Software Performance Analysis Using CodeAnalyst for Windows

1. Software Performance Analysis UsingCodeAnalyst for Windows Lei Yu Member Technical StaffSRDlei.yu@amd.com Advanced Micro Devices Sherry Hurwitz SW Applications ManagerSRDsherry.hurwitz@amd.com Advanced Micro Devices

2. Session Outline • Exploiting Performance Opportunities • Obvious Performance Potential • Hidden Performance Potential • Exposing Untapped Performance Potential • Analyzing Performance Improvement Trials • AMD CodeAnalyst Performance Analysis Tool • Capabilities of CodeAnalyst • Functionality of CodeAnalyst • Profile Capabilities • Thread Analysis • Pipeline Simulation

3. Obvious Performance Potential • Processor Architecture • x64 Processors • Extended Memory Addressing • Additional Registers • Deeper Execution Pipeline • Multi-Core Processors • Multiprocessing for the desktop system • Multiple processor platforms • 64-bit Windows® operating systems • Compiler optimization switches • Optimized libraries (for example AMD ACML)

4. Hidden Performance Potential • Efficient algorithms • Cache friendly memory access • Branch Prediction friendly conditionals • Parallel work through Threads • Object Synchronization

5. Expose Untapped Performance Potential • Profile your application with the AMD CodeAnalyst Performance Analyzer • Timer-based sampling - identify time consuming or frequently executed code possibly pointing to algorithm issues (Hot Spots) • Opteron and Athlon 64 processor performance events - evaluate the applications use of architectural features • Thread View - evaluate effective use of multiple processors • Pipeline Simulation - understand how data dependencies can stall the processor execution • Iterate - between profiling and code modifications testing if there are performance benefits

6. Analyzing Performance Improvement Trials

7. Capabilities of AMD CodeAnalyst • CodeAnalyst CAN: • Assist in optimizing your application • Identify program bottlenecks • Monitor and Analyze software performance • CodeAnalyst CANNOT: • Identify defects in your program (Profile a functioning stable application.) • CodeAnalyst RUNS ON: • Windows: WinNT, Win2K , WinXP, 64-bit Windows® operating systems

8. Key Functionality of AMD CodeAnalyst • Profiling • Timer-based sampling • Event-based sampling • Thread analysis • Execution Pipeline Simulation

9. Profile Capabilities • Low overhead system-wide profile • Timer-based profile: • 0.1 ms resolution on APIC enabled systems • 1.0ms resolution on APIC disabled systems • Event-based profile: • 32 AMD Athlon™ and AMD Athlon™ XP performance events • 78 AMD Opteron™ and AMD Athlon™ 64 performance events • Simultaneously profile up to 4 user selected performance events. • Profiles multiple processor systems up to 16 processor cores

10. Profile Analysis • Identifies all active Process Names, Process IDs, Thread IDs • Identifies the Process CPU affinity • Identifies performance event per CPU • Maps sample addresses to Process, Module, Function, Source Line, Assembly Instruction, Code Byte

11. Hierarchical Navigation of Data Views • System Data View • System Graph View • Module Data View • Module Graph View • Source View • Disassembly View Demo will show the details of each of these views and the navigation between the views.

12. Timer-based Profiling - the First Level of Analysis • Exposes areas of intense activity • Identifies the most likely suspects • Provides a sample distribution chart • Ability to drill down through several data views • View the source code on and around the sample • Algorithmic issues may be evident from the hot spot code • Hot spot code might suggest particular events to profile in next level of Analysis

13. Common Hot Spots • Loops • Large content and large loop counts are natural hot spots but not bad for performance • Small content with small fixed loop counts should be unrolled • Remove redundant constant calculations from inner loops, including from inner control structures • Long Logical Expressions in If Statements • Long data dependent expressions • Complicated Floating Point expressions

14. Event-based Profile - Second Level of Analysis • Useful Events to Identify Memory Issues • “Data Cache Access” and “Data Cache Misses” simultaneously • use the ratio of Misses to Access • Count Misaligned Data Reference • Useful Events to Identify Branching Issues • “Retired branch mispredicted” and “Retired taken branches” • use the ratio of mispredicted to branch taken

15. Examples of Memory Issues • Large data structures with variable size members not sorted by size • Use of pointer notation in manipulating large data arrays • Dereferenced pointer arguments inside a function • Large declarations of local variables declared randomly with respect to size • Memory buffers shared between threads

16. Examples of Branch Prediction Issues • Order of the expressions in compound branch conditions • Order of operands in Logical expressions • Large switch statements with noncontiguous expressions • Large switch statements cases out of order in respect to probability

17. Thread Analysis • Identities threads in the target application. • Shows Thread creation and termination • Monitors CPU affinity of each thread • Identifies Non-local memory access • Graphs thread activity on each CPU

18. Thread Analysis Data View

19. Pipeline Simulation Capabilities CodeAnalyst can simulate a user specified block of code on AMD microprocessors and provide cycle-precise execution info. Requirement: Defining a code block to simulate, requires the user to provide debug info for the target module. Limitation: • Cannot simulate instructions inside system space • Cannot simulate multi-thread

20. Some Assumptions in the Simulator • Assumes perfect memory subsystem • All Load/Store Micro-ops hit in the Data Cache • Assumes that 1 misaligned load = 2 back-to-back aligned loads (64-bit) • Assumes no cache bank conflicts • 100% Instruction cache hit rate • Assumes perfect branch prediction • Assumes all schedulers are of infinite size

21. Pipeline Data View

22. CodeAnalyst Simulation Analysis • User specifies Simulation configuration • User sets Trace Point Start, Trace point End, and trace trigger • Pipeline Data View • Pipeline stage • Penalty • Dependency • Delta completion • IPC • User can view Simulation History

23. Call to Action • Download CodeAnalyst • Improve Your Software!

24. Additional Resources • Web Resources at: • http://www.developwithamd.com • Download CodeAnalyst • Software Optimization Guide for AMD Athlon 64 and AMD Opteron • AMD64 Architecture Programmer's Manual Volume 1: Application Programming • AMD64 Architecture Programmer's Manual Volume 2: System Programming • AMD64 Architecture Programmer's Manual Volume 3: General-Purpose and System Instructions • AMD64 Architecture Programmer's Manual Volume 4: 128-Bit Media Instructions • AMD64 Architecture Programmer's Manual Volume 5: 64-Bit Media and x87 Floating-Point Instructions • http://www.devx.com • Optimizing Your C/C++ Applications, Part 1 & 2 • Whitepapers: • Porting and Optimizing Applications on 64-bit Windows for AMD64 Architecture, Winhec 2004 paper by Mike Wall