Re: [rdiff-backup-users] Remote nice level

[Scot Wilcoxon]

> I am wondering if there is a way to run the remote rdiff-backup daemon
> in nice 19, for example, to reduce the stress it puts on the server.

If someone adds remote resource controls, I suggest controls for both CPU
priority and a nap time.
* nice() - CPU priority - is helpful on CPU-bound systems.
* sleep() - a forced delay - will throttle both CPU and I/O activity.
* I/O block size - about how many bytes of I/O between sleep().

Unfortunately, UNIX systems don't have a standard I/O throttling tool. 
But if an optional sleep() delay is added inside major loops, interference
on I/O-bound systems can be reduced.

I suggest that one sleep() be invoked after a certain number of bytes have
been transferred.  Keep track of the size of files which are being read,
and an estimate of the number of bytes involved in directory
manipulations.  Use that byte transfer count to trigger a sleep period
regularly -- but it's probably best to process an entire file, so after a
large file it might be necessary to sleep for more than one of the
configured nap times.