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  • Pointer Implementation Details in C

    - by Will Bickford
    I would like to know architectures which violate the assumptions I've listed below. Also I would like to know if any of the assumptions are false for all architectures (i.e. if any of them are just completely wrong). sizeof(int *) == sizeof(char *) == sizeof(void *) == sizeof(func_ptr *) The in-memory representation of all pointers for a given architecture is the same regardless of the data type pointed to. The in-memory representation of a pointer is the same as an integer of the same bit length as the architecture. Multiplication and division of pointer data types are only forbidden by the compiler. NOTE: Yes I know this is nonsensical. What I mean is - is there hardware support to forbid this incorrect usage? All pointer values can be casted to a single integer. In other words, what architectures still make use of segments and offsets? Incrementing a pointer is equivalent to adding sizeof(the pointed data type) to the memory address stored by the pointer. If p is an int32* then p+1 is equal to the memory address 4 bytes after p. I'm most used to pointers being used in a contiguous, virtual memory space. For that usage, I can generally get by thinking of them as addresses on a number line. See (http://stackoverflow.com/questions/1350471/pointer-comparison/1350488#1350488).

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  • read-only memory and heap memory

    - by benjamin button
    hi, AFAIK, string literals are stored in read only memory in case of C language. where is this actually present on the hardware. as per my knowledge heap is on RAM.correct me if i am wrong. how different is heap from read only memory? is it OS dependant?

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  • iPhone memory management

    - by Prazi
    I am newbie to iPhone programming. I am not using Interface Builder in my programming. I have some doubt about memory management, @property topics in iPhone. Consider the following code @interface LoadFlag : UIViewController { UIImage *flag; UIImageView *preview; } @property (nonatomic, retain) UIImageView *preview; @property (nonatomic, retain) UIImage *flag; @implementation @synthesize preview; @synthesize flag; - (void)viewDidLoad { flag = [UIImage imageNamed:@"myImage.png"]]; NSLog(@"Preview: %d\n",[preview retainCount]); //Count: 0 but shouldn't it be 1 as I am retaining it in @property in interface file preview=[[UIImageView alloc]init]; NSLog(@"Count: %d\n",[preview retainCount]); //Count: 1 preview.frame=CGRectMake(0.0f, 0.0f, 100.0f, 100.0f); preview.image = flag; [self.view addSubview:preview]; NSLog(@"Count: %d\n",[preview retainCount]); //Count: 2 [preview release]; NSLog(@"Count: %d\n",[preview retainCount]); //Count: 1 } When & Why(what is the need) do I have to set @property with retain (in above case for UIImage & UIImageView) ? I saw this statement in many sample programs but didn't understood the need of it. When I declare @property (nonatomic, retain) UIImageView *preview; statement the retain Count is 0. Why doesn't it increase by 1 inspite of retaining it in @property. Also when I declare [self.view addSubview:preview]; then retain Count increments by 1 again. In this case does the "Autorelease pool" releases for us later or we have to take care of releasing it. I am not sure but I think that the Autorelease should handle it as we didn't explicitly retained it so why should we worry of releasing it. Now, after the [preview release]; statement my count is 1. Now I don't need UIImageView anymore in my program so when and where should I release it so that the count becomes 0 and the memory gets deallocated. Again, I am not sure but I think that the Autorelease should handle it as we didn't explicitly retained it so why should we worry of releasing it. What will happen if I release it in -(void) dealloc method In the statement - flag = [UIImage imageNamed:@"myImage.png"]]; I haven't allocated any memory to flag but how can I still use it in my program. In this case if I do not allocate memory then who allocates & deallocates memory to it or is the "flag" just a reference pointing to - [UIImage imageNamed:@"myImage.png"]];. If it is a reference only then do i need to release it. Thanks in advance.

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  • ARC, worth it or not?

    - by MSK
    When I moved to Objective C (iOS) from C++ (and little Java) I had hard time understanding memory management in iOS. But now all this seems natural and I know retain, autorelease, copy and release stuff. After reading about ARC, I am wondering is there more benefits of using ARC or it is just that you dont have to worry about memory management. Before moving to ARC I wanted to know how worth is moving to ARC. XCode has "Convert to Objective C ARC" menu. Is the conversion is that simple (nothing to worry about)? Does it help me in reducing my apps memory foot-print, memory leaks etc (somehow ?) Does it has much testing impact on my apps ? What are non-obvious advantages? Any Disadvantage os moving to it?

