News CXL 3.0 Debuts, Wins CPU Interconnect Wars

[Admin]

The Compute eXpress Link (CXL) consortium today unveiled the CXL 3.0 specification, bringing new features like support for the PCIe 6.0 interface, memory pooling, and more complex switching and fabric capabilities to bear.

CXL 3.0 Debuts, Wins CPU Interconnect Wars : Read more

 

[cmccane]

CXL gets us closer to supercomputer interconnects like ccNUMA from SGI. Intel has been promising this type of tech for many years but it never materialized. It would have a significant impact on hyperscalers going forward. Today, in terms of RAM and processor scaling, every server is an island. Infiniband gave us RDMA but it was convoluted and not fast enough. You will always be dealing with stranded capacity when every server is an island. What I call Single Image Multi Server could become reality with CXL. That is a single Linux or Hypervisor image that runs across all servers in a rack. Individual app or VM performance on such a platform would still require placement tech to keep apps on Cores near their RAM. For microservices we could see communication happening over CXL instead of ethernet. Dynamically allocated centralized memory pools could also become reality. That would change up a typical 52 RU rack layout to include some RU’s dedicated to all-RAM servers so we could see such a thing as a RAM server and of course someone (not me) would coin the term Software Defined Memory.

 

[abufrejoval]

While your positive outlook gladdens my heart, my mind keeps reminding me, that Linux is an absolutistic disk operating system, which doesn't understand anything except CPUs, DRAM and block storage. Networks have been grafted on to a certain degree, but things like dynamic allocation and de-allocation of resources, heterogeneous computing devices or accelerators, dynamic reconfiguration of PCIe or CXL busses or meshes or just plain cooperation with other kernel instances with proper delegation of authority etc. just never were part of Unix, not even Plan-9.

So while the hardware is going there in leaps and bounds, I have very little hope Linux (neither as OS nor as hypervisor), Xen or any other hypervisor is anywhere ready to deal with all that.

Perhaps some cloud vendors will be able extend their proprietary hypervisors to take advantage of these things, but that doesn't bring that technology any closer to me.