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+# Dev log 
+## **1. Process Management:** 
+The core architecture has been upgraded from a simple single queue to a Per-CPU scheduler, supporting multi-core concurrency. 
+
+* Process lifecycle: A complete process state machine has been implemented, including UNUSED, RUNNABLE, RUNNING, SLEEPING, and ZOMBIE states. 
+
+* Core operations: 
+    * fork(): process cloning, supporting COW (copy-on-write) isolation of memory space between parent and child processes. 
+    * exit(): process termination and resource cleanup. 
+    * wait(): parent process waits for child process to exit. 
+    * sleep()/wakeup(): channel-based sleep and wakeup mechanism. 
+
+* Scheduling algorithm: 
+    * O(1) priority scheduling has been implemented (supporting 4 priority queues). 
+
+    * Per-CPU RunQueue: each CPU has its own independent run queue. 
+
+    * Supports Work Stealing: idle CPUs can fetch tasks from other CPUs’ queues. 
+
+## **2. Memory Management:** 
+A complete virtual and physical memory management system has been implemented. 
+
+* Physical Memory (PMM): Implements the Buddy System, supporting memory allocation and deallocation in $2^n$ pages. 
+
+* Virtual Memory (VM): Based on RISC-V Sv39 paging mode. Provides secure data copying from user space to kernel space (copyin). 
+
+* COW (Copy-On-Write): During fork, only page table entries are copied and pages are set to read-only; writes trigger page faults for physical copy, greatly improving process creation efficiency. 
+
+* Kernel heap: Implements a Slab Allocator, providing efficient allocation of small objects (such as struct Proc). 
+
+## **3. Synchronization:**
+
+* Spinlock: Used to protect very short critical sections (e.g., scheduler lock, PMM lock), supports disabling interrupts to prevent deadlocks. 
+
+* Mutex (sleeping lock): Used for long critical sections (e.g., file I/O), allowing sleep while holding the lock. 
+
+* Lock Handoff: Implements a complex lock handoff mechanism in the scheduler to ensure atomicity of context switches. 
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