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  • Php efficiency question --> Database call vs. File Write vs. Calling C++ executable

    - by JP19
    Hi, What I wish to achieve is - log all information about each and every visit to every page ofmy website (like ip address, browser, referring page, etc). Now this is easy to do. What I am interested is doing this in a way so as to cause minimum overhead (runtime) in the php scripts. What is the best approach for this efficiency-wise: 1) Log all information to a database table 2) Write to a file (from php directly) 3) Call a C++ executable, that will write this info to a file in parallel [so the script can continue execution without waiting for the file write to occur ...... is this even possible] I may be trying to optimize unnecessarily/prematurely, but still - any thoughts / ideas on this would be appreciated. (I think efficiency of file write/logging can really be a concern if I have say 100 visits per minute...) Thanks & Regards, JP

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  • Linux configurations that would affect Java memory usage?

    - by wmacura
    Hi, Background: I have a set of java background workers I start as part of my webapp. I develop locally on Ubuntu 10.10 and deploy to an Ubuntu 10.04LTS server (a media temple (ve) instance). They're both running the same JVM: Sun JVM 1.6.0_22-b04. As part of the initialization script each worker is started with explicit Xmx, Xms, and XX:MaxPermGen settings. Yet somehow locally all 10 workers use 250MB, while on the server they use more than 2.7GB. I don't know how to begin to track this down. I thought the Ubuntu (and thus, kernel) version might make a difference, but I tried an old 10.04 VM and it behaves as expected. I've noticed that the machine does not seem to ever use memory for buffer or cache (according to htop), which seems a bit strange, but perhaps normal for a server? (edited) Some info: (server) root@devel:/app/axir/target# uname -a Linux devel 2.6.18-028stab069.5 #1 SMP Tue May 18 17:26:16 MSD 2010 x86_64 GNU/Linux (local) wiktor@beastie:~$ uname -a Linux beastie 2.6.35-25-generic #44-Ubuntu SMP Fri Jan 21 17:40:44 UTC 2011 x86_64 GNU/Linux (edited) Comparing PS output: (ps -eo "ppid,pid,cmd,rss,sz,vsz") PPID PID CMD RSS SZ VSZ (local) 1588 1615 java -cp axir-distribution. 25484 234382 937528 1615 1631 java -cp /home/wiktor/Code/ 83472 163059 652236 1615 1657 java -cp /home/wiktor/Code/ 70624 89135 356540 1615 1658 java -cp /home/wiktor/Code/ 37652 77625 310500 1615 1669 java -cp /home/wiktor/Code/ 38096 77733 310932 1615 1675 java -cp /home/wiktor/Code/ 37420 61395 245580 1615 1684 java -cp /home/wiktor/Code/ 38000 77736 310944 1615 1703 java -cp /home/wiktor/Code/ 39180 78060 312240 1615 1712 java -cp /home/wiktor/Code/ 38488 93882 375528 1615 1719 java -cp /home/wiktor/Code/ 38312 77874 311496 1615 1726 java -cp /home/wiktor/Code/ 38656 77958 311832 1615 1727 java -cp /home/wiktor/Code/ 78016 89429 357716 (server) 22522 23560 java -cp axir-distribution. 24860 285196 1140784 23560 23585 java -cp /app/axir/target/a 100764 161629 646516 23560 23667 java -cp /app/axir/target/a 72408 92682 370728 23560 23670 java -cp /app/axir/target/a 39948 97671 390684 23560 23674 java -cp /app/axir/target/a 40140 81586 326344 23560 23739 java -cp /app/axir/target/a 39688 81542 326168 They look very similar. In fact, the question now is why, if I add up the virtual memory usage on the server (3.2GB) does it more closely reflect 2.4GB of memory used (according to free), yet locally the virtual memory used adds up to a much more substantial 4.7GB but only actually uses ~250MB. It seems that perhaps memory isn't being shared as aggressively. (if that's even possible) Thank you for your help, Wiktor

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  • New 64 bit linux system has regular processes (ps, grep etc) taking up way too much VIRT mem

