Subject: Re: mp->mnt_vnodelist change
To: Manuel Bouyer <>
From: Thor Lancelot Simon <>
List: tech-kern
Date: 10/18/2006 15:02:44
On Wed, Oct 18, 2006 at 08:51:34PM +0200, Manuel Bouyer wrote:
> On Wed, Oct 18, 2006 at 08:34:46PM +0200, Reinoud Zandijk wrote:
> > [...]
> > 
> > Normal discs dont mind that but media like CD/DVD *hate* that and due to 
> > their nature, writing with decending adresses takes around 10 times as much 
> > time as writing ascending adresses if not more. In fact the current 
> > implementation is faster in synchronious mount rather than asynchronious 
> > mount for that reason.
> I think this can affect normal disks as well; e.g. hardware RAID controllers
> which have heuristics to detect sequencial writes.

I'm trying to understand this: are you saying that every time we walk the
vnode list to flush, we end up writing blocks in reverse order?

Why does writing the vnodes in the reverse order they were put on the list
cause the block orders to also be reversed?

If this is really true, it should be fixed for all disks.

  Thor Lancelot Simon	                           

  "We cannot usually in social life pursue a single value or a single moral
   aim, untroubled by the need to compromise with others."      - H.L.A. Hart