http://www.freebsd.org/doc/en/books/developers-handbook/kerneldebug-deadlocks.html My experience with ia64 -current shows that kernel option DIAGNOSTIC adds too much overhead to the system. It seems the extra debugging consumes 100% of system resources and the system can do nothing else. In particular, the symptoms are: - kernel thread taskq, which consumes 100% CPU, e.g.: PID USERNAME PRI NICE SIZE RES STATE C TIME CPU COMMAND 0 root 8 0 0K 416K CPU0 0 186:02 100.00% kernel{thread taskq} - system extremely unresponsive, requiring over 1 min(!) to execute ls, df, ps, date, uptime, etc. - lots of messages similar to: Expensive timeout(9) function: 0x9ffc000000dca8b0(0) 0.036993424 s Fix: Removing DIAGNOSTIC gets the system back to usable. I suggest adding a warning to the above page, something like: "Be warned that option DIAGNOSTIC adds a lot of extra overheads to the system, which can result in very noticeable degradation of performance." And then listing the above sysmptoms as examples of degraded performance. Or something like this. I've discussed this with marcel@ and he agrees with me.
Responsible Changed From-To: freebsd-bugs->freebsd-doc reclassify.
For bugs matching the following criteria: Status: In Progress Changed: (is less than) 2014-06-01 Reset to default assignee and clear in-progress tags. Mail being skipped