CS 140. Lab 1 - Threads

Transcription

1 CS 140 Lab 1 - Threads

2 setup lab 1 git general

3 setup lab 1 git general

4 Getting started with pintos

5 Get the Source set your path set path = ( /usr/class/cs140/`uname -m`/bin $path ).cshrc file pintos already working on cluster machines corn, cardinal, myth, get pintos src code git clone or zcat /usr/class/cs140/pintos/pintos.tar.gz tar x threads userprog vm filesys devices lib lib/kernel lib/user tests examples misc utils

6 Building Pintos cd threads make will create a build directory Makefile - describes how to build the kernel and add source files kernel.o - object file for kernel; contains debug info kernel.bin - memory image of the kernel; bascially kernel.o without debug info loader.bin - assembly that reads the kernel from disk into memory and starts it up

7 Running Pintos run individual tests pintos run alarm-multiple run a test run all tests make check which test to run

8 setup lab 1 git general

9 Lab 1 : threads two dirs : threads and devices devices/timer.c threads/fixed-point.h threads/synch.c threads/thread.c threads/thread.h read existing code Pintos already implements thread creation and thread completion, a simple scheduler to switch between threads, and synchronization primitives (semaphores, locks, condition variables, and optimization barriers).

10 Alarm clock timer_sleep(num_ticks) current version busy_waits what you need to do: put thread to sleep for num_ticks it gets put in ready queue TIMER_FREQ ticks per sec specified in devices/timer.h don t change this tests will fail timer_msleep(), timer_usleep(), timer_nsleep() call timer_sleep() and do not need to be modified

11 Priority Scheduling implement scheduler current scheduler just does round robin RULES thread with highest priority is always running unless it is blocked highest priority waiting thread should be awoken first

12 Priority Scheduling PRI_MIN -> 0 PRI_MAX -> 63 PRI_DEFAULT -> 31 can find these in threads/thread.h

13 Priority Scheduling Scenario 1 ready running blocked C 4 A 3 D 1 B F 10 G H 0

14 Priority Scheduling Scenario 1 tries to acquire lock ready running blocked C 4 A 3 D 1 B F 10 G H 0

15 Priority Scheduling Scenario 1 tries to acquire lock ready running blocked C 4 A 3 D 1 B F 10 G H 0

16 Priority Scheduling Scenario 1 tries to acquire lock ready running blocked C 4 A 3 D 1 B F 10 G H 0

17 Priority Scheduling Scenario 1 tries to acquire lock ready running blocked C 4 A 3 D 1 B CF 10 4 G F 10 H 0

18 Priority Scheduling Scenario ready running blocked C 4 A 3 D 1 B F 10 G H 0

19 Priority Scheduling Scenario unlocks lock G and H were waiting on ready running blocked C 4 A 3 D 1 B F 10 G H 0

20 Priority Scheduling Scenario unlocks lock G and H were waiting on ready running blocked C 4 A 3 D 1 B F 10 G H 0

21 Priority Scheduling Scenario unlocks lock G and H were waiting on ready running blocked C 4 A 3 D 1 B F 10 HF 10 0 G H 0

22 Priority Scheduling Scenario 3: Priority Inversion ready running blocked A 1 C 3 B

23 Priority Scheduling Scenario 3: Priority Inversion ready running blocked A 1 B C 3 tries to acquire lock that A holds

24 Priority Scheduling Scenario 3: Priority Inversion ready running blocked A 1 CB 3 C 3 B What can we do?

25 DONATE

26 Priority Scheduling Donation ready running blocked A 1 B C 3

27 Priority Scheduling Donation ready running blocked A 3 B A 3 1 C 3 B

28 Priority Scheduling Donation ready running blocked A CA 3 1 C 3 B

29 Priority Scheduling Donation multiple donation a thread is holding two locks that higher priority threads are waiting on respectively nested donation a high priority thread is waiting on a lower priority thread to release a lock which in turn is waiting on an even lower priority thread to release a lock A 1 B C 3 both waiting on the same lock or both waiting on a different lock A 1 B C 3 C is waiting for B to release his lock. Donates to B B runs and then gets blocked on a lock that A holds B donates to A

30 Priority Scheduler void thread_set_priority (int new_priority) Sets the current thread's priority to new_priority. If the current thread no longer has the highest priority, yields. int thread_get_priority (void) Returns the current thread's priority. In the presence of priority donation, returns the higher (donated) priority.

