Accessing a semaphore - assuming there is no deadlock - it is a direct memory access operation, adding a whole page or multiples to process memory has overhead. It can involve an expensive call: brk(), if no memory is already there.
It depends on what
says in total, rounded up to a minimum of the PAGE_SIZE (mutiple) boundary (stack frame boundary usually), which can leave extra multiple pages of memory. Look at what is show to be allocated to heap. As a start. You can call sbrk(0) to find the end of process memory.
shmget allocates from heap in most implementations: /proc/sys/kernel/sh* proc directories have shared memory information. kernel settings control shared memory operations.
try this:
That will display cum time spent + # calls for each of the function calls. You can see if/where there is a problem. If there is one with semaphores then semget will be your most likely problem - allocating pages of memory.
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)
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)
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)
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)
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)
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 OPENSOLARIS
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)