application needs fast access to physical memory

[Michael Ellerman]

On Wed, 2010-11-17 at 16:03 -0600, steven.lin at teradyne.com wrote:
> My application needs a fast way to access a specific physical DDR
> memory region. The application runs on an MPC8548 PowerPC which has an
> MMU. I've tried two approaches that are typical for Linux, mmap() and
> using a kernel module that implements read()/write() into this region
> and I'm finding that performance is very slow for both. It's a couple
> orders of magnitude slower than, for example, copying a large buffer
> from one place in the application's virtual memory to another place in
> the application's virtual memory.

The mmap() version should basically run at "full speed", at least once
you've faulted the address range in.

This specific DDR region isn't specifically slow is it ? :)

cheers
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