• Jack Steiner's avatar
    [IA64] - Reduce overhead of FP exception logging messages · 1cf24bdb
    Jack Steiner authored
    Improve the scalability of the fpswa code that rate-limits
    logging of messages.
    
    There are 2 distinctly different problems in this code.
    
    1) If prctl is used to disable logging, last_time is never
       updated. The result is that fpu_swa_count is zeroed out on
       EVERY fp fault. This causes a very very hot cache line.
       The fix reduces the wallclock time of a 1024p FP exception test
       from 28734 sec to 19 sec!!!
    
    2) On VERY large systems, excessive messages are logged because
       multiple cpus can each reset or increment fpu_swa_count at
       about the same time. The result is that hundreds of messages
       are logged each second. The fixes reduces the logging rate
       to ~1 per second.
    Signed-off-by: default avatarJack Steiner <steiner@sgi.com>
    Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
    1cf24bdb
traps.c 18.1 KB