Subject: Re: Disk scheduling policy (Re: NEW_BUFQ_STRATEGY)
To: None <>
From: Jason Thorpe <>
List: tech-kern
Date: 12/01/2003 17:00:23
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On Dec 1, 2003, at 4:56 PM, Thor Lancelot Simon wrote:

> Unfortunately, this requires modifying every disk driver to handle
> uber-bufs instead of bufs, no?  It's highly similar to the change
> that BSDI made long ago to chain buffers together through a pointer
> in struct buf -- we could have whacked pagemove() much earlier if
> we picked up that change, but we didn't because of the changes it
> would have required in all of the disk drivers.

Yes, it would require a change to disk controller drivers (not disk 
drivers; they enqueue/dequeue, but don't really "process" the bufs).  
But is that really so horrible?

See what I said about adding a bus_dmamap_load_buf(); we could add this 
API call, and then such drivers would automatically pick up additional 
enhancements to the buf data representation mechanism.

         -- Jason R. Thorpe <>

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