I have 2 applications that send and receive messages through shared memory IPC. When I run the app ..it works but the number of messages per sec keeps changing drastically sometimes it is 400-500 per sec..then 800 then 1200 then 2000. is this normal with SHM IPC or could it be a code related issue.
View 9 RepliesI want to create a "Shared Memory" in linux, then create multiple "Shared Objects" that can access to a Table for example; And one of them can write something into the Table and the other can access and read it, so that these operations can be handled by programmer! I'm using Ubuntu 9.04 and I've set it's runlevel at 3 (I have commandline environment now!) I've searched the Internet so much, but couldn't find a good sample code for this! I have no experience about it and need your help to introduce me a sample code about it and advise me how to compile and use it with "GCC"?!
View 6 Replies View RelatedAny good tutorial on sharing dynamically allocated objects across shared libraries in the same process and between shared libaries and main(). In particular, I need to know what creation and destruction sequences are valid when libraries are being loaded and unloaded. For example, is it valid to allocate an object from inside a shared library procedure, and then delete that pointer from a different module, especially in the case where the allocating module has already been unloaded.
I imagine there might be all kinds of problems with this. Although my preliminary tests seem to work most of the time, I get crashes from time to time, but I'm not sure if they're caused by memory management or by threading issues. I've been restructuring my code to use a global context object to manage object creation and destruction from main(), but I'd like to find a clear exposition of the specific issues I'm dealing with before I go too much further.
I'm writing a producer-consumer program, where the producer and the consumer are different processes and they communicate using queued signals, and when I run it it comes out always 'segmentation fault'.
Here is my code:
(note: I tried using both 'shm_open()' and 'mmap()', and 'shmget()' and shmat()')
Code:
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
[code]....
So I'll try to be brief and to the point here: I've got a couple of C / C++ apps that communicate with one another via shared memory. These worked completely fine until.. well, about twenty minutes ago when I finished making some network card changes and suddenly, I've got a weird problem going on. At one point, Parent app waits for Child app to set a boolean indicating it's finished initialization. This worked fine the last time I ran this app up (a few days ago). But right now, the shared flag never seems to get triggered (I've added a printf("Waiting..."); in Parent app until the flag is set). All the code leading up to it being set in Child app seem to be running smoothly, so I tried spitting out the addresses of the shared memory locations. The addresses mapped by Parent app and Child app are different; this seemed odd, so I went back and wrote a simple miniature app that just opened a shared structure on my own box, and I get the same thing - different addresses - but the miniature apps work just fine.
Is it normal for a shared memory space to be mapped to two different addresses across two processes?
If so, does anyone have any idea what might be the issue at hand with my Parent / Child app scenario? The Child creates the shared memory, the Parent has a wait before it opens it, and if it doesn't exist should fail (opening with PROT_READ | PROT_WRITE)... it doesn't fail so it's evidently there.
All of this worked until literally just a few hours ago and I made some changes to my network cards, and I can't even imagine how that could have changed whether or not shared memory mapping worked...
I have what should be a relatively simple program (fadec.c) that maps a struct from an included header file (fadec.h) to a shared memory region, but Im struggling accessing members in the struct from the pointer returned by shmat. Ultimately, I want to access members in the shared memory structure with a globally declared version of the struct, shm__. Not only do I not know how to accomplish that, but I cant even seem to access members of the shared struct directly from the pointer itself (compiler complains about dereferencing pointer to incomplete type). Im at a loss and could use another set of eyes if you guys dont mind taking a gander:
Compile Errors:
tony-pc:/cygdrive/p/test> cc -o fadec fadec.c
fadec.c: In function 'main':
fadec.c:30: error: dereferencing pointer to incomplete type
fadec.c:31: error: dereferencing pointer to incomplete type
[Code]...
I have a program that creates and uses a shared memory segment. I am trying to find out how to detach and delete this shared memory segment when I hit crtl-C, and I still need the process to terminate.shmdt() and shmctl() have variables that are local to the main passed to them(shared and shmid)
Code:
//Prototype
void leave(int sig);
//part of code trying to use signal handling
if(signal(SIGINT, leave))
[Code]...
if i attach a shared memory to my process whch part of the address space it will add(like stack, heap, data, code...).
View 3 Replies View Relatedhow come shared memory is only using 4 gigs of ram?
Code:
localhost router # free -m
total used free shared buffers cached
Mem: 8001 858 7142 0 130 235
-/+ buffers/cache: 492 7508
[code]...