    - by user42980
    We just moved from a 32-bit machine to a 64-bit machine. We have quickly ran out of memory despite the new boxes have twice as much ram as the old boxes. Running a simple ps command will illustrate the problem. New machine: 132 prod-Charlotte1-node1 ~/public_html/rearch/cgi-bin ps aux | grep ps root 293 0.0 0.0 0 0 ? S< May09 0:00 [kpsmoused] xamine 2267 1.0 0.0 63728 928 pts/3 R+ 16:50 0:00 ps aux xamine 2268 0.0 0.0 61172 752 pts/3 S+ 16:50 0:00 grep ps Old machine: 132 prod-116431-node1:/home/xamine ps aux | grep ps xamine 23191 0.0 0.0 2332 768 pts/6 R+ 15:41 0:00 ps aux xamine 23192 0.0 0.0 3668 692 pts/6 S+ 15:41 0:00 grep ps Notice that the ps process is using 63M of VIRT mem vs 2 on the old machine. New Machine: Enterprise Linux Enterprise Linux Server release 5.4 (Carthage) Red Hat Enterprise Linux Server release 5.4 (Tikanga) Old Machine: Red Hat Enterprise Linux ES release 4 (Nahant Update 4) Thanks for any thoughts you have!

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  • Any dangers in using DDR memory with a higher frequency than the FSB?

    - by raw_noob
    I'm looking to upgrade memory in an older motherboard. The processor is an AMD Sempron 2500+ with a maximum speed of 333/166MHz. The motherboard is an MSI MS-7061 (KV3M-V), which accepts up to 2Gb of DDR memory maximum PC2700 in 2 slots and has a maximum FSB of 333MHz. The board does not have dual-channel support. Existing memory includes a stick of 512Mb PC3200, which seems to be running OK (presumably at PC2700) but is rated 200MHz, which is below the FSB speed. The other stick is 256Mb PC2100/133MHz, again below the FSB speed. (All figures from CPU-Z.) I have a chance to acquire a single used stick of PC3200/400MHz memory very cheaply. Crucial's system scanner seems to suggest that this will be OK with my system, but other sites have suggested that running memory with a higher frequency than the FSB can cause instability. Is this true? Would I be better waiting until I can buy the correct PC2700/333MHz stick? I'm assuming that the mixed memory I have at present is running as 768Mb at 133MHz. Is this a reasonable assumption? If so, would you expect the performance differences between 768Mb/133MHz and 1Gb/333MHz to be very noticeable? If I install the new 1Gb/400 or 333MHz stick in slot 1, am I right in thinking that adding back the existing 512Mb/200MHz stick in slot 2 would pull the whole 1.5Gb system memory speed down to 200MHz? If so, which would be better - 1.5Gb/200MHz, or the single 1Gb stick at the full 333MHz that the FSB permits? Is more headroom more important than extra speed? Any help - or even opinions - gratefully received. I can't find reliable information, and I can't afford to make expensive mistakes.

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  • Why do I get swap space related errors when I still have lots of free memory in Solaris 10?

    - by Tom Duckering
    I am seeing a few of my services suffering/crashing with errors along the lines of "Error allocating memory" or "Can't create new process" etc. I'm slightly confused by this since logs show that at the time the system has lots of free memory (around 26GB in one case) of memory available and is not particularly stressed in any other way. After noting a JVM crash with similar error with the added query of "Out of swap space?" it made me dig a little deeper. It turns out that someone has configured our zone with a 2GB swap file. Our zone doesn't have capped memory and currently has access to as much of the 128GB of the RAM as it need. Our SAs are planning to cap this at 32GB when they get the chance. My current thinking is that whilst there is memory aplenty for the OS to allocate, the swap space seems grossly undersized (based on other answers here). It seems as though Solaris is wanting to make sure there's enough swap space in case things have to swap out (i.e. it's reserving the swap space). Is this thinking right or is there some other reason that I get memory allocation errors with this large amount of memory free and seemingly undersized swap space?

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  • How much free memory should I have on my webserver?

