[openib-general] [kDAPL]How to register a vmalloc() allocated buffer

[Caitlin Bestler]

openib-general-bounces at openib.org wrote:
> On Tue, Dec 06, 2005 at 08:52:13PM +0800, Ian Jiang wrote:
>> Hi James,
>> You are always so kind!
>> Now I have a question about reading a buffer of a application in
>> user space. Is it the only way to use the uDAPL?
>> I used to have an idea like this:
>> The application in user space gives the virtual start address and
>> length of its data buffer to a kernel module program. This kernel
>> program acts as a application of the kDAPL and registers the user
>> space data buffer with the kDAPl,
> 
> Ian,
> If you are doing this with OpenIB, my advice is to NOT start
> with kDAPL.
> AFAICT, kDAPL is going away once any dependencies on it are resolved.
> And it's clearly not going to be pushed to kernel.org source trees.
> ISTR Dan Bar Dov wrote iSER was no longer dependent on kDAPL
> but not sure if that was the only module.
> 
> 
>> then request a RDMA read operation to complete the data transferring.
>> But I think it is not feasible after getting your last reply. Am I
>> right? Please give some suggestion and thanks very much!
> 
> In general, a kernel module can map a user space address to a
> "DMA Address". OpenIB code has interfaces to register the
> "DMA Address" with the IB card.
> 


kDAPL will still be of value for applications that want to minimize
their dependencies on the OS while still operating in kernel space
(but obviously not as part of *the* kernel).

However, agenting user-mode buffers is going to get very OS
specific, so this application doesn't seem to be one that
would benefit from kDAPL.