Application Performance Overview
- 2. APPLICATION PERFORMANCE WHAT CAN GO WRONG? WHERE CAN IT GO WRONG? HOW TO FIX IT
- 3. Performance Bottlenecks Database Code Memory I/O and APIs Front End
- 4. Database Performance Indexes – not enough Indexes – too many! Index cache Query cache Query complexity Nesting Queries
- 5. Indexes Not enough indexes hurts read performance Too many indexes hurts write performance Covering indexes? Index hash size
- 6. Index Cache MySQL has separate index caches for MyISAM and InnoDB PostgreSQL allows tuning of index hash tables MySQL does not – keep hashes small if possible
- 7. Query Complexity SQL is a programming language too! Nested SELECTS EXPLAIN / EXPLAIN ANALYZE Query Optimiser or not Prepare/Execute
- 8. Code Performance PHP is an interpreter with an opcode cache NOT a compiler! Java is a bytecode compiler with a JIT Ruby/Python and Perl have opcode caches but are interpreted languages.
- 9. Code Performance Hogs eval() is evil() system() or popen() Closures/Lambda Functions Routing Crypto / Hash functions – be aware of what is efficient and what is not API calls
- 10. Memory The Thing King! (search it on google, written in 1972) Large blocks take less effort than small blocks malloc() is slow, but probably handled for you if you do things correctly All of this applies to caching. Cache large chunks not small ones.
- 11. I/O and APIs TCP calls require 3 packets SYN, ACK, SYN/ACK Before any data is sent API calls that require recursion: DNS, printing (IPP), SLC, anything involving clustering
- 12. Front End Javascript is an Interpreted Language No Bytecode Compiler No JIT Compilation (most browsers)
- 13. Javascript Performance Issues Compression Encryption Packet Decomposition (esp XML) Computation
- 14. How to Fix It Performance Testing – jMeter xdebug/kcachegrind Round trip time testing – Firebug
- 15. Caveats Don't move the problem elsewhere Don't create one problem to solve another one Background tasks take time too Spread the load that's causing the issue – network, I/O, CPU, memory, database