    - by neanderslob
    I have a webserver that's currently hosting two Wordpress sites and some java-based collaboration software. The server has 2G of memory and is currently using about 1.8G of the available memory. Right now what's on here is pretty much a pilot project that's getting negligible traffic so I think it's pretty clear that I'll be needing more memory. I was wondering, if I was to release it, how I might anticipate my memory needs based on the traffic it gets. I've poked around on Google and what I've found has been a bit tenuous. Is there a good heuristic that one should use when calculating memory demands as a function of the base (no traffic) load on the server? For reference, the output of free -m can be seen below: total used free shared buffers cached Mem: 2048 1832 215 0 0 0 -/+ buffers/cache: 1832 215 Swap: 0 0 0 To me this looks like actual memory used and isn't an illusion due to caching or anything else. I figure the demands of my collaboration software will have to be experimentally tested so here's free -m without that software running: total used free shared buffers cached Mem: 2048 1109 938 0 0 0 -/+ buffers/cache: 1109 938 Swap: 0 0 0 My plan B to figure this out is to add a bunch of swap space to the server, give it some traffic and adjust according the the amount that swap gets used. I was just wondering if anyone had a good rule of thumb to estimate how much memory I should plan on in advance...or if what I'm thinking is nuts. Many thanks in advance (I'm really quite new to this).

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  • WPF 3.5 RenderTargetBitmap memory hog

    - by kingRauk
    I have a 3.5 WPF application that use's RenderTargetBitmap. It eat's memory like a big bear. It's is a know problem in 3.5 that RenderTargetBitmap.Render has memory problems. Have find some solutions for it, but i doesnt help. https://connect.microsoft.com/VisualStudio/feedback/details/489723/rendertargetbitmap-render-method-causes-a-memory-leak Program takes too much memory And more... Does anyway have any more ideas to solve it... static Image Method(FrameworkElement e, int width, int height) { const int dpi = 192; e.Width = width; e.Height = height; e.Arrange(new Rect(0, 0, width, height)); e.UpdateLayout(); if(element is Graph) (element as Graph).UpdateComponents(); var bitmap = new RenderTargetBitmap((int)(width*dpi/96.0), (int)(height*dpi/96.0), dpi, dpi, PixelFormats.Pbgra32); bitmap.Render(element); var encoder = new PngBitmapEncoder(); encoder.Frames.Add(BitmapFrame.Create(bitmap)); using (var stream = new MemoryStream()) { encoder.Save(stream); element.Clip = null; Dispose(element); bitmap.Freeze(); DisposeRender(bitmap); bitmap.Clear(); GC.Collect(); GC.WaitForPendingFinalizers(); return System.Drawing.Image.FromStream(stream); } } public static void Dispose(FrameworkElement element) { GC.Collect(); GC.WaitForPendingFinalizers(); GC.Collect(); } public static void DisposeRender(RenderTargetBitmap bitmap) { if (bitmap != null) bitmap.Clear(); bitmap = null; GC.Collect(); GC.WaitForPendingFinalizers(); }

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  • Instantiating class with custom allocator in shared memory

    - by recipriversexclusion
    I'm pulling my hair due to the following problem: I am following the example given in boost.interprocess documentation to instantiate a fixed-size ring buffer buffer class that I wrote in shared memory. The skeleton constructor for my class is: template<typename ItemType, class Allocator > SharedMemoryBuffer<ItemType, Allocator>::SharedMemoryBuffer( unsigned long capacity ){ m_capacity = capacity; // Create the buffer nodes. m_start_ptr = this->allocator->allocate(); // allocate first buffer node BufferNode* ptr = m_start_ptr; for( int i = 0 ; i < this->capacity()-1; i++ ) { BufferNode* p = this->allocator->allocate(); // allocate a buffer node } } My first question: Does this sort of allocation guarantee that the buffer nodes are allocated in contiguous memory locations, i.e. when I try to access the n'th node from address m_start_ptr + n*sizeof(BufferNode) in my Read() method would it work? If not, what's a better way to keep the nodes, creating a linked list? My test harness is the following: // Define an STL compatible allocator of ints that allocates from the managed_shared_memory. // This allocator will allow placing containers in the segment typedef allocator<int, managed_shared_memory::segment_manager> ShmemAllocator; //Alias a vector that uses the previous STL-like allocator so that allocates //its values from the segment typedef SharedMemoryBuffer<int, ShmemAllocator> MyBuf; int main(int argc, char *argv[]) { shared_memory_object::remove("MySharedMemory"); //Create a new segment with given name and size managed_shared_memory segment(create_only, "MySharedMemory", 65536); //Initialize shared memory STL-compatible allocator const ShmemAllocator alloc_inst (segment.get_segment_manager()); //Construct a buffer named "MyBuffer" in shared memory with argument alloc_inst MyBuf *pBuf = segment.construct<MyBuf>("MyBuffer")(100, alloc_inst); } This gives me all kinds of compilation errors related to templates for the last statement. What am I doing wrong?

