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Memory Measurements Complexities and Considerations - Part 1

By RILEY ZIMMERMAN posted Thu July 01, 2021 06:14 AM

  

Memory Measurements Complexities and Considerations

Part 1: Buffers and (File Page) Cache

System caches use all available memory to optimize disk IO. Knowing which memory metrics count this usage in their stat is therefore crucial to proper memory analysis.

Going to the Library

File Page Cache

Memory Measurement Breakdown

Used vs Available Details (Advanced)

(meminfo) Buffers + Cached = Active(file) + Inactive(file) + Shmem
11,448 + 25,584,276 = 12,160,004 + 8,517,192 + 4,918,528 = 25,595,724
(meminfo) Buffers + Cached + SReclaimable = (free) buffers + cache11,448 + 25,584,276 + 4,789,196 = 11,448 + 30,373,472 = 30,384,920
kb_main_cached = kb_page_cache + kb_slab_reclaimable;
mem_used = kb_main_total - kb_main_free - kb_main_cached - kb_main_buffers;
mem_available = (signed long)kb_main_free 
- watermark_low
+ kb_inactive_file + kb_active_file
- MIN((kb_inactive_file + kb_active_file) / 2, watermark_low)
+ kb_slab_reclaimable
- MIN(kb_slab_reclaimable / 2, watermark_low);

System Examples

Monitoring, Tracking, and Analyzing the Data

Insights from the Data

System Memory Summary

To Be Continued…


#linux
#Kubernetes
#cache
#performance
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