Pintos code hacking by sg20180546

1. Thread (clear at 9/2)

1) Alarm Clock

1 tick = 10 ms = 0.01s
if timer_sleep, insert into struct list sleep_list
Each timer interrupt, test all elem in sleep list and get thread wake up.

2) Scheduler

When a thread is added to the ready list that has a higher priority than the currently running thread, the current thread should immediately yield the processor to the new thread.
nested priority donation

3) Advanced Scheduler : Multi Level Feedback Queue Scheduler (mlfqs)

integer : priority, ready_threads nice
fixed point : recent_cpu, load_avg
priority = PRI_MAX - (recent_cpu / 4) - (nice * 2)
recent_cpu = (2*load_avg)/(2*load_avg + 1) * recent_cpu + nice
load_avg = (59/60) * load_avg + (1/60) * ready_threads
Each Timer interrupt (10 ms, 1 tick)
Every 40 ms (4 tick)
Every 1 second(1 tick * TIME_FREQ)
parameter dependecies

- flow chart

- disable thread_set_priority(int new_priority) - disable priority donation - little issue in mlfqs-load-avg

2. User Program (clear at 10/2)

1) process_wait

process wait list in child, which is running
process wait elem in parent, which is waiting for the process exit
parent blocked and inserted to wait list of running ps
if running process exit, update exit status for waiting processes and unblock those.

2) argument passing by stack (executing)

use intr_frame
*esp == system call number
*(esp+i)== system call argument

3) system call handler

Handling system call

linux interrupt vector table (IVT)

fail at novm-oom

3. VM (clear at 11/22)

pintos page pool(palloc.c) layout

1) Demand Paging

load_segment : map vm_entry -> ELF file offset , not load file on phys
Overview of DISK ELF transformed to MEMORY
page_fault : load file by certain file offset at vm entry
Swapping by Clock Algorithm
- IA32 3.7.6 : ACCESS,PRESENT / set by HARDWARE, clear by SOFTWARE(OS)
- When vaddr Access : handle page fault and load(set PTE PRESENT by HARDWARE), insert lru_list -> Hardware set PTE access bit(reference bit) to 1
- Replacement : traverse lru_list(circular, struct page) and check access bit
  -> if access bit==1 : set access bit 0; next;
  -> if access bit==0 : evict page(pagedir_clear_page); load file to kaddr; map page(install_page);
  -> if dirty bit ==1 or vme_types==VM_ANON : need to be SWAP OUT, vme types=VM_ANON

2) Stack Growing

Check vaddr is valid stack growing area (pintos ULIMIT: 1MB , pusha : 8 byte low than cur sp)
new vm entry about new stack area, VM_ANON
SWAP OUT to SWAP DISK

3) Swap Partition

pintos-mkdisk swap.dsk --swap-size=4

IA32 3.7.6 : DIRTY set by HARDWARE, clear by SOFTWARE
sizeof SECTOR = 512 bytes, sizeof PAGE = 4092 bytes
If swap in/out , write/read to 8(PGSIZE/BLOCK_SECTOR_SIZE) sector
Before filesys project, Overview of pintos SATA disk layout
managing (free) swap partition by bitmap

4) Memory Mapping files

Files to memory
memory needs to be sync to file when unmap, process exited.

fail at page-merge-mm

5. Filesys (progressing)

command

set gcc older version
sudo update-alternatives --config gcc
pintos gdb
shell1 )
src/userprog/build $ pintos --gdb -v -k -T 60 --qemu --filesys-size=2 -p tests/userprog/args-multiple -a args-multiple -- -q -f run 'args-multiple some arguments for you!'

shell @)
src/userprog/build $ gdb kernel.o
(gdb) target remote localhost:1234
(gdb) continue

threads
pintos run alarm-multiple
gs201@gs201-14Z90N-VR5DK:~/Desktop/pintos/src/threads/build$ make tests/threads/alarm-multiple.result.
gs201@gs201-14Z90N-VR5DK:~/Desktop/pintos/src/threads/build$ make check
userprog
pintos-mkdisk filesys.dsk --filesys-size=2
pintos -f -q
pintos -p ../../examples/echo -a echo -- -q
pintos -q run 'echo x'
pintos --filesys-size=2 –p ../../examples/echo –a echo -- -f –q run ‘echo x’
vm
src/userprog/Make.vars
KERNEL_SUBDIRS = threads devices lib lib/kernel userprog filesys vm
if there is new c file to compile, Makefile.build
vm_SRC = vm/page.c

jesscel/pintos-1