SMP (Symmetric Multiprocessing)

Overview

The FreeWorld SMP (Symmetric Multiprocessing) system provides complete multi-core and multi-processor support with enterprise-grade features. It includes:

• SMP Core: Per-CPU data structures, CPU initialization, topology tracking
• CPU Detection: CPU enumeration, feature detection, vendor identification
• CPU Affinity: Process and thread CPU affinity management
• Load Balancing: Advanced load balancing across CPUs
• Per-CPU Runqueues: Isolated runqueues per CPU
• Inter-Processor Interrupts: IPI system for CPU communication
• CPU Hotplug: Dynamic CPU addition/removal
• NUMA Support: Non-Uniform Memory Access topology awareness
• Hyperthreading: Hyperthreading detection and management
• Frequency Scaling: SMP-enhanced CPU frequency scaling
• Power Management: Advanced CPU power management
• Scheduling Domains: Scheduling domain hierarchy and management

Components

1. SMP Core (smp_core.asm)

Location: kernel/smp/smp_core.asm

Core SMP infrastructure and per-CPU data structures:

Features

• Per-CPU data structures (CPU ID, APIC ID, runqueue, stack, etc.)
• CPU initialization and management
• CPU online/offline support
• CPU topology tracking (package, core, thread, SMT ID)
• BSP (Bootstrap Processor) identification

Key Functions

2. CPU Detection (cpu_detection.asm)

Location: kernel/smp/cpu_detection.asm

CPU detection and enumeration:

Features

• CPU enumeration using ACPI MADT or CPUID
• CPU feature detection (SSE, AVX, VMX, SVM, etc.)
• Vendor identification (Intel, AMD)
• Brand string detection

3. CPU Affinity (cpu_affinity.asm)

Location: kernel/smp/cpu_affinity.asm

CPU affinity management for processes and threads:

Features

• Process CPU affinity (set/get)
• Thread CPU affinity (set/get)
• 256-bit CPU mask support (32 bytes)
• Affinity clearing (allow all CPUs)

4. Load Balancing (load_balancing.asm)

Location: kernel/smp/load_balancing.asm

Advanced load balancing across CPUs:

Features

• CPU load tracking (0-100%)
• Automatic load balancing
• Task migration between CPUs
• Idle CPU detection
• Configurable balance intervals

5. Per-CPU Runqueues (per_cpu_runqueue.asm)

Location: kernel/smp/per_cpu_runqueue.asm

Isolated runqueues per CPU:

Features

• Per-CPU task lists
• Task enqueue/dequeue operations
• Runnable task counting
• Idle task management

6. Inter-Processor Interrupts (inter_processor_interrupts.asm)

Location: kernel/smp/inter_processor_interrupts.asm

IPI system for CPU communication:

IPI Types

• IPI_RESCHEDULE: Trigger reschedule
• IPI_CALL_FUNCTION: Call function on CPU
• IPI_TLB_FLUSH: Flush TLB
• IPI_STOP_CPU: Stop CPU
• IPI_NMI: Non-maskable interrupt
• IPI_KICK_CPU: Wake CPU

7. CPU Hotplug (cpu_hotplug.asm)

Location: kernel/smp/cpu_hotplug.asm

Dynamic CPU addition/removal:

Features

• CPU hotplug initialization
• Add CPU to system
• Remove CPU from system
• CPU preparation and cleanup
• Automatic task migration

8. NUMA Support (numa.asm)

Location: kernel/smp/numa.asm

NUMA topology awareness:

Features

• NUMA node detection from ACPI SRAT
• Distance matrix (local/remote)
• NUMA-aware memory allocation
• CPU-to-node mapping

9. Hyperthreading (hyperthreading.asm)

Location: kernel/smp/hyperthreading.asm

Hyperthreading detection and management:

Features

• Hyperthreading detection via CPUID
• Sibling CPU mapping
• APIC ID parsing (package, core, thread)

10. CPU Frequency Scaling (cpu_frequency_smp.asm)

Location: kernel/smp/cpu_frequency_smp.asm

SMP-enhanced CPU frequency scaling:

Features

• Per-CPU frequency management
• Frequency governors (performance, powersave, ondemand, conservative, userspace)
• P-state support
• MSR/ACPI integration

11. CPU Power Management (cpu_power_management.asm)

Location: kernel/smp/cpu_power_management.asm

Advanced CPU power management:

Power States

• C0: Active
• C1: Halt
• C1E: Enhanced halt
• C2: Stop clock
• C3: Deep sleep
• C6: Deep power down
• C7: Deeper sleep

12. Scheduling Domains (scheduling_domains.asm)

Location: kernel/smp/scheduling_domains.asm

Scheduling domain hierarchy and management:

Domain Levels

• SD_LEVEL_SIBLING: Sibling CPUs (same core, hyperthreads)
• SD_LEVEL_MC: Multi-core (same package)
• SD_LEVEL_NUMA: NUMA node
• SD_LEVEL_ALLNODES: All nodes

Integration

The SMP system is integrated into the kernel via kernel/smp/:

; In kernel initialization:
call smp_init              ; Initialize SMP system
call cpu_detection_enumerate ; Enumerate all CPUs
call runqueue_init         ; Initialize per-CPU runqueues
call load_balancing_init   ; Initialize load balancing
call ipi_init              ; Initialize IPI system
call numa_init             ; Initialize NUMA support
call hyperthreading_init   ; Initialize hyperthreading
call cpu_freq_smp_init     ; Initialize frequency scaling
call cpu_power_init        ; Initialize power management
call sched_domain_init     ; Initialize scheduling domains

Status: ✅ Integrated - Called during kernel initialization

Usage Examples

Get CPU Count

call smp_get_cpu_count
; EAX now contains number of CPUs

Get Current CPU ID

call smp_get_cpu_id
; EAX now contains current CPU ID

Set CPU Affinity

; Set process to run on CPU 0 only
mov rdi, process_ptr
mov rsi, affinity_mask  ; Bit 0 set = CPU 0
call cpu_affinity_set

Send IPI

; Send reschedule IPI to CPU 1
mov rdi, 1  ; Target CPU
mov rsi, IPI_RESCHEDULE
call ipi_send

Implementation Details

Per-CPU Data Structure

Each CPU has its own data structure containing:

• CPU ID and APIC ID
• Online/initialized flags
• Runqueue pointer
• Idle and current task pointers
• TSS, GDT, IDT pointers
• Kernel stack pointer
• NUMA node ID
• Hyperthread sibling CPU ID
• Frequency and power state

Maximum CPUs

FreeWorld supports up to 256 CPUs (MAX_CPUS = 256). This can be increased if needed.

CPU Topology

The system tracks CPU topology including:

• Physical package ID
• Core ID within package
• Thread ID within core
• SMT (hyperthread) ID

Status