[ofw] Which API to use for IB project

[Thomas Peiselt]

Hi again,

after playing around with libibverbs for a day and a half, I'm going
to give uDAPL a try. The dapl specification is far superior to any
documentation I found for libibverbs or winverbs, and all else being
equal the portability and implementation effort determine the winner
:-).

thanks again to everyone contributing

Thomas

On Wed, Aug 5, 2009 at 6:14 PM, Sean Hefty<sean.hefty at intel.com> wrote:
>>1. latency
>>2. cpu load
>>3. low porting effort to linux compute nodes
>>4. implementation effort
>>
>>Latency is crucial, porting / implementation effort is just nice to have.
>
> For latency, really any of the RDMA APIs (winverbs, IBAL, ND,
> libibverbs/librdmacm, uDAPL) will work well.  The data path operations for any
> of these calls is relatively thin.
>
> For CPU load, IBAL, libibverbs/librdmacm, and uDAPL allocate additional system
> threads.  Again, the overhead is small in each case, but depending on how the
> interface is used, you may see additional latency, in particular with event
> processing, like CQ notifications.
>
> For portability, uDAPL and libibverbs/librdmacm are available on both Windows
> and Linux.  uDAPL abstracts everything, whereas libibverbs does expose some OS
> specific structures, like fd's on Linux.  If you keep to the libibverbs API, the
> code should be easily portable.  However, if you touch the OS specific
> structures, more work would be required to port, but you can also optimize
> somewhat for each OS.  This is how uDAPL is coded.
>
> - Sean
>
>