Oops more testing was required....

[jw schultz]

On Wed, Jun 18, 2003 at 09:09:59PM +1000, Martin Pool wrote:
> On 17 Jun 2003, Rogier Wolff <R.E.Wolff at BitWizard.nl> wrote:
> > 
> > Oops. Missed one line in the last patch....
> 
> Thankyou.  That looks good.
> 
> If we're going to make this more accurate it might be worthwhile to
> actually look at how long we really did sleep for, and use that to
> adjust time_to_sleep rather than resetting to zero.

That would have to be a platform specific thing since not
all systems modify the timeout value to reflect the amount
of time not slept.  Nevertheless that is a nice idea.

> Also I'd prefer the variable be called micros_to_sleep or
> us_to_sleep.  Small point I know.

I'm not too keen on forcing the minimum sleep to be 100ms.
That is just too coarse for my taste and tends produce
fits-and-starts stalling on very slow links.

This should be balanced with the "Smoother bandwidth limiting"
thread.  Perhaps setting a minimum sleep to 10ms or
a period based on the value of bwlimit.

> > diff -ur rsync-2.5.6.orig/io.c rsync-2.5.6/io.c
> > +++ rsync-2.5.6/io.c	Tue Jun 17 23:43:49 2003
> > @@ -416,10 +416,19 @@
> >   * use a bit less bandwidth than specified, because it doesn't make up
> >   * for slow periods.  But arguably this is a feature.  In addition, we
> >   * ought to take the time used to write the data into account.
> > + *
> > + * During some phases of big transfers (file XXX is uptodate) this is
> > + * called with a small bytes_written every time. As the kernel has to
> > + * round small waits up to guarantee that we actually wait at least
> > + * the requested number of microseconds, this can become grossly
> > + * inaccurate. We therefore keep a cumulating number of microseconds
> > + * to wait, and only actually perform the sleep when the rouding
> > + * becomes insignificant. (less than 10%) -- REW.
> >   **/
> >  static void sleep_for_bwlimit(int bytes_written)
> >  {
> >  	struct timeval tv;
> > +	static int time_to_sleep = 0; 
> >  
> >  	if (!bwlimit)
> >  		return;
> > @@ -427,9 +436,13 @@
> >  	assert(bytes_written > 0);
> >  	assert(bwlimit > 0);
> >  	
> > -	tv.tv_usec = bytes_written * 1000 / bwlimit;
> > -	tv.tv_sec  = tv.tv_usec / 1000000;
> > -	tv.tv_usec = tv.tv_usec % 1000000;
> > +	time_to_sleep += bytes_written * 1000 / bwlimit; 
> > +
> > +	if (time_to_sleep < 100000) return;
> > +
> > +	tv.tv_sec  = time_to_sleep / 1000000;
> > +	tv.tv_usec = time_to_sleep % 1000000;
> > +	time_to_sleep = 0; 
> >  
> >  	select(0, NULL, NULL, NULL, &tv);
> >  }
> 
> -- 
> Martin 
> -- 
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-- 
________________________________________________________________
	J.W. Schultz            Pegasystems Technologies
	email address:		jw at pegasys.ws

		Remember Cernan and Schmitt