Programming :: What's Share Memory Technology?
Jan 24, 2011what's the share memory technology?when did this technology appear?what are the key steps in c programming to use shm?
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Programming :: Synchronization Of Two Processes With Share Memory?
Feb 27, 2011I have two processes that share a piece of memory, and i want to use the shared memory to send data from one process to the other. it's like a simple consumer-producer problem. when the producer fills the shared memory, it waits until the consumer can consume some data in the memory; the consumer needs to wait if there is no data in the memory. The thing gets complicated when both threads are allowed to sleep and wait for the other to wake it up.
i wanted to use condition variable of pthread for synchronization, but it doesn't work in multiple processes. i tried semaphore, but it's quite complicated and i still cannot make it right. I believe it's a common problem and someone should have written similar code before, or maybe the code is even wrapped in a library, but when I search for it on Internet, I only found information about how to share memory between processes. Does anyone know where I can find this kind of code or library?
Programming :: Proposal For Symbolic Link Technology?
Sep 12, 2010Consider that symbolic links at times can be broken. The target reference can be lost or misplaced. As such, usage of a symbolic link becomes deterred or broken. I propose the following: Symbolic links from now on carry a checksum relating to the original file they are linked to. The original file will carry a property that checks if it has been changed. This property will figure out the new checksum, reconfigure the symbolic link, and continue the symbolic link. Furthermore, if the system were to change, there would exist the possibility of have a symblink-comparison feature that allows the user to check the entire filesystem for files that meet the checksum criteria so that symbolic links can once more be re-established.
View 2 Replies View RelatedProgramming :: Memory Leaks - Glibc Detected - ./SuffixTree: Malloc() - Memory Corruption - 0x00
Mar 21, 2011I 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.
Programming :: Write A Script That Can Show Me Total Memory Vs Used Memory?
Apr 13, 2010How 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 RelatedProgramming :: SHM Memory Counted As Cache Memory With Kernel 2.6.18?
Aug 25, 2010Is 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 RelatedFedora Servers :: How To Configure LDAP Technology
Mar 20, 2009How to configure ldap technology in fedora & linux.
View 3 Replies View RelatedUbuntu Multimedia :: Can Activate Dolby Technology
Jan 5, 2011Basically my portable computer's speakers have "Dolby Home Theater - Virtual Surround Sound" written on them. Now I figure there has to be some software (in Windows) that controls the whole thing. Is there something similar that in Ubuntu?
View 4 Replies View RelatedFedora :: Use The New SPICE VDI Technology To Create A Dummy Terminal?
Dec 14, 2010I have a pretty powerful desktop running fedora and was wondering if I could use the new SPICE VDI technology to create a dummy terminal virtual desktop using just a 2nd monitor, keyboard, and mouse (no thin client). Is this possible using USB ports? Would I need a 2nd video card for the monitor?
View 1 Replies View RelatedGeneral :: Performance - Best Available Technology For Layered Disk Cache
Oct 17, 2010I've just bought a 6-core Phenom with 16G of RAM. I use it primarily for compiling and video encoding (and occassional web/db). I'm finding all activities get disk-bound and I just can't keep all 6 cores fed. I'm buying an SSD raid to sit between the HDD and tmpfs. I want to setup a "layered" filesystem where reads are cached on tmpfs but writes safely go through to the SSD. I want files (or blocks) that haven't been read lately on the SSD to then be written back to a HDD using a compressed FS or block layer.
So basically reads:
- Check tmpfs
- Check SSD
- Check HD
And writes: - Straight to SSD (for safety), then tmpfs (for speed) And periodically, or when space gets low: - Move least frequently accessed files down one layer. I've seen a few projects of interest. CacheFS, cachefsd, bcache seem pretty close but I'm having trouble determining which are practical. bcache seems a little risky (early adoption), cachefs seems tied to specific network filesystems. There are "union" projects unionfs and aufs that let you mount filesystems over each other (USB device over a DVD usually) but both are distributed as a patch and I get the impression this sort of "transparent" mounting was going to become a kernel feature rather than a FS.
