Red Hat / Fedora :: Unable To Remove Shared Memory?
Aug 20, 2010
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.
I 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"?!
I 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.
Linux OS : Fedora 10 (No graphical mode)Windows OS : XP and Windows Server NT...I am able to access from my windows to linux using following step//fedora10 ip username of admin and password...I am able to view the admin and shared printer of fedora 10.When i try to enter in the admin folder i am not able to access it. It is giving error "Access is denied".
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.
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.
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?
Any 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()')
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 just got my network to work on Fedora, and now I have run into an new problem... I can't access any shared files or printers. The computer that has the printer and the files I want to access runs windows XP Home edition, and when I boot into XP on my machine, I can access the files and printer. Can this be fixed, or is Fedora incompatable with Windows XP in this case?
When 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.
How 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).
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
My 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
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)
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))
I am having a problem recognizing the full 24GB memory on a dell PowerEdge R610 system I just purchased. This is the Fedora 11 preview version, uname -a returns this:Linux comp1 2.6.29.3-140.fc11.x86_64 #1 SMP Tue May 12 10:44:27 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux
this is the off the shelf box from Dell and it is a quad-core with 24GB memory, but the OS can only recognize about 3GB, here is the free -m
total used free shared buffers cached Mem: 2980 607 2373 0 24 176
the system is otherwise functioning normal. how to get the full 24GB of mem recognized?
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
I've recently installed Fedora 12 from the Live CD as a new virtual machine using VMware. The issue I'm having is that when I go into the "Add/Remove Software" package manager, everything is blank. I'm guessing this is probably a proxy issue as I do connect to the internet via a proxy server.
I was recently learning to compile software from source code(tar.gz) files,he instructions told me to extract the files to the desktop. After I did this, I now see the folder on the desktop with the files in it, and I am unable to delete the folder. The error message says "there was an error deleting copying". Error removing file:Permission denied. Has anyone ever experienced this? I've run out of ideas as to how to get rid of it
I had F15 with hard drive encryption.I am now trying to move this hard drive to another laptop and install Windows.Even after complete formatting, the grub> still remains on this hard drive, which perhaps means that MBR is not wiped out. (Eventually Windows install fails)How can I format this HD as fresh, with single NTFS partition?have tried dd on linux, as well has MiniTool partition wizard on windows for formatting
I am looking to buy some memory for my netbook. Currently I have 1 GB of DDR3 memory. However, the specification says that 2 GB of memory is the max. However, when I do the following it says that 4GB is the max:
