Re: nanosleep resolution, jiffies vs microseconds

["Paul E. McKenney" <paulmck@us.ibm.com>]

On Wed, Dec 08, 2004 at 09:05:04AM -0800, Mike Kravetz wrote:
> On Wed, Dec 08, 2004 at 08:47:48AM -0800, Darren Hart wrote:
> > I am looking at trying to improve the latency of nanosleep for short
> > sleep times (~1ms).  After reading Martin Schwidefsky's post for cputime
> > on s390 (Message-ID:
> > <20041111171439.GA4900@mschwid3.boeblingen.de.ibm.com>), it seems to me
> > that we may be able to accomplish this by storing the expire time in
> > microseconds rather than jiffies.
> 
> My only question would be 'why'?  Is there some environment where this
> is an issue? -OR- Is this just 'something to do'?  Seems to me that the
> only environment where this could be an issue is for 'realtime' tasks.
> For non-realtime, I would guess that the variability of preemption/scheduling 
> makes this almost a non-issue.  In environments where I have seen heavy
> use of nanosleep, there were other scheduling issues that almost always
> cause one to 'sleep' longer than the specified time.  I'm not opposed to
> work in this area.  Just curious as to why?

This is indeed for realtime work.

						Thanx, Paul