31 Advanced Scheduler no priority donation -mlfqs kernel option. You must write your code to allow us to choose a scheduling algorithm policy at Pintos startup time. parse_options() The priority argument to thread_create() should be ignored, as well as any calls to thread_set_priority() thread_get_priority() should return the thread's current priority as set by the scheduler.

32 Advanced Scheduler 4.4BSD Scheduler multilevel feedback queue maintains several queues of ready-to-run threads each queue holds threads with a different priority pick from highest priority queue if many threads are in highest priority queue they run in round robin order update data after a certain number of ticks updates need to happen before any ordinary kernel thread has a chance to run, so that there is no chance that a kernel thread could see a newly increased timer_ticks() value but old scheduler data values

33 Advanced Scheduler 4.4BSD Scheduler - Niceness Thread priority is dynamically determined by the scheduler using a formula Niceness 0 -> does not affect thread priority >0 -> decreases the priority of a thread and causes it to give up some CPU time it would otherwise receive ( max of 0) <0 -> tends to take away CPU time from other threads ( min of -0) The initial thread starts with a nice value of zero Other threads start with a nice value inherited from their parent thread.

34 Advanced Scheduler 4.4BSD Scheduler - Niceness int thread_get_nice (void) Returns the current thread's nice value. void thread_set_nice (int new_nice) Sets the current thread's nice value to new_nice and recalculates the thread's priority based on the new value. If the running thread no longer has the highest priority, yields.

35 Advanced Scheduler 4.4BSD Scheduler - Calculate Priority priorities range from 0 to 63 calculated every 4rth tick for every thread where recent_cpu has changed recalculated priority

36 Advanced Scheduler int thread_get_recent_cpu (void) Returns 100 times the current thread's recent_cpu value, rounded to the nearest integer. int thread_get_load_avg (void) Returns 100 times the current system load average, rounded to the nearest integer. pay attention to when you should update these values

37 Advanced Scheduler Fixed-Point Real Arithmetic priority, nice, and ready_threads are integers, but recent_cpu and load_avg are real numbers Pintos does not support floating-point arithmetic in the kernel, because it would complicate and slow the kernel. So you get to do it. YAY! detailed explanation here: html#sec137a

38 setup lab 1 git general

39 Git Setup $ git init $ git add. //for each group member $ fs sa. <sunet_id> all $ git clone <full path> //i.e. /afs/ir.stanford.edu/users/d/i/diakite/140

40 Git Basic Commands git add git push git log git commit git status git pull git stash

41 Git slightly more advanced git diff ( --cached) git branch git checkout git reset git merge git rebase -i gitk git show git cherry-pick git commit --ammend

42 setup lab 1 git general

43 Things to note are interrupts off if yes there is no concurrency are you updating things at the right time smart design decisions write clean code

44 General tips start early meet as a group and integrate often use source control (git) think about design before you start coding multithreaded so run multiple times

45 General tips jitter pintus -j seed introduce interrupts at regular intervals with seed Do not rush your design doc 50 % of credit look at the template get acquainted with tools early; i.e. backtrace and gdb

46 Due : Friday, January 4

47 That s It

48 Fun Stuff can modify your tests/tests.pm to get colors for your use Term::ANSIColor qw(:constants); $Term::ANSIColor::AUTORESET = 1; if ($verdict eq 'PASS') { print STDOUT GREEN "pass $test\n"; } else { print STDOUT RED "FAIL $test\n"; }