Subject: Re: Throttling IO Requests in NetBSD via Congestion Control
To: Sumantra Kundu <>
From: Thor Lancelot Simon <>
List: tech-kern
Date: 08/21/2006 15:47:43
On Mon, Aug 21, 2006 at 02:40:38PM -0500, Sumantra Kundu wrote:
> > In the limiting case, that sets
> >an upper bound on output rate, regardless of other demand. That would 
> >allow other
> >processes (which would generate read requests) to make more requeasts.
> >
> + Since we do not correlating the rate of read requests, putting
> processes to sleep, independently, indeed places an upper bound on the
> write throughput.

I guess I'm confused.  How, exactly, do we measure the maximum aggregate
operations/sec throughput of the disk?  There should be no upper bound
on the write throughput unless we reach that number, because writers
should never be put to sleep.  Is that not the case?

This sort of issue is one reason why I suggested monitoring per-request
latency as the congestion metric, rather than merely using raw requests/sec