Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: semaphore access speed
Top Forums Programming semaphore access speed Post 302242065 by otheus on Wednesday 1st of October 2008 05:42:14 AM
Old 10-01-2008
Here is my code:
Code:
#include <stdio.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <time.h>
#define NSEMS   2

/* change this per CPU to run between 8 and 12 s*/
const static int maxloop = 10000000; 

main(int argc, char *argv[])
{
    time_t start,last,stop;
    long int i;
    int estimate = 100;
    int sid;
    key_t key;
    ushort vals[NSEMS] = { 0, 0 };

    key = ftok("/tmp",99);
    last=start=time(NULL);
    for (i = 0; i < 1000; ++i) {
        usleep(10);
        last=time(NULL);
        if (last > start) break;
    }
    start=last;
    last = 0;

    for (i = maxloop/8; i < maxloop; i++) {
      if ((sid = semget(key, NSEMS, IPC_CREAT | 0777)) == -1) {
          perror("Can Not Get Semaphore ID");
      }
      if (semctl(sid, NSEMS, GETALL, vals) == -1) {
          perror("Can Not Get Semaphore Values");
      }
    }

/* do the last 1/8th until the second changes.
    If your processor reaches the maxloop before that,
    change the maxloop or the divisor or the "estimate" */

    stop=time(NULL);
    for (i = maxloop - maxloop/8; i < maxloop; ++i) {
      if ( !(i % estimate) ) {
        last=time(NULL);
        if (last > stop) break;
        stop=last;
      }

      /* repeat semaphore opts */
      if ((sid = semget(key, NSEMS, IPC_CREAT | 0777)) == -1) {
          perror("Can Not Get Semaphore ID");
      }
      if (semctl(sid, NSEMS, GETALL, vals) == -1) {
          perror("Can Not Get Semaphore Values");
      }
    }
    stop=last;

    printf("%.2f semop/s (%i/%i) [%d]\n", (double)i/(stop-start), i, stop-start, estimate);
}

 

9 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

semaphore

hi, is there any command where we can monitor semaphores? (1 Reply)
Discussion started by: yls177
1 Replies

2. UNIX for Dummies Questions & Answers

Semaphore

Hi, I'm new to UNIX. I need to know what's a semaphore Do reply. Thanks VJ (3 Replies)
Discussion started by: vjsony
3 Replies

3. Filesystems, Disks and Memory

dmidecode, RAM speed = "Current Speed: Unknown"

Hello, I have a Supermicro server with a P4SCI mother board running Debian Sarge 3.1. This is the "dmidecode" output related to RAM info: RAM speed information is incomplete.. "Current Speed: Unknown", is there anyway/soft to get the speed of installed RAM modules? thanks!! Regards :)... (0 Replies)
Discussion started by: Santi
0 Replies

4. Shell Programming and Scripting

Semaphore

Hi, I am looking to use a semaphore for the first time in one of my scripts. I am just wondering if there are any simple examples or tutorials around? I am a beginner so the simpler the better :) Thanks -Jaken (2 Replies)
Discussion started by: Jaken
2 Replies

5. UNIX for Dummies Questions & Answers

semaphore

what is semaphore? can any body explain it in a more simple way than the manual ?? replies appreciated Regards raguram R (7 Replies)
Discussion started by: raguramtgr
7 Replies

6. Filesystems, Disks and Memory

data from blktrace: read speed V.S. write speed

I analysed disk performance with blktrace and get some data: read: 8,3 4 2141 2.882115217 3342 Q R 195732187 + 32 8,3 4 2142 2.882116411 3342 G R 195732187 + 32 8,3 4 2144 2.882117647 3342 I R 195732187 + 32 8,3 4 2145 ... (1 Reply)
Discussion started by: W.C.C
1 Replies

7. Shell Programming and Scripting

semaphore

Control two exclusively shared resources(semaphore). The two resources are two files. The producer will write even numbers to one file, and odd numbers to another one. The consumer respectively reads from each file until it gets 5 even numbers and 5 odd numbers. Can any one help me with the... (0 Replies)
Discussion started by: gokult
0 Replies

8. Programming

Semaphore

If I create a semaphore and then I fork a number of child processes then all the child process use that same semaphore. Since the process address spaces are different rfom each other then how all the child process are able to access the same semaphore? I understand that semaphore/mutex is at os... (0 Replies)
Discussion started by: rupeshkp728
0 Replies

9. UNIX for Beginners Questions & Answers

Semaphore

I was asked to add this piece of code to a c program which I will execute through the shell: for(long i = 0; i < NITER; i++) { sem_wait( &sema); count++; sem_post( &sema); } I didn't get it, which is the critical section ? if it's "count++" how would a thread wake up in order to enter it... (1 Reply)
Discussion started by: uniran
1 Replies

LEARN ABOUT POSIX

sem.h

<sys/sem.h>(P)						     POSIX Programmer's Manual						    <sys/sem.h>(P)

NAME

       sys/sem.h - XSI semaphore facility

SYNOPSIS

       #include <sys/sem.h>

DESCRIPTION

       The <sys/sem.h> header shall define the following constants and structures.

       Semaphore operation flags:

       SEM_UNDO
	      Set up adjust on exit entry.

       Command definitions for the semctl() function shall be provided as follows:

       GETNCNT
	      Get semncnt.

       GETPID Get sempid.

       GETVAL Get semval.

       GETALL Get all cases of semval.

       GETZCNT
	      Get semzcnt.

       SETVAL Set semval.

       SETALL Set all cases of semval.

       The semid_ds structure shall contain the following members:

	      struct ipc_perm  sem_perm  Operation permission structure.
	      unsigned short   sem_nsems Number of semaphores in set.
	      time_t	       sem_otime Last semop
	       () time.
	      time_t	       sem_ctime Last time changed by semctl
	       ().

       The pid_t, time_t, key_t, and size_t types shall be defined as described in <sys/types.h> .

       A semaphore shall be represented by an anonymous structure containing the following members:

	      unsigned short  semval   Semaphore value.
	      pid_t	      sempid   Process ID of last operation.
	      unsigned short  semncnt  Number of processes waiting for semval
				       to become greater than current value.
	      unsigned short  semzcnt  Number of processes waiting for semval
				       to become 0.

       The sembuf structure shall contain the following members:

	      unsigned short  sem_num	Semaphore number.
	      short	      sem_op	Semaphore operation.
	      short	      sem_flg	Operation flags.

       The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.

	      int   semctl(int, int, int, ...);
	      int   semget(key_t, int, int);
	      int   semop(int, struct sembuf *, size_t);

       In addition, all of the symbols from <sys/ipc.h> shall be defined when this header is included.

       The following sections are informative.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       <sys/ipc.h> , <sys/types.h> , semctl(), semget(), semop()

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
       Electrical  and	Electronics  Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE
       and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can  be  obtained
       online at http://www.opengroup.org/unix/online.html .

IEEE
/The Open Group						       2003							    <sys/sem.h>(P)
All times are GMT -4. The time now is 04:18 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy