treesls/docs/TreeSLS.md

Implementation of TreeSLS

We implemented TreeSLS based on ChCore, which is an educational multicore microkernel that supports POSIX APIs through musl-libc.

TreeSLS's modification includes:

• checkpoint/restore module (kernel/ckpt)
• memory allocator module (kernel/mm)
• ipi module (kernel/ipi)
• several new syscalls (kernel/syscall)
• user applications (listed in user/sample-apps/apps/treesls)

Checkpoint/Restore

TreeSLS adds a checkpoint/restore module (kernel/ckpt). Whole-system checkpoint/restore can be taken through sys_whole_ckpt (kernel/ckpt/ckpt.c) and sys_whole_restore (kernel/ckpt/restore.c).

Hybrid page checkpointing is done through process_sub_active_list(), which is called in parallel to the main process of checkpointing.

Memory Allocator

TreeSLS modifies the memory allocator (kernel/mm) by adding a lightweight journal when malloc and free pages from the buddy system. The journal is taken through prepare_latest_log() in every malloc/free function.

Other Modules (IPI, syscall, etc.)

TreeSLS also modified some other modules (IPI, syscall, etc.) to enable checkpointing.

1. IPI: add sys_ipi_stop_all and sys_ipi_start_all.
2. syscall: export sys_whole_ckpt, sys_whole_restore, and several supporting syscalls.