cvs is slooooooow with large directories

[Andrew Morton]

Howdy.

This is probably a frequently-whined-question, but what the hey.

I'm sitting here doing a `cvs co -ko' of my kernel tree.  It happens to
have three directories in it, each of which contains about 16,000 small
files.

On a dual 2.7GHz power4, the cvs client has racked up an hour of CPU time
so far.  There's something in there which is quadratic (or worse) in the
number of files in a directory.  It's doing less than two files per
second in those big directories.

CVS 1.11.5 is fine - it doesn't have this problem at all.  It'll do this
tree in 2.5 minutes.

CVS 1.11.17 is slow - it takes well over an hour.

What happened?