Re: [PATCH] Speed up the cdrw packet writing driver

[Lee Revell]

On Tue, 2004-08-24 at 17:47, Andrew Morton wrote:
> Peter Osterlund <petero2@xxxxxxxxx> wrote:
> > 
> > Why is it not nice? If the VM has decided to create 400MB of dirty
> > data on a DVD+RW packet device, I don't see a problem with submitting
> > all bio's at the same time to the packet device.
> 
> We also have a limit on the number of in-flight requests:
> /sys/block/sda/queue/nr_requests.  It defaults to 128.
> 
> Are you saying that your requests are so huge that each one has 1000 BIOs? 
> That would be odd, for an IDE interface.
> 

This defaults to 8192 on my (IDE) system.  IIRC this value is larger if
48-bit addressing is in use (drive size > ~128GB).  It does not seem
right to me that the size of your hard drive should dictate the amount
of I/O allowed to be in flight.

Lee

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