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  • why pointer to pointer is needed to allocate memory in function

    - by skydoor
    Hi I have a segmentation fault in the code below, but after I changed it to pointer to pointer, it is fine. Could anybody give me any reason? void memory(int * p, int size) { try{ p = (int *) malloc(size*sizeof(int)); } catch( exception& e) { cout<<e.what()<<endl; } } it does not work in the main function as blow int *p = 0; memory(p, 10); for(int i = 0 ; i < 10; i++) p[i] = i; however, it works like this . void memory(int ** p, int size) { `//pointer to pointer` try{ *p = (int *) malloc(size*sizeof(int)); } catch( exception& e) { cout<<e.what()<<endl; } } int main() { int *p = 0; memory(&p, 10); //get the address of the pointer for(int i = 0 ; i < 10; i++) p[i] = i; for(int i = 0 ; i < 10; i++) cout<<*(p+i)<<" "; return 0; }

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  • When memory is actually freeded?

    - by zhyk
    Hello all. I'm trying to understand memory management stuff in Objective-C. If I see the memory usage listed by Activity Monitor, it looks like memory is not being freed (I mean column rsize). But in "Object Allocations" everything looks fine. Here is my simple code: #import <Foundation/Foundation.h> int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; NSInteger i, k=10000; while (k>0) { NSMutableArray *array = [[NSMutableArray alloc]init]; for (i=0;i<1000*k; i++) { NSString *srtring = [[NSString alloc] initWithString:@"string...."]; [array addObject:srtring]; [srtring release]; srtring = nil; } [array release]; array = nil; k-=500; } [NSThread sleepForTimeInterval:5]; [pool release]; return 0; } As for retain and release it's cool, everything is balanced. But rsize decreases only after quitting from this little program. Is it possible to "clean" memory somehow before quitting?

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  • Shared Memory and Process Sempahores (IPC)

    - by fsdfa
    This is an extract from Advanced Liniux Programming: Semaphores continue to exist even after all processes using them have terminated. The last process to use a semaphore set must explicitly remove it to ensure that the operating system does not run out of semaphores.To do so, invoke semctl with the semaphore identifier, the number of semaphores in the set, IPC_RMID as the third argument, and any union semun value as the fourth argument (which is ignored).The effective user ID of the calling process must match that of the semaphore’s allocator (or the caller must be root). Unlike shared memory segments, removing a semaphore set causes Linux to deallocate immediately. If a process allocate a shared memory, and many process use it and never set to delete it (with shmctl), if all them terminate, then the shared page continues being available. (We can see this with ipcs). If some process did the shmctl, then when the last process deattached, then the system will deallocate the shared memory. So far so good (I guess, if not, correct me). What I dont understand from that quote I did, is that first it say: "Semaphores continue to exist even after all processes using them have terminated." and then: "Unlike shared memory segments, removing a semaphore set causes Linux to deallocate immediately."

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  • Intel MKL memory management and exceptions

    - by Andrew
    Hello everyone, I am trying out Intel MKL and it appears that they have their own memory management (C-style). They suggest using their MKL_malloc/MKL_free pairs for vectors and matrices and I do not know what is a good way to handle it. One of the reasons for that is that memory-alignment is recommended to be at least 16-byte and with these routines it is specified explicitly. I used to rely on auto_ptr and boost::smart_ptr a lot to forget about memory clean-ups. How can I write an exception-safe program with MKL memory management or should I just use regular auto_ptr's and not bother? Thanks in advance. EDIT http://software.intel.com/sites/products/documentation/hpc/mkl/win/index.htm this link may explain why I brought up the question UPDATE I used an idea from the answer below for allocator. This is what I have now: template <typename T, size_t TALIGN=16, size_t TBLOCK=4> class aligned_allocator : public std::allocator<T> { public: pointer allocate(size_type n, const void *hint) { pointer p = NULL; size_t count = sizeof(T) * n; size_t count_left = count % TBLOCK; if( count_left != 0 ) count += TBLOCK - count_left; if ( !hint ) p = reinterpret_cast<pointer>(MKL_malloc (count,TALIGN)); else p = reinterpret_cast<pointer>(MKL_realloc((void*)hint,count,TALIGN)); return p; } void deallocate(pointer p, size_type n){ MKL_free(p); } }; If anybody has any suggestions, feel free to make it better.

