Re: Suspend/Resume

[James Bottomley <James.Bottomley@SteelEye.com>]

On Sun, 2005-05-08 at 18:21 +0200, Jens Axboe wrote:
> On May 8, 2005, at 5:53 AM, James Bottomley wrote:
> > The patch looks fine as far as it goes ... however, shouldn't we be
> > spinning *internal* suspended drives down as well like IDE does  
> > (i.e. at
> > least the sd ULD needs to be a party to the suspend)?  Of course  
> > this is
> > a complete can of worms since we really have no idea which busses are
> > internal and which are external, although it might be something that
> > userland can determine.
> 
> I'm not sure I know what you mean by 'internal suspended drives' that  
> aren't spun down? For every device known on the sata "bus", we do the  
> standby routine.

I mean that at the moment, the suspend code doesn't seem to spin down
any SCSI drives.  However, if it did we'd need to distinguish between
drives that uniquely belong to us (i.e. drives that are internal to the
system) and drives that are external on a shared bus for which we'd
annoy other systems if we spun them down.

> There is room for improvement for software suspend, notably it is  
> extremely annoying that we cannot tell the difference between  
> 'freeze' and 'suspend' currently, this adds overhead for suspend-to- 
> disk both in time spent and actual drive wear due to an excessive  
> spin down+up cycle.
> 
> > P.S.  I noticed the gratuitous coding style corrections ...
> 
> Heh woops, I usually don't sneak those in with other changes. I think  
> this one got in because I actually had another change there that I  
> later reverted.

;-)

James