous formula
for minbfree would set it to zero if the file system was more than
75% full, which allowed cylinder groups with no free space at all
to be chosen as candidates for directory creation, which resulted
in an expensive search for free blocks for each file that was
subsequently created in that directory.

Modify the calculation of minifree in the same way.

Decrease maxcontigdirs as the file system fills to decrease the
likelyhood that a cluster of directories will overflow the available
space in a cylinder group.

Reviewed by:	mckusick
Tested by:	kmarx@vicor.com
MFC after:	2 weeks

1 files changed, 7 insertions, 7 deletions

diff --git a/sys/ufs/ffs/ffs_alloc.c b/sys/ufs/ffs/ffs_alloc.c
index 288050c..15b81dc 100644
--- a/sys/ufs/ffs/ffs_alloc.c
+++ b/sys/ufs/ffs/ffs_alloc.c
@@ -954,18 +954,18 @@ ffs_dirpref(pip)
 	 * optimal allocation of a directory inode.
 	 */
 	maxndir = min(avgndir + fs->fs_ipg / 16, fs->fs_ipg);
-	minifree = avgifree - fs->fs_ipg / 4;
-	if (minifree < 0)
-		minifree = 0;
-	minbfree = avgbfree - fs->fs_fpg / fs->fs_frag / 4;
-	if (minbfree < 0)
-		minbfree = 0;
+	minifree = avgifree - avgifree / 4;
+	if (minifree < 1)
+		minifree = 1;
+	minbfree = avgbfree - avgbfree / 4;
+	if (minbfree < 1)
+		minbfree = 1;
 	cgsize = fs->fs_fsize * fs->fs_fpg;
 	dirsize = fs->fs_avgfilesize * fs->fs_avgfpdir;
 	curdirsize = avgndir ? (cgsize - avgbfree * fs->fs_bsize) / avgndir : 0;
 	if (dirsize < curdirsize)
 		dirsize = curdirsize;
-	maxcontigdirs = min(cgsize / dirsize, 255);
+	maxcontigdirs = min((avgbfree * fs->fs_bsize) / dirsize, 255);
 	if (fs->fs_avgfpdir > 0)
 		maxcontigdirs = min(maxcontigdirs,
 				    fs->fs_ipg / fs->fs_avgfpdir);