Hello Ingo and all, In function arch/x86/kernel/smpboot.c::smp_callin(), we do a calibrate_delay(), the reason behind doing this is commented as follows:
* Get our bogomips. * Update loops_per_jiffy in cpu_data. Previous call to * smp_store_cpu_info() stored a value that is close but not as * accurate as the value just calculated. Now, if we look at the init/calibrate.c::calibrate_delay() - a percpu variable cpu_loops_per_jiffy is used to cache up the loops_per_jiffy value. If cpu_loop_per_jiffy value is set (which should be after first run) then it prevents calculating new loops_per_jiffy thus the accuracy expected from the callsite isn't getable (I'm thinking about cpu hotpluging for few times). Is it not something that we should care about? Is lpj value is that important to recalculate (when mostly we read from tsc)? And, if it's important, how cpu_loop_per_jiffy is helping? Thanks, Rakib. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/