Performance degradation on Xeon machine with Workgroup database license

Performance degradation on Xeon machine with Workgroup database license
More CPU's are involved, worse performance goes
Performance is much better with only 1 CPU active
Application uses correct indexes
Using Enterprise database with -spin enabled is not the option
strace shows client spends 50% of its time in semop() function
Machine's CPU's are not utilized at all (CPU usage is zero)
Performance is better with Hyperthreading disabled, but still not same when only 1 CPU is active

Upgrade to 10.1B02 or higher. 

If that is not possible at this time try the following work around:

Temporary fix: Boot the machine using no SMP kernel (when your OS is Linux) or boot with /ONECPU option (when your OS is Windows).

Progress Solution P123085, "Is Progress supported on Intel Core 2 Quad Processors?"