Adrian McMenamin wrote:
> On 14/12/2007, Tejun Heo <htejun@gmail.com> wrote:
>> Hello,
> 
>> There just isn't much room for maneuver w/ just one segment.  Large
>> contiguous memory region isn't too common these days.  That said, there
>> was a bug recently spotted by Mark Lord which made contiguous memory
>> regions even rarer.  Which kernel version are you using?
>>
> 
> Bang up to date latest git, ie -rc5-gitX
..

Not in -git yet, but it is in -mm.
Attached here for your convenience.

>>> Is that right? What is the best way to go here?
>> If you can spare some memory and cpu cycles, preparing a contiguous
>> buffer and staging data there might help.  It will eat up some cpu
>> cycles but it won't be too much compared to PIO cycles.
>>
> 
> OK, I'll try it
..

That's probably your best bet, even though it will mean copying
to/from your big bounce buffer with each I/O.

The code could be clever, I suppose, and only bounce when the supplied
I/O region is smaller than XXX pages.

Cheers