3. 6. 1
Linux clone(), . fork(), .
, , . , , , , . , clone() (pid), .
( clone() ', ).
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Linux
Linux clone(). Linux , .
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POSIX 1996 , POSIX.
Linux
, Linux ᒺ, . , (pid). ³ , :
;
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3. 6. 2
, POSIX pthread_create() :
#include<pthread.h>
int pthread_create(pthread_t *th, pthread_attr *attr,
void *(*thread_fun)(void *).void *arg);
|
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:
th pthread_t, ; (thread handle).
Attr ( , );
thread_fun ,
void *mythread_fun(void *value)
{
//
}
arg , ( value).
POSIX:
#include<pthread.h>
//
void *thread_fun(void *num)
{
printf( %d\n,(int)num);
}
//
pthread_t th;
//
pthread_create(&th, NULL,thread_fun,(void *)++thread_num);
//
, . , main() , : , main(), .
POSIX
thread_fun() pthread_exit():
#include<pthread.h>
void pthread_exit(void *retval);
retval . :
void *turead_fun(void *num)
{
printf( %d\n,(int)num);
pthread_exit(0);
}
:
return main() , ;
pthread_exit() main() , , .
pthread_exit() , , .
pthread_join(). :
int pthread_join(pthread_t th,,void **status);
, , , , th, . status , , ( pthread_exit()). pthread_join(), .
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(long-term scheduling), c (medium-term scheduling) (short-term schediling).
4. 2. 1
, . , . , , . (, ) , ; . , . 㳿 , , , , .
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4. 2. 2
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, .
tn+1=aTn+(1-a)tn, 0 < a < 1, t0=T0,
tn+1 ;
tn ;
Tn .
a=0,5, .
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4. 4
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4. 5 Linux
Linux ( 2.4 ) ,
2.6.
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: FIFO, , .
4. 5. 1
, , :
;
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4. 5. 2
. (epochs). , . . , . . - , . , . .
, , . nice() setpriority(). - .
: , , , , , , . - - .
:
policy , (, FIFO );
nice , ( nice , );
counter , . counter .
, ( scedule()).
, . , .
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, , , . . , . , , .
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for each_task(p)
p.counter=(p.counter/2)+p.nice;
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0 , . . , , .
³ 0 1000 , . , . :
c=p.counter+p.nice;
p .
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4. 5. 4
Linux, ( nice) .
setpriority():
#include<sys/resource.h>
int setpriority(int which, int who,int priority);
, which PRIO_PROCESS PRIO_USER, , who . ( , who ), .
priority . 20 20, . 0. priority .
getpriority():
Int getpriority(int which, int who);
, which who , setpriority().
:
//
setpriority(PRIO_PROCESS,0,10);
//
printf( : %d\n,getpriority(PRIO_PROCESS,0));
nice():
#include<unistd.h>
int nice(int inc); // inc.
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5. 1 䳿
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, , , , .
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total_amount=total_amount+new_amount;
: , , , total_amount ?
:
total_amount ;
new_amount .
, . 100 . 1000, 100. , . ( 1).
1. total_amount, 100.
2. total_amount, 100.
3. 1 total_amount 1000, 1100 .
4. 2 total_amount 100, 200 , , .
.
( 2).
1. total_amount, 1000 1100 .
2. total_amount, 1100, 100 1200 .
.
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.
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//
total_amount=total_amount+new_amount;
//
, , , , , ( , ). 2, .
, .
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: , ( ).
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. , , , , , .
(locks). , . : (, acquire_lock()) (, release_lock()). , , , , . ϳ .
acquire_lock(lock);
//
release_lock(lock);
, (mutex, mutual exclusion).
. , . :
int lock=0;
void aquire_lock(int lock)
{
// (lock==0), ( lock=1)
//
// ,
while(lock!=0); //(1)
lock=1; //(2)
}
void release_lock(int lock)
{
//
lock=0;
}
, (1) (2) . , 0, .
5. 3
.
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:
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(down): , , , , (, ). wait. :
void down(semaphore_t sem)
{
if (sem>0)
sem--;
else sleep();
}
(up): ; , ,
