(at least smp) fc5 kernels after 1788 have excessive kernel overhead

[Anne & Lynn Wheeler]

dell poweredge 2400 dual 1ghz processors. (at least smp) kernels after
1788 have enormous kernel processor overhead.

applications that are i/o bound on kernel 1788 or earlier ... are
severely degraded on kernels after 1788 with 100% processor utilization
... almost all of it in kernel. when applications are idle ... the
processor use goes idle (aka it isn't some sort of background looping
process ... but seems to be some sort extra kernel overhead).

this is machine that i had problems with scsi i/o hanging after fc4 smp
kernel 1278  (non-smp kernel didn't have scsi i/o hang problem). smp
kernel hanging problem cleared up with fresh fc5 install.