For those interested, there's a brand new Con Kolivas -ck1 patch against kernel 2.4.21-rc7. I just tried it on Mandrake 9.1, and so far so good, except no supermount (if one cares).
I just applied the 2.4.21-rc7 patch to 2.4.20 source (did mrproper first), then applied the ck1 patch, and then did make xconfig. I loaded the stock Mandrake 9.1 2.4.21-pre .config file, then I selected for my cpu (athlon), said no to some various hardware devices and options I never use or have. (wound up with a 1.1MB kernel image)
Then did the usual:
su to root, and:
Then I checked /boot and /etc/lilo.conf just to make sure all was correct.
In my case, I removed the old 2.4.20-ck7 kernel and 2.4.20-ck7 /lib/modules, and lilo entries. Ran lilo again to finish up, and rebooted,
Booted fine, and I'm now using the new patched preemptive kernel from Con Kolivas. Seems really responsive.