Feature Request - Load Throttling

jw schultz jw at pegasys.ws
Wed Feb 18 02:59:04 GMT 2004

On Tue, Feb 17, 2004 at 06:47:19PM -0800, Marc Perkel wrote:
> Actually - the problem is disk IO. And the disk IO is what makes the 
> load levels go up. The load level is something that's readable can can 
> be used to have rsync slow itself down. Nice doesn't do the trick. Nice 
> helps - but even at nice +19 it still slows the system to a crawl when 
> backing up from one drive to another.

Is that is on AIX with 12 AS400 CPUs or the VMS SSI cluster?
Or is that a single CPU linux box with a 2.4.?? kernel?

> So - if rsync could watch the load levels and pause every now and then 
> to put a little space between disk access at high load levels it would 
> make it a lot friendlier to the system. The reason nice doesn't work is 
> that once the system call is made to access the disk - nice doesn't apply.

What load levels?  Do you have some nice C code that can do
that for ALL the platforms without misreading?

This is what process and i/o schedulers are for.
Maybe you should contact the people responsible for whatever
kernel it is you are running.

> jw schultz wrote:
> >On Tue, Feb 17, 2004 at 03:16:32PM -0800, Marc Perkel wrote:
> > 
> >
> >This is what process and i/o schedulars are for.
> >
> >In most cases rsync is i/o bound.  Either disk or network.
> >That means it spends most of its time sleeping already.
> >This becomes increasingly true as the performance gulf grows
> >between CPU and that of memory, disk and network.
> >
> >Perhaps you have a suggestion for defining what constitutes
> >high load and how to determine that on all the different
> >platforms?  Hint: load average is meaningless.

	J.W. Schultz            Pegasystems Technologies
	email address:		jw at pegasys.ws

		Remember Cernan and Schmitt

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