On Fri, 2012-06-15 at 22:00 +0000, Luck, Tony wrote: > > With function tracing the impact to performance is tremendous. Just > > recording two long words is a 130% hit to performance. Now multiply that > > to recording strings. > > If pstore is writing to a flash based backend - then there will be many > milli-seconds of delay. I think the time taken to convert from binary to > ascii would be insignificant. milli-seconds for recording? This would cripple the kernel. On slow machines, incorporating lockdep into function tracing (and other debug options) causes the system to live lock. Tracing the timer interrupt took so long that by the time it finished, the next timer triggered again. Heck, today you can pretty much live lock most machines if you enabled the option 'func_stack_trace' while function tracing without filtering. You may be able to get your system back again, but it usually takes several seconds to acknowledge each key stroke (if you're lucky, but we all know *you* are ;-) If we are talking about milli-seconds to record. Then this is a no go, as it wont be worth adding. I'm thinking their buffering system is much faster than that today, as they have shown examples already. -- Steve _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
