Re: SCSI driver for VMware's virtual HBA - V5.

[Alok Kataria <akataria@vmware.com>]

On Tue, 2009-10-13 at 15:00 -0700, Chris Wright wrote:
> * Alok Kataria (akataria@vmware.com) wrote:
> > On Mon, 2009-10-12 at 22:37 -0700, Chris Wright wrote:
> > > > +     pvscsi_template.can_queue =
> > > > +             min(PVSCSI_MAX_NUM_PAGES_REQ_RING, pvscsi_ring_pages) *
> > > > +             PVSCSI_MAX_NUM_REQ_ENTRIES_PER_PAGE;
> > > > +     pvscsi_template.cmd_per_lun =
> > > > +             min(pvscsi_template.can_queue, pvscsi_cmd_per_lun);
> > > 
> > > When/how are these tunables used?  Are they still useful?
> > 
> > cmd_per_lun, is a commandline parameter.
> 
> Actually I meant how is a user supposed to use these?  They looked to me
> like tunables that were part of developing a driver that may not be
> needed any longer.  
> What are the right values, what are the tradeoffs,
> etc?  Or should they just be removed?

The defaults are the right values, and though a normal user won't change
those in practice (he can if he wants to by passing values during
insmod), a developer working on performance tuning can use it. 

So I would like to keep these tunables around as it helps any future
performance work. 

Thanks,
Alok

> 
> thanks,
> -chris