1. Lightweight Remote Procedure Call BRIAN N. BERSHAD THOMAS E. ANDERSON EDWARD D. LAZOWSKA HENRY M. LEVY Presented by Wen Sun

2. Overview What is LRPC? Why LRPC? Design and Implementation of LRPC The performance

3. What is RPC? Cross-Machine RPC Cross-Domain

4. What is LRPC? LRPC is a communication facility designed & optimized for cross-domain communication in the same machine.

5. Overview What is LRPC? Why LRPC? Design and Implementation of LRPC The performance

6. Why LRPC? “In existing RPC systems, cross-domain calls are implemented in terms of the facilities required by cross-machine ones”

7. Cross-domain dominates !

8. Cross-domain is simple ! Most frequent case: less than 200 bytes

9. Cross-Domain RPC Performs bad !

10. Causes of Overhead in RPC Stub overhead the caller and receiver are on the same kind of architecture, no need to marshal parameters and results into an intermediate, architecture independent representation Simple stubs (simple model of control and data transfer)  Message buffer overhead (four copy operation) both are in the same physical memory space LRPC only has one time copy from the client stub to A-stack both are in the same physical memory space Message transfer No message transfer in LRPC ! A-stack ! Dispatch

11. Causes of Overhead in RPC Access validation (validate send and return) LRPC doesn’t validate the return Scheduling Context switch Avoid context switch on multi-CPU by using caching domain on idle processor

12. Overview What is LRPC? Why LRPC? Design and Implementation of LRPC The performance

13. Design and Implementation Trap to Kernel Execute procedure and copy results Client User stub Server Kernel stub UpcallReturn (trap) A A stack Copy args Borrowed from Rizal Arryadi’s powerpoint (winter 2005)

14. Binding Server clientkernel Clerk interface Server name +interface Import call notifyPDL Biding project (key) + A-stack list Linkage record + A-stack

15. Calling Client Client Stub Kernel Server Stub Call Into (1)Get an A- stack (2)Copy arguments into A-stack (1)verifies binding, procedure ID, A- stack (2)locate the correct PD & linkage (3)ensures that no other thread using A-stack/linkage pair (4)Records caller’s return address and current stack pointer in the linkage (5)Pushes linkage onto top of stack of linkages kept in thread’s control block (6)Finds E-stack in the server’s domain (7)Updates thread’s user stack pointer to run off the new E- stack (8)Reloads processor’s Virtual Memory registers with those of the server domain (1)Copy immutable args from A-stack to a new region (2)Call server procedure, server executes (3)Copy return value into A- stack Trap (Binding Object, AS pointer, procedure ID) Upcall into Trap back Return result

16. Overview What is LRPC? Why LRPC? Design and Implementation of LRPC The performance

17. The performance (I) Roughly three times faster than SRC RPC

18. The performance (II) 21 = 18 ( client stub) + 3 (server stub) 27 (binding validation + linkage management)

19. The performance (III) lock contention !

20. Overview What is LRPC? Why LRPC? Design and Implementation of LRPC The performance