Re: CVS commit: src/sys/dev/scsipi

[Frank Kardel <kardel%netbsd.org@localhost>]

Erik,

I agree with this very much. Actually I have been toying around with 
this idea
quite some time. My thoughts where to build a sysctl tree for all scsi 
commands
with their default values and another level of sysctl timeout nodes 
where the
vendor and device name or driver name is part of the hierarchy to 
override timeouts
for some commands. Solaris has, I believe some of those knobs.

So far I didn't manage to invest the time for a complete implementation.

But maybe, as we currently are only suffering with changers, it would be 
sufficient
to add a single timeout knob for the changers. Like 
dev.ch0.scsi_timeout=300 (s)

How about that?

Frank

On 08/10/13 00:14, Erik Fair wrote:
> On Aug 9, 2013, at 12:58 , Frank Kardel <kardel%netbsd.org@localhost> wrote:
>
> > Module Name:    src
> > Committed By:   kardel
> > Date:           Fri Aug  9 19:58:44 UTC 2013
> >
> > Modified Files:
> >         src/sys/dev/scsipi: ch.c
> >
> > Log Message:
> > bump command timeout to 5 minutes. several
> > types of changers (Overland PowerLoader, Dell
> > PowerVault) have been exceeding the 100 sec
> > limit aborting a perfectly (slowly) progressing
> > operation.
> Upon further reflection, I believe that this timeout value should be a 
> device-specific tunable parameter because there is such wide variation in 
> changer behavior/performance; perhaps by kernel config, or by sysctl(8) on a 
> per-device-node basis. Or some other mechanism you prefer.
>
> I believe that baking it into the kernel as a constant is not good design 
> because we'll just see another commit just like this one at some later date, 
> continuing to patch around the design problem.
>
>         Erik <fair%netbsd.org@localhost>