I read from a sample configuration file which says the following:

```
# Sort buffer is used to perform sorts for some ORDER BY and GROUP BY
# queries. If sorted data does not fit into the sort buffer, a disk
# based merge sort is used instead - See the "Sort_merge_passes"
# status variable. Allocated per thread if sort is needed.

```

I have a couple of queries which use filesort. How do I determine what is the size of the buffer I need for queries to run smoothly without hitting the disk?