Is there a way to check or monitor the hit rate in EMP just like buffer pool in PolarDB？

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Summary

The question revolves around monitoring the hit rate in EMP (Enterprise Memory Pool), similar to the buffer pool in PolarDB, to quantify performance improvements. The user noticed a low Buffer Pool hit rate, leading to a large number of disk read operations and is looking for metrics to measure the hit rate for EMP.

Root Cause

The root cause of the issue is the lack of direct metrics to measure the hit rate for EMP, making it challenging to evaluate the performance improvement brought by enabling EMP. The key causes include:

  • Limited visibility into EMP’s internal workings
  • Insufficient metrics to quantify performance gains
  • Difficulty in comparing EMP’s performance to traditional buffer pool performance

Why This Happens in Real Systems

This issue occurs in real systems due to:

  • Complexity of modern databases: The increasing complexity of database systems, such as PolarDB, can lead to hidden performance bottlenecks
  • Lack of standardization: Different databases and storage engines, like EMP, may have unique performance characteristics and metrics
  • Evolution of storage technologies: The introduction of new storage technologies, such as EMP, can create new challenges for performance monitoring and optimization

Real-World Impact

The real-world impact of this issue includes:

  • Reduced performance: Low Buffer Pool hit rates can result in increased disk read operations, leading to reduced system performance
  • Increased latency: The lack of optimized EMP performance can cause increased latency and degraded user experience
  • Inefficient resource utilization: Inadequate performance monitoring and optimization can lead to inefficient resource utilization, resulting in wasted resources and increased costs

Example or Code (if necessary and relevant)

-- Example query to monitor Buffer Pool hit rate in PolarDB
SELECT 
  variable_name, 
  variable_value 
FROM 
  information_schema.global_status 
WHERE 
  variable_name IN ('Innodb_buffer_pool_reads', 'Innodb_buffer_pool_read_requests');

How Senior Engineers Fix It

Senior engineers address this issue by:

  • Implementing custom monitoring solutions: Creating custom scripts or tools to monitor EMP’s performance and hit rate
  • Utilizing database-specific metrics: Leveraging database-specific metrics and tools to quantify performance gains and optimize EMP configuration
  • Collaborating with database vendors: Working closely with database vendors to request new features or metrics to improve performance monitoring and optimization

Why Juniors Miss It

Junior engineers may miss this issue due to:

  • Lack of experience: Limited experience with complex database systems and performance optimization
  • Insufficient knowledge: Inadequate understanding of database-specific metrics and performance characteristics
  • Overreliance on standard tools: Relying too heavily on standard monitoring tools and metrics, rather than customizing solutions for specific use cases

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