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 SUNOS
semaphore.h
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)