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  • C when to allocate and free memory - before function call, after function call...etc

    - by Keith P
    I am working with my first straight C project, and it has been a while since I worked on C++ for that matter. So the whole memory management is a bit fuzzy. I have a function that I created that will validate some input. In the simple sample below, it just ignores spaces: int validate_input(const char *input_line, char* out_value){ int ret_val = 0; /*false*/ int length = strlen(input_line); cout << "length = " << length << "\n"; out_value =(char*) malloc(sizeof(char) * length + 1); if (0 != length){ int number_found = 0; for (int x = 0; x < length; x++){ if (input_line[x] != ' '){ /*ignore space*/ /*get the character*/ out_value[number_found] = input_line[x]; number_found++; /*increment counter*/ } } out_value[number_found + 1] = '\0'; ret_val = 1; } return ret_val; } Instead of allocating memory inside the function for out_value, should I do it before I call the function and always expect the caller to allocate memory before passing into the function? As a rule of thumb, should any memory allocated inside of a function be always freed before the function returns?

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  • Preallocating memory with C++ in realtime environment

    - by Elazar Leibovich
    I'm having a function which gets an input buffer of n bytes, and needs an auxillary buffer of n bytes in order to process the given input buffer. (I know vector is allocating memory at runtime, let's say that I'm using a vector which uses static preallocated memory. Imagine this is NOT an STL vector.) The usual approach is void processData(vector<T> &vec) { vector<T> &aux = new vector<T>(vec.size()); //dynamically allocate memory // process data } //usage: processData(v) Since I'm working in a real time environment, I wish to preallocate all the memory I'll ever need in advance. The buffer is allocated only once at startup. I want that whenever I'm allocating a vector, I'll automatically allocate auxillary buffer for my processData function. I can do something similar with a template function static void _processData(vector<T> &vec,vector<T> &aux) { // process data } template<size_t sz> void processData(vector<T> &vec) { static aux_buffer[sz]; vector aux(vec.size(),aux_buffer); // use aux_buffer for the vector _processData(vec,aux); } // usage: processData<V_MAX_SIZE>(v); However working alot with templates is not much fun (now let's recompile everything since I changed a comment!), and it forces me to do some bookkeeping whenever I use this function. Are there any nicer designs around this problem?

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  • How to optimize paging for large in memory database

    - by snakefoot
    I have an application where the entire database is implemented in memory using a stl-map for each table in the database. Each item in the stl-map is a complex object with references to other items in the other stl-maps. The application works with a large amount of data, so it uses more than 500 MByte RAM. Clients are able to contact the application and get a filtered version of the entire database. This is done by running through the entire database, and finding items relevant for the client. When the application have been running for an hour or so, then Windows 2003 SP2 starts to page out parts of the RAM for the application (Eventhough there is 16 GByte RAM on the machine). After the application have been partly paged out then a client logon takes a long time (10 mins) because it now generates a page fault for each pointer lookup in the stl-map. I can see it is possible to tell Windows to lock memory in RAM, but this is generally only recommended for device drivers, and only for "small" amounts of memory. I guess a poor mans solution could be to loop through the entire memory database, and thus tell Windows we are still interested in keeping the datamodel in RAM. I guess another poor mans solution could be to disable the pagefile completely on Windows. I guess the expensive solution would be a SQL database, and then rewrite the entire application to use a database layer. Then hopefully the database system will have implemented means to for fast access. Are there other more elegant solutions ?

