Hi

On Thu, Oct 19, 2006 at 03:40:20PM +1000, Andrew Reilly wrote:
> On Thu, 19 Oct 2006 00:01:53 +0200
> Reinoud Zandijk <reinoud@netbsd.org> wrote:
> > The syncfs syncer uses a different set of lists but yes, it too has the 
> > same problem with the lists.
> 
> I've never looked at the code, but I would have thought that
> there would be some sort of block-sorting/elevator-algorithm step
> in between "this list of blocks need to go to disk" and "disk
> drive: seek to xyz; write blocks nnn to nnn+m".  Isn't there?
> 
> If there is, then this reversal probably doesn't matter much, if
> all it does is pessimize an in-memory sort.

Well there is some sort of disc queue sorting going on at the disc 
interface driver level but thats a peep-hole optimalisation that only works 
for some sanity when accessed by multiple processes and asynchronous writes 
from one processes.

For synchronous writes this peep-hole optimalisation is not relevant since 
it will wait for each write to complete before it issues a new one.

With regards,
Reinoud