Introduction to Lua-Land CPU Flame Graphs

Aug 31, 2020 18 mins read Posted by Yichun Zhang  (updated Jan 4, 2022)

• What is a Flame Graph
• Simple Lua samples
• Complicated Lua applications
• Sampling overhead
• Safety
• Compatibility
• Other types of Lua-land Flame Graphs

Memory Fragmentation in OpenResty and Nginx's Shared Memory Zones

Aug 10, 2020 9 mins read Posted by Yichun Zhang  (updated Jan 2, 2022)

• An empty zone
• Filling entries of similar sizes
• Deleting odd-numbered keys
• Deleting the keys in the first half
• Mitigating Fragmentation

How OpenResty and Nginx Shared Memory Zones Consume RAM

Aug 4, 2020 13 mins read Posted by Yichun Zhang  (updated Jan 4, 2022)

• Slabs and pages
• What is allocated is not what is paid for
• Fake Memory Leaks
• HUP reload

The Wonderland of Dynamic Tracing (Part 4 of 7)

Jun 27, 2020 7 mins read Posted by Yichun Zhang  (updated Dec 20, 2021)

This is Part 4 of the series “The Wonderland of Dynamic Tracing” which consists of 7 parts. I will keep updating this series to reflect the state of art of the dynamic tracing world. Read more...

The Wonderland of Dynamic Tracing (Part 3 of 7)

Jun 26, 2020 11 mins read Posted by Yichun Zhang  (updated Jan 2, 2022)

• Applications of SystemTap in Production
  • Case #1: Slow Debugging Code Left in Production
  • Case #2: Long request latency outliers
  • Case #3: From Network Issues to Disk Issues
  • Case #4: File Handle Cache Tradeoffs
  • Case #5: Compiled Regex Cache Tuning

The Wonderland of Dynamic Tracing (Part 2 of 7)

Jun 25, 2020 8 mins read Posted by Yichun Zhang  (updated Jan 4, 2022)

• DTrace
• SystemTap
• DTrace and SystemTap

The Wonderland of Dynamic Tracing (Part 1 of 7)

Jun 24, 2020 11 mins read Posted by Yichun Zhang  (updated Jan 2, 2022)

• Dynamic Tracing
• What It Is
• Too Good to be True?
• How it Works
• Still Having Doubts?
• The Advantages of Dynamic Tracing

How OpenResty and Nginx Allocate and Manage Memory

Jan 21, 2020 10 mins read Posted by Yichun Zhang  (updated Jan 4, 2022)

• On The System Level
• On The Application Level
• For Traditional Nginx Servers

The LuaJIT GC64 Mode

Jan 7, 2019 15 mins read Posted by Yichun Zhang  (updated Jan 4, 2022)

• The Old Memory Limit
  • When Hitting The Memory Limit
  • The Memory Limit Is Per Process
  • GC-Managed Memory
  • Memory Allocated Outside GC
  • Extending The x64 Mode to The 4 GB Limit
• The New GC64 Mode
  • How to Enable The GC64 Mode
  • Performance Impact
  • Debugging and Profiling Tool Chains