kyu ho park sept. 22, 2015 1 lecture 4 proc file system(procfs) (project 2 included) sept.19,4pm

Kyu Ho ParkSept. 22, 2015

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Lecture 4proc file system(procfs)

(Project 2 included)

Sept.19,4pm

Computer Engineering Research Labora-tory

Why do we need the procfs? To access the various information of the

Linux kernel easily, procfs has been pro-vided(firstly by Tom J. Killan, 1984 for UNIX on VAX machine).

Why we do not use the conventional file system using open, close, read, write sys-tem calls ?

It is always available and is accessible to all users, of course,with appropriate per-missions only.

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ls /proc

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/proc/cd 1

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cat cpuinfo

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meminfo

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Size of file at /proc directory

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Cat /proc/cpuinfo The contents of files under /proc directory

are created dynamically when you give commands such as

‘cat /proc/meminfo’.

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proc file system(procfs) functions

proc_mkdir( ); //make a directory under /proc. create_proc_entry( ); //make a file under /proc. create_proc_read_entry( ); //make a readonly file. remove_proc_entry( ); //remove dirs or files.

--procfs uses [struct proc_dir_entry] defined as follows; struct proc_dir_entry{

.....struct inode_operations *proc_iops;struct file_operations *proc_fops;..struct proc_dir_entry *next, *parent, *subdir;

void *data;read_proc_t *read_proc;write_proc_t *write_proc;atomic_t count;

int deleted;//in case of delete, this flag should be 0, if in use this flag is 1.

};

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//mostly used


Making a directory under /proc

struct proc_dir_entry *proc_mkdir(const char *name, struct proc_dir_entry *parent);

// name: the directory name to create,//parent: the parent of the directory to create.

parent

struct proc_dir_entry *son;struct proc_dir_entry *grand_son;son=proc_mkdir(“son”,NULL);grand_son=proc_mkdir(“grand_son”, son);

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son

grand_son

Ex:


File creation under /proc struct proc_dir_entry *create_proc_entry(const char *name,

mode_t mode,struct proc_dir_entry *parent);

//name: the RW file name to create. mode:file permission. To create read_only file, struct proc_dir_entry *create_proc_read_entry(const char *name,mode_t mode,struct proc_dir_entry *parent);

Ex:[create a ‘test’ file at /proc/test]struct proc_dir_entry *test_proc;test_proc=create_proc_entry(“test”, 0, NULL);

// if mode is set to 0, the default permission is 0444.

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Delete proc_files and direc-tories

void remove_proc_entry(const char *name, struct proc_dir_entry *parent);

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remove_proc_entry(“test”,NULL);remove_proc_entry(“grand_son”, son);remove_proc_entry(“son”,NULL);

test


read static int my_read(char *page, char **start, off_t off, int

count, int *eof, void *data) {

……//program codes*eof =1 ; when this function is called only one time.return len; //len: length of data read.

}-The memory space used in procfs is a page whose size is typ-ically 4KBytes. The location to save the data.-eof : end-of-file, if eof =1, no read anymore. -start: it is used rarely.-off: current location of the file.-data: not used in read.

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write static int my_write(struct file *file, const char *buffer, un-

signed long count, void *data) { char *proc_data;

proc_data=(char *)data;copy_from_user(kernel_data, buffer, count);

…return count; }

-buffer: user space data,-count: written data size,-*data: kernel address to store the data of buffer.

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for_each_process( ) at <linux/sched.h>

#include<linux/kernel.h>#include <linux/proc_fs.h>#include<linux/sched.h>#include<linux/module.h>

int read_process(char *buf, char **start, off_t off-set,int count,int *eof,void *data ){int len=0;struct task_struct *task_list;

for_each_process(task_list) {

len += sprintf(buf+len, "\n %s %d\n",task_list->comm,task_list->pid);

} return len;}

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void create_new_proc_entry(){create_proc_read_entry("proc_list",0,NULL,read_process,NULL);

}

int ps_init (void) { int ret; create_new_proc_entry(); return 0;}

void ps_exit(void) { remove_proc_entry("proc_list",NULL);}module_init(ps_init);module_exit(ps_exit);

MODULE_LICENSE("GPL");


cat /proc/proc_list

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proc_create( ) using seq_file

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proc_create() or create_proc_entry()

#include <linux/version.h>If (LINUX_VERSION_CODE )< VERSION(3,11,0)&&defined(CONFIG_PROC_FS)

create_proc_entry();else

proc_create( );

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2015. 09. 24.