I know the kernel has a built-in disk cache but it doesn't seem to work well with compiling. I see a 20x speed improvement when I move my source files to tmpfs. I think it's because the standard buffers are dedicated to a specific process and compiling creates and destroys thousands of processes during a build (just guessing there). It looks like I really want those files precached.....
Ubuntu :: Which Technology Is Best To Get Break In Computer Networking Program?
Jul 30, 2010For a beginner, which technology is best to get a break in computer networking program?cisco,Microsoft or Linux?
View 5 Replies View RelatedProgramming :: Memory Leak In C++?
Mar 3, 2011I'm currently developping a program in C++, using Qt, for an embedded board (SBC9261).It works well but crashes after some time, due to a system memory overload (my program uses more and more memory until 100%, when it crashes).I've been able to figure out the source of the memory leak :The function f is called by my program every second. f instanciates a new object (a QImage from the Qt lib), does a bunch of processing on it, and returns it to the calling function :
Code:
QImage *MyClass::f(QString filename) {// Open image
QImage *image = new QImage(filename);
[code]....
Programming :: Regarding Memory Errors In G++?
Jul 22, 2011I have a general question regarding memory errors. I frequently ran into memory errors such as seg fault, double free, etc. Sometimes I got the following traces for example.
*** glibc detected *** /mnt/click: free(): invalid pointer: 0xb7ed8450 ***
======= Backtrace: =========
/lib/libc.so.6[0xb7dff905]
/lib/libc.so.6[0xb7e011a3]
[code]....
Then, I just run gdb, valgrind things and suddenly I started ask questions myself that what are those traces and how can I analyze?
Programming :: How To Get Usage Of CPU Memory?
Jan 11, 2009i am wondering How to get usage of CPU, Memory in linux environment? So would you able to tell me the ways?
View 10 Replies View RelatedProgramming :: Shared Memory IPC Variations ?
Apr 19, 2010I 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 Replies View RelatedProgramming :: Getting The CPU & (Virtual) Memory Of A Process?
Aug 23, 2010Is there any program which gets the CPU and memory of a process ?
View 1 Replies View RelatedProgramming :: Pthread Not Release Memory
Jan 1, 2011I have faced a problem with my code (a small tcp server). After the thread returns, the memory not decreases, but when a new connection is made, memory not increases and the new connection initialize a new thread with a same thread id of the previous thread. When two connections are made at same time, two thread ids are created and when the respective threads returns the memory not decreases. The Valgrind indicates that not memory leak occurs, the pointers are released. Indeed, more memory are allocate when new thread id is created. i used gcc and debian.
[Code]....
Programming :: Process Memory Allocation
Apr 30, 2011I have been assigned a school project on detecting memory leaks in linux processes. I am reading.. but have found it hard and inefficient to go through the very vast documentation not knowing what to really look for. Could you please give me some guidelines on this subject?
View 4 Replies View RelatedProgramming :: Byte At Memory Location 45 With Immediate Value 03
Jul 10, 2011As 2.17
I want to code this:
and byte[45],03
In words, AND the byte at memory location 45 with immediate value 03. As reports "Ambiguous operand size for and". How could I code the instruction such that as understands my intention?
john: .byte 45
and byte[john],03
gives the same error.
Programming :: Creating A Memory Leak In C++?
Dec 16, 2010I need to write a small program that eats away at availabe memory. I need to creaty a memory leak to test how other programs cope. I need to run this program on linux and see if the available memory is decreasing.
So I have done:
Code:
int main()
{
int *buffer;
while(1)
[Code]...
Programming :: How To Do A Direct Memory Access
Jul 26, 2011I have a single board computer previously running DOS. I recently made Linux running on it. Now that the system is running Linux, I have to translate the code that was supported by DOS. The code has segments that allow direct access of memory mapped registers through the macro _MK_FP and do read/write. I have read that where DOS allows this kind of direct memory access, Linux does not. Is there a way to do this in Linux?
View 6 Replies View RelatedProgramming :: Memory Allocation For Struct In C++?
