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v0.8.1
https://github.com/torvalds/linux
02 December 2023, 22:23:51 UTC
Revision 1cf24bdbbbd2eb5439796dc399ab1649d150ed1d authored by Jack Steiner on 22 November 2006, 15:55:08 UTC, committed by Tony Luck on 12 December 2006, 19:47:09 UTC 
[IA64] - Reduce overhead of FP exception logging messages
 
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: Jack Steiner <steiner@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
1 parent 8b9c106
History
Tip revision: 1cf24bdbbbd2eb5439796dc399ab1649d150ed1d authored by Jack Steiner on 22 November 2006, 15:55:08 UTC
[IA64] - Reduce overhead of FP exception logging messages
Tip revision: 1cf24bd
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