Re: [Qemu-devel] [RFC PATCH RDMA support v4: 09/10] check for QMP string and bypass nonblock() calls

[Paolo Bonzini]

Il 19/03/2013 14:08, Michael R. Hines ha scritto:
> On 03/19/2013 05:23 AM, Paolo Bonzini wrote:
>>
>> Yes---this is a separate patch.  Apologies if you had the if(fd != -1)
>> before. :)  In fact, both the if(fd != -1) and the
>> if(!migrate_use_rdma(f)) are bad, but I prefer to eliminate as many uses
>> as possible of migrate_use_rdma.
> I agree. In my current patch I've eliminated all of them.

Very nice.  It remains to be seen how many are replaced by checks on the
QEMUFileOps :) but it cannot be worse!

>> Does librdmacm support non-blocking operation, similar to select() or
>> poll()?  Perhaps we can add support for that later.
> 
> Yes, it does, actually. The library provides what is called an "event
> channel".
> (This term is overloaded by other technologies, but that's OK).
> 
> An event channel is a file descriptor provided by (I believe) the rdma_cm
> kernel module driver.
> 
> When you poll on this file descriptor, it can tell you all sorts of things
> just like other files or sockets like when data is ready or when
> events of interest have completed (like the completion queue has elements).
> 
> In my current patch, I'm using this during
> "rdma_accept_incoming_connection()",
> but I'm not currently using it for the rest of the coroutine on the
> receiver side.

Ok, this can be added later.

Paolo