Subject: Re: Faster pipes, now with uvm_loan()
To: John Hawkinson <jhawk@MIT.EDU>
From: Anders Magnusson <ragge@ludd.luth.se>
List: tech-kern
Date: 04/29/2001 22:48:42
> | > On a VAX?  Probably that darn "calls" instruction :-)
> | > 
> | It's more likely that it is the time measurement. The smallest measurable
> | time difference on a MicroVAX (of that type) is 10mS. Look at these
> | ping times, for example:
> | 
> | PING olivaw.ludd.luth.se (130.240.16.39): 56 data bytes
> | 64 bytes from 130.240.16.39: icmp_seq=0 ttl=255 time=29.998 ms
> | 64 bytes from 130.240.16.39: icmp_seq=1 ttl=255 time=19.999 ms
> 
> That's pretty ugly/misleading. Is there some way for
> user-level programs to figure out what the time quantum is,
> and perhaps some way for ping to notice and round appropriately?
> 
No, there are no timers at all (at least that I am aware of) on
those MicroVAXen that give better resolution. The older VAXen and
the newer ones have microsecond clocks, but not these.

-- Ragge