Re: [PATCH] tsc-disable_B9

[Martin J. Bligh]

>> It's not correlating it to real time that's the problem. It's getting resceduled
>> inbetween calls that hurts. Take your example.
>> 
>> rdtsc
>> mov %eax,%ebx
>> 			<- get rescheduled here
>> rdtsc
>> 
>> Broken. May even take negative "time".
> 
> Statistically irrelevant. When you have 100,000 samples all the
> pre-emption ones drop into the dud sample filter with IRQ disturbance
> and so on.
 
OK, so let's take a better example. People are (I think) mainly using rdtsc
to provide a monotonically increasing counter for database "transaction
order" stamping. I think that's really the case we're worried about. 

M.