Mar 30, 2010How do we allocate memory of struct? what i did was
Code:
int main()
struct amp
{
[code].....
cout <<"The size of 'struct' is"<< sizeof(struct amp)<<"and it is located at"<<struct amp*s = malloc(sizeof(struct amp))<<endl;
it gives me an error---
In funtion 'int main()':
error: expected primary-expression before 'struct'
error: expected ';' before 'struct'
Programming :: Memory Video Driver ?
Feb 9, 2010I have have to write a video device driver, but rendering will happening in memory, not on a physical card. I already wrote a simple driver stripping out hardware piece code from an existent vodoo driver. I an install it, uninstall it but i dont know how to map it to a file /dev/mydevice_video
Is there a field in fb_info or fb_vscreenifo where the device name has to be passed before calling register_framebuffer.
Programming :: Phys_to_virt For High Memory?
Oct 18, 2010I have a kernel module that I am trying to do a phys_to_virt() and then perform a memcpy to the returned virtual address. The problem that I'm having is that my module crashes during the memcpy when trying to do this on a physical address in high memory. Do I need to need to perform some kind a mapping operation on high memory address for this to work?
View 1 Replies View RelatedProgramming :: Pthread Memory Not Being Freed?
Apr 19, 2010I have an application that has pretty large memory profile. The general program flow is as follows:
Code:
main:
do 10 times:
[code]....
Programming :: Save A Packet In The Memory
Feb 7, 2011i'm sniffing network packets with pcap in ubuntu, i need to save these packets somewhere in the memory and after a while read ans send them. how can i do this?
View 1 Replies View RelatedProgramming :: Seg Fault But No Memory References?
Apr 25, 2011I can't figure out why I'm getting seg fault in this program im making in c++. The program is of the game "Mastermind" board game which I'm sure many of you might have heard of.im fairly new to coding c++. I do not know why I'm getting seg fault error when trying to compile as I'm not using any pointers? or trying to access memory that was not allocated to me?
View 5 Replies View RelatedProgramming :: Memory Optimization For Child Processes?
Sep 6, 2010I work on Linux for ARM processor for cable modem. There is a tool that I have written (as the job demands) that sends/storms customized UDP packets using raw sockets. I form the packet from scratch so that we have the flexibility to play with different options. This tool is mainly for stress testing routers.
The details are here.
I actually have multiple interfaces created. Each interface will obtain IP addresses using DHCP. This is done in order to make the modem behave as virtual customer premises equipment (vcpe).
When the system comes up, I start those processes that are asked to. Every process that I start will continuously send packets. So process 0 will send packets using interface 0 and so on. Each of these processes that send packets would allow configuration (change in UDP parameters and other options at run time). Thats the reason I decide to have separate processes.
I start these processes using fork and excec from the provisioning processes of the modem.
The problem now is that each process takes up a lot of memory. Starting just 3 such processes, causes the system to crash and reboot.
I have tried the following:- 1-I have always assumed that pushing more code to the Shared Libraries will help. So when I tried moving many functions into shared library and keeping minimum code in the processes, it made no difference to my surprise.
2-I also removed all arrays and made them use the heap. However it made no difference. This maybe because the processes runs continuously and it makes no difference if it is stack or heap?
3-I suspect the process from I where I call the fork is huge and that is the reason for the processes that I make result being huge. I am not sure how else I could go about. say process A is huge -> I start process B by forking and excec. B inherits A's memory area. So now I do this -> A starts C which inturn starts B will also not help as C still inherits A?. I used vfork as an alternative which did not help either. I do wonder why.
reduce the memory used by each independent child processes.
Programming :: Access In-memory Structure And Its Members?
Dec 13, 2010I am implementing c program to access ext3 file system's metadata. I want to know how to access members of the in-memory superblock structure. I am able access on-disk ext3_super_block structure but dont know how to access in- memory structure and its members.
View 1 Replies View RelatedProgramming :: Access Another Process's Memory With A Twist?
Jul 31, 2010I have been looking for a method for a while now that would allow me to access another process's memory without causing it to freeze. But with all of my googling I have found nothing
so, my question is: Is there a way to not lock a process while accessing it's "/proc/[PID]/mem" interface?