ECOMP an Erlang Processor Robert Tjrnstrm Ericsson Radio

ECOMP - an Erlang Processor Robert Tjärnström, Ericsson Radio Peter Lundell, Ericsson Telecom

Outline n n n Why an Erlang Processor The Architecture Run-Time System Prototype Results

What Is an Erlang Processor n A (micro) processor dedicated for execution of Erlang. • Executes compiled Erlang code.

Why a Dedicated Erlang Processor n n Increased use of Erlang Eliminating Performance and Power Dissipations Concerns • Low Power Important in Embedded Control n n Simplify use of Erlang for Embedded Control Eliminate cost for Real-Time Operating System • Provide run-time functionality

Power Dissipation in Processors n Factors Increasing Power Dissipation • • n Increasing functionality Less efficient code Less efficient languages Increasing speed requirements Factors Decreasing Power Dissipation • • • Lower supply voltages Scaled down mfg. processes Increased level of integration

Instruction Set Architecture n Optimized for Execution of Erlang Code • • • n Function calls, return from function Argument transfer list operations Register file management • Clean register file upon start of new function • No read/write-back of variables needed

Instruction Set Architecture n n n Supports processes Supports local scope Three sub-instructions in each machine instruction • Sub-instructions for garbage collections Tag Value

Processor Architecture n Much in common with conventional architectures n RISC LIW Harvard Pipelined (3 -5 stages) Fetch Decode Reg-File Execute No complex (advanced) features • • • Data Not super-scalar No OOO-execution or speculative execution No branch-prediction (but will be added) Mem unit • • Program

Processor Architecture n Real-time garbage collection • GC performed concurrently in HW • Currently supports one element size n n n HW supported process-switching (~20 cycles) Currently 1 process-queue, (may have more) Clock-cycle limit for each process (Basic type checking) (Prepared for Multi-Threading)

Run-Time Functionality n n n Switch, Spawn, Send, Message-queue handling, Catch/Throw, Time-out External io, Atom-handling, Registered processes Implemented in machine code Built-ins (e. g. , element) Standard Libraries (e. g. lists, ETS)

Prototyping n n n HW model of the processor (developed in Erlang) VHDL implementation & test bench FPGA based demonstrator (VHDL-code)

Prototyping II • PCI Board with Xilinx 40150 FPGA and 4 banks of 2 MB SRAM each • Board has PCI bridge (slows down communication)

Prototyping III n Using a PC (NT) to host the board. • Board driver routines only available for Win NT n Messaging between Erlang-host to Erlangboard is accomplished thru a dynamically loadable driver (DLL). • 7 us / message on average n n The external Erlang format is used for comm between board and host. IO processes are running on both board and host.

Performance n n About 3 -4 lines of machine code per Erlang line An approximate speed-up of a factor 30 can be seen • measured per use of clock cycles n Tested a larger example • Call Control. 16 KLOC. (714 k dump) • Increasing performance while decreasing power with more than order of a magnitude

Near Future Activities n n Compiler Improvements Product integration's • Distributed control node, e. g. , multi-processor execution. n n n Full-Scale Version. Multi-threaded Processor. Prepare for Silicon Implementation.