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  • How to access variables in shared memory

    - by user1723361
    I am trying to create a shared memory segment containing three integers and an array. The segment is created and a pointer is attached, but when I try to access the values of the variables (whether changing, printing, etc.) I get a segmentation fault. Here is the code I tried: #include <stdio.h> #include <stdbool.h> #include <stdlib.h> #include <errno.h> #include <sys/types.h> #include <sys/ipc.h> #include <sys/sem.h> #define SIZE 10 int* shm_front; int* shm_end; int* shm_count; int* shm_array; int shm_size = 3*sizeof(int) + sizeof(shm_array[SIZE]); int main(int argc, char* argsv[]) { int shmid; //create shared memory segment if((shmid = shmget(IPC_PRIVATE, shm_size, 0644)) == -1) { printf("error in shmget"); exit(1); } //obtain the pointer to the segment if((shm_front = (int*)shmat(shmid, (void *)0, 0)) == (void *)-1) { printf("error in shmat"); exit(1); } //move down the segment to set the other pointers shm_end = shm_front + 1; shm_count = shm_front + 2; shm_array = shm_front + 3; //tests on shm //*shm_end = 10; //gives segmentation fault //printf("\n%d", *shm_front); //gives segmentation fault //clean-up //get rid of shared memory shmdt(shm_front); shmctl(shmid, IPC_RMID, NULL); //printf("\n\n"); return 0; } I tried accessing the shared memory by dereferencing the pointer to the struct, but got a segmentation fault each time.

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  • Identifying memory leaks in C++

    - by Dororo
    I've got the following bit of code, which I've narrowed down to be causing a memory leak (that is, in Task Manager, the Private Working Set of memory increases with the same repeated input string). I understand the concepts of heaps and stacks for memory, as well as the general rules for avoiding memory leaks, but something somewhere is still going wrong: while(!quit){ char* thebuffer = new char[210]; //checked the function, it isn't creating the leak int size = FuncToObtainInputTextFromApp(thebuffer); //stored in thebuffer string bufferstring = thebuffer; int startlog = bufferstring.find("$"); int endlog = bufferstring.find("&"); string str_text=""; str_text = bufferstring.substr(startlog,endlog-startlog+1); String^ str_text_m = gcnew String(str_text_m.c_str()); //some work done delete str_text_m; delete [] thebuffer; } The only thing I can think of is it might be the creation of 'string str_text' since it never goes out of scope since it just reloops in the while? If so, how would I resolve that? Defining it outside the while loop wouldn't solve it since it'd also remain in scope then too. Any help would be greatly appreciated.

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  • Oracle Unveils Breakthrough Technology: Database In-Memory

    - by Mala Narasimharajan
    Missed Larry Ellison's big announcement this morning? Today, Oracle announced . Oracle Database In-Memory.  Oracle Database In-Memory  transparently extends the power of Oracle Database 12c to enable organizations to discover business insights in real-time while simultaneously increasing transactional performance. Here's why you should care - this new breakthrough technology enables enterprises to get faster answers to business questions ultimately leading to faster business action. Oracle Database In-Memory delivers leading-edge in-memory performance without the need to restrict functionality or accept compromises, complexity and risk. Deploying Oracle Database In-Memory with virtually any existing Oracle Database-compatible application is as easy as flipping a switch--no application changes are required.  For more information on Oracle Database In-Memory go to http://www.oracle.com/us/corporate/press/2215795

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  • Handle php out of memory error

    - by PeterMmm
    I have a Drupal based web site on a relative small vserver (512MB RAM). Recently the website begins to return php out of memory messages like this: Fatal error: Out of memory (allocated 17039360) (tried to allocate 77824 bytes) in /home/... All php.ini memory limit parameters are set to off (-1). Propably the website has gained of complexity, content, etc. But I cannot interpret fine that message: Does that mean that the whole request has allocated 17MB(?) right now and cannot get 7MB(?) more from the OS. Has the web server spend all memory or has the OS no more memory to allocate ? I'm not shure if the memory overhead is coming from the web server or another service, because when I get the out-of-memoy message I can't get into the server with ssh. After a while all runs fine again.

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  • swapping or trashing with vast amounts of unmapped pagecache

