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 302237980 by migurus on Thursday 18th of September 2008 09:22:22 PM
Old 09-18-2008
I simplified my program to the very basic minimum, it gets ipc key, gets semaphore id and reads values of semaphores and then it outputs on line (time and semaphore values). That is all it does.

Then I run it in following manner:
$ while : ; do tstshow; done > x.txt
and I hit interrupt key after waiting for some time.

sample of the x.txt file content:
1221785538 [1,99]
1221785538 [1,99]
1221785538 [1,99]


Then to see how many times system was able to run it I do:
$ cut -c-12 x.txt | uniq -c

sample of the output:
616 1221785538
615 1221785539
612 1221785540

That tels me the system is capable of running this simple process just roughly 600 times per second.

Just to be consistent I would repeat results here:
PIII under Linux - 900 times/sec
Xeon 3.2 Linux - 600 times/sec
Xeon 3.2 SCO - 1800 times/sec
Systems are idle at the time of test.
How would you explain the results I got? I am trying to find a bottleneck on the modern h/w running Linux.

Please see my new simplified code below:

Code:
 
#include <stdio.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <time.h>
#define NSEMS   2
main(int argc, char *argv[])
{
  int           sid;
  ushort        vals[NSEMS] = {0, 0};
        if((sid = semget(get_ipc_key(), NSEMS, 0)) == -1)
        {
                errexit("Can Not Get Semaphore ID");
        }
        if(semctl(sid, NSEMS, GETALL, vals) == -1)
        {
                errexit("Can Not Get Semaphore Values");
        }
        printf("%12li [%i,%i]\n", time(NULL), vals[0], vals[1]);
        exit(0);
}

 

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 SUNOS

semaphore

semaphore.h(3HEAD)						      Headers							semaphore.h(3HEAD)

NAME

       semaphore.h, semaphore - semaphores

SYNOPSIS

       #include <semaphore.h>

DESCRIPTION

       The  <semaphore.h>  header  defines  the sem_t type, used in performing semaphore operations. The semaphore can be implemented using a file
       descriptor, in which case applications are able to open up at least a total of {OPEN_MAX} files and semaphores. The  symbol  SEM_FAILED	is
       defined (see sem_open(3RT)).

       Inclusion  of  the <semaphore.h> header can make visible symbols defined in the headers <fcntl.h> and <sys/types.h>. See fcntl.h(3HEAD) and
       types.h(3HEAD).

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       fcntl.h(3HEAD), types.h(3HEAD),	sem_destroy(3RT),  sem_getvalue(3RT),  sem_init(3RT),  sem_open(3RT),  sem_post(3RT),  sem_timedwait(3RT),
       sem_unlink(3RT), sem_wait(3RT), attributes(5), standards(5)

SunOS 5.10							    10 Sep 2004 						semaphore.h(3HEAD)
All times are GMT -4. The time now is 05:38 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy