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Algorithms of linux memory management (simplified) - 1

G
Gokul Vasan

Some not so conspicuous, however performance sensitive algorithms in Linux Memory management is tried to be simplified in this slide

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Algorithms of Linux Memory Manager (Simplified) L J GOKUL VASAN
Watermark Working In Linux Detriment: Statically defined. Almost, whole memory needs to be filled to start reclamation. Could cause I/O pressure. Reclamation could cause false positives, leading to thrashing. Triggers page replacement. Defines aggression of the replacement policy. Are per zone free list's waypoint. Represented as count of free pages.
Swappiness variable in Linux scan rate Detriment: Ambiguity in semantics of variable. Global variable that effects the whole node.
OOM in Linux Kills the process with highest OOM badness. Detriment: oom_score_adj : Admin or system developer has little or no clue on tuning this variable per process. Might kill a process thats of importance to system. Does not provide right statistics for developers debugging.
RMAP [Reverse Mapping] Opposite to Memory Mapping. Traverses the PTE of a page and cumulates hardware reference count.

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Algorithms of linux memory management (simplified) - 1

  • 1. Algorithms of Linux Memory Manager (Simplified) L J GOKUL VASAN
  • 2. Watermark Working In Linux Detriment: Statically defined. Almost, whole memory needs to be filled to start reclamation. Could cause I/O pressure. Reclamation could cause false positives, leading to thrashing. Triggers page replacement. Defines aggression of the replacement policy. Are per zone free list's waypoint. Represented as count of free pages.
  • 3. Swappiness variable in Linux scan rate Detriment: Ambiguity in semantics of variable. Global variable that effects the whole node.
  • 4. OOM in Linux Kills the process with highest OOM badness. Detriment: oom_score_adj : Admin or system developer has little or no clue on tuning this variable per process. Might kill a process thats of importance to system. Does not provide right statistics for developers debugging.
  • 5. RMAP [Reverse Mapping] Opposite to Memory Mapping. Traverses the PTE of a page and cumulates hardware reference count.