Power Profiling using Sim-Panalyzer Andria Dyess and Trey Brakefield CPE631 Spring 2005

Presentation Overview Introduction to Sim-Panalyzer Project Goals Current Status Future Work

What is Sim-Panalyzer? Developed by researchers at the University of Michigan and the University of Colorado Based on the SimpleScalar processor simulator Builds on Sim-Outorder Adds statistics for power estimation Compiled with gcc Runs in Linux environment

Estimating Power Consumption with Sim-Panalyzer User supplies a.cfg file which defines the CPU architecture A separate.cmd file specifies voltages, capacitance, and other values needed to calculate power consumption for each architectural element

Project Goals Become familiar with the Sim-Panalyzer software Add support for turning on and off the collection of power statistics Add support for power profiling Run simple simulations to test the new features

Sim-Panalyzer Software Environment Options database for registering command line options Stats database for managing performance statistics Register Update Unit (RUU) Load/Store Queue (LSQ) Pipeline stages: Fetch/Decode, Issue, Execution (out of order), and Commit

Project Goal #1: Start and Stop Flags for Simulation Stats Allows the user to profile specific sections of the test program (e.g. a single subroutine) The test program writes to a designated memory address to control collection of stats Simulator traps writes to this memory address and performs the appropriate action

Implementation Specifics Added a new command line option, “profiling: addr” Added code to watch for the specified memory address just before each store instruction is committed Overhead associated with this additional instruction (effective address calculation)

Implementation Specifics Added code around all statistics updating to check if statistics counting is on. Added code to Stats database to reset all of the statistics registered. Implemented the function calls needed to start, stop, dump, and reset stats in sim-profiling.h/c.

Sample Code (capturing a start_stop memory access) if (LSQ[LSQ_head].addr == start_stop_addr){ switch (/*value being written*/) { case 1 : profile_off();/* Stop counters */ break; case 2 : profile_on();/* Start counters */ break; case 3 : profile_reset(power_sdb);/* Reset counters */ break; case 4 : profile_dump(power_sdb, fd);/* Dump counters */ break;/* to output file */ }

Sample Code (resetting statistics) stat_reset_stat(struct stat_sdb_t *sdb, /* stat database */ struct stat_stat_t *stat,/* stat variable */ FILE *fd) /* output stream */ { struct eval_value_t val; switch (stat->sc) { case sc_int: *(stat->variant.for_int.var)=stat->variant.for_int.init_val; break;. default: panic("bogus stat class"); }

Sample Code (not counting statistics) #ifdef PROFILING if ( counting_on) #endif /* PROFILING */ { }

Project Goal #2: Power Profiling Allows user to get power statistics supplied by sim-panalyzer in slices Builds on work already done for project Goal #1. The simulator will watch the instruction count. When instruction count meets user-defined number, stats are stopped, dumped, reset, and restarted.

Implementation Specifics Added a new command line option, “profiling: inst” Add code to watch instruction count

Sample Code (profiling output) /* profiling? */ if ( sim_num_insn >= profile_inst_count ) { profile_iter++; fprintf(fd, "/n***** Profiling (%d) ******/n/n", profile_iter); profile_dump(power_sdb, fd); profile_reset(power_sdb); }

Project Status Command line arguments have been added and tested The stats database provides the ability to easily dump and reset stats  Most difficult task is finding the code that increments counters and adding a check for the flag (with out effecting the simulation).

Future Work Long-term goal is to develop “power monitoring counters” that can be implemented in future CPUs (similar to the performance monitoring counters that are common today) Expand profiling beyond the power profiling statistics alone.