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SubjectRe: disk head scheduling

Forgive me for jumping in late on this one - I have just one
observation. It isn't clear to me that it would work well to have a
single queue per device, at least in all cases. Some host adapters have
limits (sometimes in hardware, not just a driver limitation) on the
maximum number of outstanding commands, and it would take a bit of hacking
to find a way to pick commands from multiple queues in order to prevent
starvation. For host adapters that have no such limits, then a per-device
queue would work just fine.

-Eric


On Tue, 23 Mar 1999, Rogier Wolff wrote:

> Linus Torvalds wrote:
> >
> >
> > On Tue, 23 Mar 1999, Rogier Wolff wrote:
> > > >
> > > > This is what we do for block sizes, and it's a complete horror to maintain
> > > > and debug. Even worse: it forces us to have 8-bit minor and major numbers
> > > > forever.
> > >
> > > Nah! It is the device drivers responsibility to allocate enough
> > > space. So if a new SCSI disk driver notices 20 disks, and therefore
> > > wants 320 minors, it should allocate the array to be 320 entries.
> >
> > Umm..
> >
> > What if we have sparse minor numbers?
>
> Let me start by saying I agree completely. You convinced me in one
> go.
>
> Ehhmm. You're paraphrasing the paragraph that I had written below the
> one you quoted.
>
> Roger.
>
> --
> ** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2137555 **
> *-- BitWizard writes Linux device drivers for any device you may have! --*
> ------ Microsoft gives you Windows, Linux gives you the whole house ------
>
>
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