Project 2.“Linux Fundamental”

procfs

By Dong Jae Shin


Introduction to Projects Project 1: Setting up Environment for Project Project 2: Linux Fundamental(procfs) Project 3: System Call and Synchronization Project 4: File System Project 5: Device Driver for Embedded H/W

Especially, including “BeagleBoard Development”

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Contents Follow-on Tasks

1. Linux System Administration 2. File System & Software Management 3. Build your own Linux Kernel

Project Tasks Write a System Monitoring Tools

1. Analyse the given skeleton program (10%) 2. Traverse Process tasklist (20%) 3. per Process Memory Usage (20%) 4. per Process I/O Usage (20%) 5. Process CPU Utilization (20% point Bonus)

Report (30%)------------------------------------------------------ Max. 100%


(1)Kernel Debugging Print Kernel-level Message

printk Kernel version of printf usage) printk(“%s %d %lu”, str, i, j );

Kernel Log Message tail -f /var/log/kern.log

See also (optional) for advanced debugging http://lwn.net/images/pdf/LDD3/ch04.pdf

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procfs

http://lwn.net/images/pdf/LDD3/ch04.pdf

http://lwn.net/images/pdf/LDD3/ch04.pdf


(2)/proc File System /proc

a special file system which displays the present of the system

pseudo and virtual file system which resides in the RAM

provides a method of communication between kernel space and user space

Various information provided by proc https://

www.kernel.org/doc/Documentation/filesystems/proc.txt

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procfs

https://www.kernel.org/doc/Documentation/filesystems/proc.txt




(3)/proc File System CPU Information

cat /proc/cpuinfo

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Main Memory Infor-mation cat /proc/meminfo

Kernel Debugging


(4)Create a proc entry Download Skeleton Files

# wget http://core.kaist.ac.kr/~EE516/Projects/Project2/Makefile

# wget http://core.kaist.ac.kr/~EE516/Projects/Project2/proc_sample.c

Compile # make

Useful ref) http://linux.die.net/lkmpg/c708.html

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procfs

http://core.kaist.ac.kr/~EE516/Projects/Project2/Makefile

http://core.kaist.ac.kr/~EE516/Projects/Project2/Makefile

http://core.kaist.ac.kr/~EE516/Projects/Project2/proc_sample.c

http://core.kaist.ac.kr/~EE516/Projects/Project2/proc_sample.c

http://linux.die.net/lkmpg/c708.html

http://linux.die.net/lkmpg/c708.html


(5)Test proc entry Kernel Log

# tail -f /var/log/kern.log Insert Module

insmod proc_sample.ko Write Proc File

# echo blahblah > /proc/proc_sample Read Proc File

# cat /proc/proc_sample Remove Module

# rmmod proc_sample

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procfs


Project Tasks Make a System Monitoring Tools

System monitoring is an important job especially on the embedded system

Low computing power, Less memory, Limited resources Monitoring tools

top, ps, netstat, gnome-system-monitor

Tasks 1.Analyze the given skeleton procfs program. (10%) 2. Traverse Process tasklist (30%) 3. per Process Memory Usage (30%) 4. per Process I/O Usage (30%) 5. Process CPU Utilization (10% point Bonus Task)

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Project Tasks


Task 1 Analyze the given skeleton of promon.c. Find the functions that you do not know

and explain the operations of those func-tions referring to references and Google.

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Task2. Traverse Task List Every Linux Tasks are managed by doubly linked list

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Print every task’s PID and Process Name in your proc file system Textbook Chapter 3. Understanding the Linux

Kernel, 3rd

Project Tasks


task_struct task_struct (=Process Descriptor)

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KERNEL/include/linux/sched.h

Useful materials : Textbook Chapter 3. of ULK

free e-book version : http://gauss.ececs.uc.edu/Courses/c4022/code/memory/understanding.pdf

Project Tasks

http://gauss.ececs.uc.edu/Courses/c4022/code/memory/understanding.pdf





task_struct

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………


Task3. Memory Usage Memory Mapping

RSS : Resident Set Size

VIRT : Virtual Memory Size

Print every task’s VIRT and RSS Memory Size

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VIRT RSS

RSSVIRT

Project Tasks


Task4. Process I/O Stat I/O Stat is stored in struct task_io_accounting

include/linux/task_io_accounting.h

Hint)

# cat /proc/PID/io rchar : read bytes by process wchar : written bytes by process syscr : # of read system calls syscw : # of write system calls read_bytes : read bytes from disk write_bytes : written bytes to disk

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write_bytes

read_bytes

Disk Cache in DRAM

Process

wcharrchar

Project Tasks


Task5. CPU Utilization “top” command

shows the CPU utilization per process

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Challenging Task (Bonus Point 10%) Kernel manages CPU ticks consumed by each

process in struct task_cputime

5. Project Tasks


Example of Output

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5. Project Tasks


Check your results Check the correctness of your results Task 2.

# ps -ef Task 3.

# top -b -n 1 Task 4.

Browser is a good test case (# firefox) Get pid

ps -ef |grep firefox # cat /proc/PID/io

Task 5. # top

Project Tasks


Submission Contents

Source Code Report

Project Tasks1~5 Key point of your Source Code Final Screenshots Page Limit : about 5 pages for Project Tasks1~5. (except fig-

ures)

Submission Due Date : Oct. 8, PM 23:59 Delay Penalty

10%/day (AM 00:00) E-mail : [email protected] [EE516 Project2] student_number.zip

(various compression format is allowed)

mailto:[email protected]

kyu ho park sept. 22, 2015 1 lecture 4 proc file system(procfs) (project 2 included) sept.19,4pm

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