73 lines
2.5 KiB
C
73 lines
2.5 KiB
C
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// ss_release_policy_box.h - SuperSlab Release Policy Box
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// Purpose: Determine when to keep/release/decommit superslabs (Memory-Lean mode)
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// Box Theory: Single conversion point for superslab lifecycle decisions
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//
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// Responsibilities:
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// - Decide if a superslab should be kept (persistent) or released
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// - Execute decommit operations (MADV_FREE/MADV_DONTNEED) when lean mode enabled
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// - Respect DSO guard / fail-fast rules (never touch DSO memory)
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//
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// Design Philosophy:
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// - In FAST mode (default): Keep all superslabs (speed-first, persistent backend)
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// - In LEAN mode (opt-in): Release empty superslabs to reduce RSS
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// - Boundary: All decommit operations flow through Superslab OS Box (ss_os_madvise_guarded)
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// - Safety: DSO guard prevents touching .fini_array (Phase 17 lesson)
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//
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// Dependencies:
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// - ss_mem_lean_env_box.h (ENV configuration)
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// - madvise_guard_box.h (DSO-safe madvise wrapper)
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// - ss_os_acquire_box.h (stats counters)
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//
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// License: MIT
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// Date: 2025-12-17
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#ifndef HAKMEM_SS_RELEASE_POLICY_BOX_H
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#define HAKMEM_SS_RELEASE_POLICY_BOX_H
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#include <stdint.h>
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#include <stddef.h>
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#include <stdbool.h>
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// Forward declaration
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struct SuperSlab;
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typedef struct SuperSlab SuperSlab;
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// ============================================================================
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// Release Policy API
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// ============================================================================
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// Check if a superslab should be kept in memory (persistent backend)
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//
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// Returns:
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// - true: Keep superslab (FAST mode, or LEAN mode with budget remaining)
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// - false: Release superslab (LEAN mode, empty and over budget)
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//
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// Parameters:
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// - ss: SuperSlab to check
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// - class_idx: Size class (0-7 for Tiny)
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//
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// Thread-safe: Yes (reads ENV config, no shared state)
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bool ss_should_keep_superslab(SuperSlab* ss, int class_idx);
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// Attempt to decommit a superslab's memory (reduce RSS)
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//
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// What it does:
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// - If lean mode disabled: no-op (return immediately)
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// - If lean mode enabled: call madvise(MADV_FREE or MADV_DONTNEED)
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// - Respects DSO guard (skips if address overlaps DSO)
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// - Respects madvise guard (disables on ENOMEM)
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// - Updates lean_decommit counter on success
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//
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// Returns:
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// - 0: Success (or no-op if lean mode disabled)
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// - -1: Failed (DSO overlap, madvise error, etc.)
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//
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// Parameters:
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// - ptr: Start of memory region
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// - size: Size of memory region in bytes
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//
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// Thread-safe: Yes (no shared state mutations except atomic counters)
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int ss_maybe_decommit_superslab(void* ptr, size_t size);
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#endif // HAKMEM_SS_RELEASE_POLICY_BOX_H
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