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 302243827 by migurus on Monday 6th of October 2008 03:54:40 PM
Old 10-06-2008
Otheus, I never dealt with reporting on bugzilla, it seems ti me I don't quite qualify and I'm afraid I will post something not pertinent, so if you would agree to do it yourself, here are the results from 2nd version of your 'gettimeofday-based' code, which I re-run 4 times as to get average:

SCO
$ tmx2
575108.94 semop/s (5000000/8694005)
$ tmx2
575215.00 semop/s (5000000/8692402)
$ tmx2
575183.63 semop/s (5000000/8692876)
$ tmx2
559832.49 semop/s (5000000/8931243)

Linux:
$ ./tmx2
129363.77 semop/s (5000000/38650699)
$ ./tmx2
129428.22 semop/s (5000000/38631452)
$ ./tmx2
129601.55 semop/s (5000000/38579786)
$ ./tmx2
129511.76 semop/s (5000000/38606534)


As you see, no difference from the former tests.

Just for my clarification: somehow people who participated in this discussion on unix.com formu as well as on kerneltrap and other places were very concerned with 2 things, that in my perspective are irrelevant to the subject of this thread: time measurement accuracy and involvement of running multiple processes/shells etc that would muddy the results. I would wholeheartedly agree to that IF SCO vs Linux results were comparable. But this is not the case here. SCO is three times faster, no matter we used my method or gettimeofday very accurate method. With all the overhead being roughly similar, I would think we were kind of beating around the bush when we were trying to achieve have accuracy in measurement (which does not hurt, of cource!), but it made the thread bloated.

Again, thanks to Otheus for your suggestions, at this point I the kernel code you pinpoint shows that multi-cpu capability adds a layer of complexity and it does not help the speed. Your and strcmp's (kerneltrap forum) recomendations to upgrade Linux kernel are well taken.
migurus
 

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 CENTOS

sdl_semwaittimeout

SDL_SemWaitTimeout(3)						 SDL API Reference					     SDL_SemWaitTimeout(3)

NAME

       SDL_SemWaitTimeout - Lock a semaphore, but only wait up to a specified maximum time.

SYNOPSIS

       #include "SDL.h" #include "SDL_thread.h"

       int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout);

DESCRIPTION

       SDL_SemWaitTimeout()  is a varient of SDL_SemWait with a maximum timeout value. If the value of the semaphore pointed to by sem is positive
       (greater than zero) it will atomically decrement the semaphore value and return 0, otherwise it will wait up to timeout milliseconds trying
       to  lock the semaphore. This function is to be avoided if possible since on some platforms it is implemented by polling the semaphore every
       millisecond in a busy loop.

       After SDL_SemWaitTimeout() is successful, the semaphore can be released and its count  atomically  incremented  by  a  successful  call	to
       SDL_SemPost.

RETURN VALUE

       Returns	0  if  the  semaphore was successfully locked or either SDL_MUTEX_TIMEOUT or -1 if the timeout period was exceeded or there was an
       error, respectivly.

       If the semaphore was not successfully locked, the semaphore will be unchanged.

EXAMPLES

       res = SDL_SemWaitTimeout(my_sem, WAIT_TIMEOUT_MILLISEC);

       if (res == SDL_MUTEX_TIMEOUT) {
	       return TRY_AGAIN;
       }
       if (res == -1) {
	       return WAIT_ERROR;
       }

       ...

       SDL_SemPost(my_sem);

SEE ALSO

       SDL_CreateSemaphore, SDL_DestroySemaphore, SDL_SemWait, SDL_SemTryWait, SDL_SemPost, SDL_SemValue

SDL
							      Tue 11 Sep 2001, 23:00					     SDL_SemWaitTimeout(3)
All times are GMT -4. The time now is 10:47 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy