fp assist.  The problem lies with concurrent, potentially frequent
updates of fpu_swa_count, which serves as the throttle for doing the
printk().  A frenzy of concurrent updates will produce a frenzy of
cacheline ping-ponging.

The fix is simple:

Only increment fpu_swa_count when the printk() is about to happen,
which limits the increment to no more than four times every five
seconds.