Re: Intel P6 vs P7 system call performance

[H. Peter Anvin]

Benjamin LaHaise wrote:
> On Tue, Dec 17, 2002 at 11:11:19AM -0800, H. Peter Anvin wrote:
> 
>>>against 0xfffffxxx and "rollback" (or complete) any incomplete
>>>gettimeofday call prior to saving a task's state.  but i bet that test is
>>>undesirable on all interrupt paths.
>>>
>>
>>Exactly.  This is a real problem.
> 
> 
> No, just take the number of context switches before and after the attempt 
> to read the time of day.
> 

How do you do that from userspace, atomically?  A counter in the shared
page?

	-hpa