I am trying to troubleshoot an Apache/Mysql server that once every few days falls over due to memory starvation. I thought I had tuned my httpd.conf file with relativley small MaxClients and so on, but then noticed some unusual RES values in top while monitoring.
In short, `top -b -n1 -u apache` shows that I have 28 httpd processes. their VIRT is ~300MB for each process (I understand this is shared), and the RES ~50MB for each. I thought this wasn't shared. Is this true? I just noticed 2 of the processes jump to 1.2g. If RES represents non-shared memory then concievably 1.2g x 28 processes would be a problem on an 8GB server.
Does anyone know if there is a size limitation for shared-memory segments in RHEL AS 4?
View 1 Replies View RelatedI am new to C and linux. My code below does arbitary writes but I cant figure out where or how it does it.
I am calling the insertNode() function with seq = 'MISSISSPPI$' and alphabets = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ$'
Code:
Weird behaviour I should mention is that when I check for NULL pointer in node->child[index], the unassigned values are not null anymore, they point to arbitary memory.
I'm running a Debian based distro.
When I run ipcs this pops up:
This happens only while KDE3 is running. Regardless of the runlevel, if kdm is not started, this will not show.
By running ipcs -p the PID points to process
Is there anything wrong with that command?
When I boot into Linux i see some shared memory which is blocked, due to this I am unable to start my processes which needs some shared memory.I tried removing the shared memory using ipcrm -m but no use, the shared memory is not cleaned but its still in use.I tried removing the shared memory using root user also normal user but unable to remove the shared memory.
[pin01]$ ipcs -m
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
[code]...
I have to figure out how to pass data between a Fortran application and a C++ application. The memory has to be locked/unlocked to prevent data corruption. I know very little about Fortran. I have done mutex lock/unlock stuff in Linux apps, multi-threaded, using mutex locks before.
Digging around on the Web, I do not find any info on a Fortran app including linux headers, library calls such as those in ipc.h, shm.h and sem.h. What is an approach to this problem?
How do I write a script for my Linux that can show me total memory vs used memory and have it email me results if it's over 70 percent?
View 2 Replies View RelatedWhen the systen is running there is a program/utility/kernel-driver? kthreadd in system monitor all the following programs are a child process of kthreadd. Is kthreadd part of elevator=cfq and can kthreadd be influenced by params. kthreads uses no cpu time memory or shared memory so it must be in kernel. is there any documentation on this subject? System 11.3 on quad processor 8 gb mem nvidia-card and driver.
View 3 Replies View RelatedHow do I change the size of the available shared memory on Linux?evidently 4GB is not enough for what I am doing (I need to load a lot of data into shared memory - my machine got 8GB of RAM).
View 2 Replies View RelatedIs that possible that SHM shared memory is counted as cache memory on Linux with kernel 2.6.18?If find it really odd since this memory is not file backed, but I have a piece of code that loads data using shm_open+mmap, and it generates an amount of cache memory in /proc/meminfo that corresponds exactly to the amount of shared memory (I load that data from a file but I am using posix_fadvise(fd,0,0,POSIX_FADV_DONTNEED) to ensure this file is not cached and I made sure that it is working as expected). As far as I know SHM memory was not tagged as cache memory with kernel 2.6.9.If it is the case it is really unfortunate since normally cache memory can be considered to be part of the "available" memory since it can be flushed promptly but this is clearly not the case with SHM memory... Is there an easy way to get the total amount of used SHM memory on a system?
View 4 Replies View RelatedMy problem is I installed Zone Minder for camera security and I'm testing it on my laptop with the built in webcam and everything seems to work perfectly except when I try to view the live feed from the camera, it's just a black box. No video.
I checked this website and it's exactly the problem I'm having with a fix for it but his fix doesn't work. He says to type:
Code:
user@ubuntu:~$ sudo echo "256000000" > /proc/sys/kernel/shmmax
user@ubuntu:~$ sudo service apache2 restart
user@ubuntu:~$ sudo service zoneminder restart
But when I do the first line, I get this:
Code:
deemar@Clementine:~$ sudo echo "256000000" > /proc/sys/kernel/shmmax
bash: /proc/sys/kernel/shmmax: Permission denied
I just opened an (unmanaged) VPS account and and have been encountering nothing but problems with trying to get Apache up and running (its something I've done many times before).Basically the inital error was with LDAP not having enough space, so I disabled the related extensions and Apache still would not run. Looking at the log, it contains: (28)No space left on device: Unable to create scoreboard (anonymous shared memory failure)
View 1 Replies View RelatedI need to find the memory usage of a shared library loaded in Linux environment.
I need this information for deciding on whether to make the library part in to application or a seperate application itself.
