adding rsockets support into JDK

[Alan Bateman]

On 05/06/2018 07:17, Lu, Yingqi wrote:
> Hi All,
>
> Here is the version #4 of the patch
> http://cr.openjdk.java.net/~ylu/8195160.04/
>
> In this version, I have changed:
>
> 1. Remove jdk.net.RdmaSocketImplFactory.
> 2. Remove the inheritance from SocketChannelImpl/ServerSocketChannelImpl, replace it with SocketChannel/ServerSocketChannel.
> 3. Remove unnecessary setters from SocketImpl.
> 4. Override accept method to the ServerSocket returned by jdk.net.openServerSocket.
> 5. Add a small comment to PollSelectorImpl.poll method
> 6. Clean up a little in Lib-jdk.net.gmk
>
> I am still working on creating all the test cases. Do we need to replicate all the tests from both Socket/ServerSocket and SocketChannel/ServerSocketChannel, or we only need to pick up a subset of the cases?
>
> Please review the patch and let me know your feedback and comments.
>
For tests then I think we should have a basic set of tests that exercise 
each of the elements in the API. For each socket and channel type then 
each of the methods in the API should be exercised. There are several 
new socket options so they should be exercised too. So a good start is a 
maintainable set of unit tests. I don't think you should be concerned 
with duplicating all the existing tests as many of those tests are 
regression tests or stress specific areas where there were bugs in the past.

In general, I think testing is going to be a challenge for this feature 
as it needs commitment to maintain the infrastructure needed to test 
this feature and then running the tests at each release. When we added 
the SDP support, it required maintaining a set of machines with 
Infiniband HCAs and running the tests on a regular basis. I assume 
something similar will be needed here.

When developing the jtreg tests then it's important that don't fail on 
systems without RDMA hardware. For SDP, the tests checked for 
/proc/net/sdp and would pass silently when not present. I hope there is 
something easy to check for rsockets.

One thing that isn't clear to me is whether communication between using 
sockets on the same machine, using an address plumbed to an RDMA 
interface, will use the network or not. I guess I'm asking if you are 
thinking about functional testing with two or more machines, I assume 
you will at least be doing some of that when getting performance data 
and comparing it to TCP or SDP connections.

On the build changes, then one thing that would be useful to know is 
whether librdmacm is included in all distributions. If someone is 
building on say Ubuntu will they need to install an additional package 
installed. I bring this as we may need to do a bit more on the build to 
probe for the library. In other areas, at least in the past, we've had 
to resort to dynamic linking (dlopen/dlsym). I'm sure we should do that 
here, instead I'm just wondering whether the rsocket support will be 
compiled in when there it is not present on the build machine.

I skimmed quickly through the webrev and I think it's looking quite 
good. RdmaNet defines only static methods so I don't think it needs to 
extends Net. There is more to do on the javadoc for the new methods, 
also RdmaSocketOptions. I can help out on that when the time comes.

-Alan.