with coreutils sort:
```
# or `du -h | sort -hr`
$ cat << EOF | sort -hr
320K  ./x1
412K  ./x2
2.6M  .
952K  ./x3
764K  ./x4
EOF
```

result:
```
2.6M  .
952K  ./x3
764K  ./x4
412K  ./x2
320K  ./x1
```
busybox doesn't support -h yet. would be nice to add it.