I wrote a program that multiplies 2 matrices using multi-threads and another one using multiple processes and shared memory. Both in C.I need to find the total memory usage of these programs. I know of the top command, but when my matrices are relatively small they don't even show up on top because they complete so fast, how can I find the memory usage for these instances?Also, how can I find the total turnaround time of my programs
View 1 Replies View RelatedI use many different terminals during the course of my working day and frequently have to adjust my interaction to each unique type. For example, when interacting with bash via my work gnome-terminal I can use ctrl-arrow to skip over words, like most test editors allow. On the other hand, my xterm at home can't interpret this action and spits out a chunk of binary gibberish whenever I use this command.
I think that the behaviour of bash is consistent, it's just that the xterms treat keyboard events differently, depending on their configuration. Can someone confirm for me that this correct?, if yes, how can I calibrate the terminal to treat my keystrokes in the manner I desire?
I have Timidity++ 2.12.0 in Windows and a Soundfont customized by myself named Collection.sf2. everything I had to write in Timidity.cfg file was:
dir ctimidity
dir ctimiditysndfont
soundfont Collection.sf2
And just with that Timidity recognizes all presets in all banks of my soundfont. (This soundfont has more than 600 presets in more than 30 different banks.) I tried Timidity++ 2.13 for Windows with the same soudnfont and cfg file and it didn't work. 2.13 version recognized only the 127 presets of the first bank. so I went back to 2.12.0 version. The same now happens when I installed Timidity in Opensuse. etc/timidity.cfg file points to /usr/share/timidity/timidity.cfg file. In this last file I wrote the following:
dir /home/fernando/Soundfonts
soundfont Collection.sf2
I connected Rosegarden to Timidity and tried presets from several banks that use to be recognized automatically when I connect Rosegarden to Qsynth. But in Timidity no matter what bank I choose the sound comes only from the presets of the first bank. I tried the same connecting vkybd (a virtual midi keyboard found in multimedia repo) to timidity and even if i choose bank 2, 8, 16... the sound is always from instrumens of bank 0. it seems that Timidity 2.12 was the only version that recognized bank variations automatically just like Qsynth does. I could not succeed in this in any later version, neither in Windows nor in Linux.
Now I've got debug, default, desktop, ec2, trace, vanilla, xen installed im my system. I usually only boot with desktop, and I was wondering if it is OK to remove other stuff except debug, default, and desktop.
View 4 Replies View RelatedI am using Fedora 8 in my PC and i'm trying to create a shared memory (below is the sample program) i'm getting error while creating shared memory. Can anyone pl tell what is the possible cause for this.
View 2 Replies View RelatedI have visited these boards a few times, but never posted. Here's my problem: I was given the source to a program and asked to get it running on a 64-bit Debian 2.6.26 machine. Currently it is working on 2 64-bit OpenSUSE machines.
The application uses TCL TK for a GUI and everything compiles just fine; however, on startup, the user must enter one of three possible modules to load; when attempting to load these modules (tcl 'load' function), I receive this error:
Code:
Error in startup script: couldn't load file "../Build/libMpf.so": libTransReaders.so: cannot open shared object file: No such file or directory
while executing
"load ../Build/libMpf.so Mpf"
("eval" body line 1)
invoked from within
"eval load ../Build/${px}${i}${sx} $i"
[Code]...
I have 2 questions... I couldn't find answers by Googling (more precisely, by Blackling) and in GCC documents, so I'm asking here.
1. There are 2 flags for position independent code, -fpic and -fPIC. All the examples I read use -fPIC... so when is -fpic useful and what is the difference?
2. Some tutorials use "g++ -shared" while others use "ld" for the creation of the shared library. Why? Does it matter which method I use? Is there a difference? Why does nobody mention both options?
I'm running 11.2 with standard repositories (plus packman). I want to install a recent kernel and then compile some variations of it (to investigate a hardware problem).
So I took these steps:
(1) add the 11.2 Kernel:/HEAD repository
(2) enable multiversion in zypp.conf
(3) use YaST software management to select the kernel development pattern
Note that at the moment, the standard 11.2 kernel ( 2.6.31.14-0.6-desktop) is in use and I have not selected any packages from HEAD. But it has installed 2.6.37-41.1 versions of all the kernel packages I didn't already have (source & docs etc) instead of the 2.6.31 versions. /usr/src/linux symlinks to linux-2.6.37-41 instead of to a directory for the running kernel!
(1) it should have loaded the packages corresponding to the running kernel
(2) it's not supposed to switch repositories