Subject: Re: Throttling IO Requests in NetBSD via Congestion Control
To: Jason Thorpe <>
From: Thor Lancelot Simon <>
List: tech-kern
Date: 12/01/2006 15:53:37
On Mon, Aug 21, 2006 at 02:15:07PM -0700, Jason Thorpe wrote:
> On Aug 21, 2006, at 12:47 PM, Thor Lancelot Simon wrote:
> >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?
> There's another reason to implement congestion control, as posited by  
> Bill Sommerfeld some years ago on this list.. and that is to ensure  
> that pages are dirtied (by writing to files) no faster than they can  
> be cleaned (more or less -- obviously, there is a little more too it  
> than that :-)

Isn't that exactly what I'm asking about?  "Congestion control" that
puts processes to sleep in a way that is *unrelated* to the ability of
the underlying disk to clear writes seems completely insane.