    - by Marco
    I'm using kubuntu jaunty (i386 32bit), kernel 2.6.28-13-generic. I've 4Gb of RAM, of which only 3317Mb are seen by the system (I guess because of the 32bit system). I'm seeing that the pagecache utilization is continually growing, up to the point that the system is unusable (after a few days). This happens also when I don't do anything (all user applications closed and the bare minimum of services enabled). If enabled, the system starts to use swap space (using it all in the end). Even if swap is disabled, disk activity becomes continuous, with the system unresponsive. For example, right now the system is working (albeit a tad slow), with only Firefox and wing ide running, and I have 2Gb cached with only 45Mb mapped: $ free total used free shared buffers cached Mem: 3346388 3247328 99060 0 8416 2117980 -/+ buffers/cache: 1120932 2225456 Swap: 2144668 519448 1625220 $ cat /proc/meminfo MemTotal: 3346388 kB MemFree: 97128 kB Buffers: 7872 kB Cached: 2120224 kB SwapCached: 413860 kB Active: 2304596 kB Inactive: 865984 kB Active(anon): 2279168 kB Inactive(anon): 830236 kB Active(file): 25428 kB Inactive(file): 35748 kB Unevictable: 32 kB Mlocked: 32 kB HighTotal: 2492940 kB HighFree: 5456 kB LowTotal: 853448 kB LowFree: 91672 kB SwapTotal: 2144668 kB SwapFree: 1625244 kB Dirty: 84 kB Writeback: 0 kB AnonPages: 629304 kB Mapped: 45768 kB Slab: 45600 kB SReclaimable: 21756 kB SUnreclaim: 23844 kB PageTables: 4468 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 3817860 kB Committed_AS: 3735020 kB VmallocTotal: 122880 kB VmallocUsed: 9352 kB VmallocChunk: 66600 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 4096 kB DirectMap4k: 16376 kB DirectMap4M: 888832 kB If I try to drop the caches, little happens: # sync ; echo 3 > /proc/sys/vm/drop_caches ; free total used free shared buffers cached Mem: 3346388 3220580 125808 0 3020 2100600 -/+ buffers/cache: 1116960 2229428 Swap: 2144668 519356 1625312 Right now I've vm.swappiness = 5, but I've tried also with 0 and 1 (without noticeable differences). I've also tried vm.vfs_cache_pressure = 50 and 150 (again, no differences). As I said the pagecache eats all memory even with swapping turned off. What is happening? How to avoid this?

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  • Bindable richTextBox still hanging in memory {WPF, Caliburn.Micro}

    - by Paul
    Hi, I use in WFP Caliburn.Micro Framework. I need bindable richTextbox for Document property. I found many ways how do it bindable richTextBox. But I have one problem. From parent window I open child window. Child window consist bindable richTextBox user control. After I close child window and use memory profiler view class with bindabelrichTextBox control and view model class is still hanging in memory. - this cause memory leaks. If I use richTextBox from .NET Framework or richTextBox from Extended WPF Toolkit it doesn’t cause this memory leak problem. I can’t identified problem in bindable richTextBox class. Here is ist class for bindable richTextBox: Base class can be from .NET or Extended toolkit. /// <summary> /// Represents a bindable rich editing control which operates on System.Windows.Documents.FlowDocument /// objects. /// </summary> public class BindableRichTextBox : RichTextBox { /// <summary> /// Identifies the <see cref="Document"/> dependency property. /// </summary> public static readonly DependencyProperty DocumentProperty = DependencyProperty.Register("Document", typeof(FlowDocument), typeof(BindableRichTextBox)); /// <summary> /// Initializes a new instance of the <see cref="BindableRichTextBox"/> class. /// </summary> public BindableRichTextBox() : base() { } /// <summary> /// Initializes a new instance of the <see cref="BindableRichTextBox"/> class. /// </summary> /// <param title="document">A <see cref="T:System.Windows.Documents.FlowDocument"></see> to be added as the initial contents of the new <see cref="T:System.Windows.Controls.BindableRichTextBox"></see>.</param> public BindableRichTextBox(FlowDocument document) : base(document) { } /// <summary> /// Raises the <see cref="E:System.Windows.FrameworkElement.Initialized"></see> event. This method is invoked whenever <see cref="P:System.Windows.FrameworkElement.IsInitialized"></see> is set to true internally. /// </summary> /// <param title="e">The <see cref="T:System.Windows.RoutedEventArgs"></see> that contains the event data.</param> protected override void OnInitialized(EventArgs e) { // Hook up to get notified when DocumentProperty changes. DependencyPropertyDescriptor descriptor = DependencyPropertyDescriptor.FromProperty(DocumentProperty, typeof(BindableRichTextBox)); descriptor.AddValueChanged(this, delegate { // If the underlying value of the dependency property changes, // update the underlying document, also. base.Document = (FlowDocument)GetValue(DocumentProperty); }); // By default, we support updates to the source when focus is lost (or, if the LostFocus // trigger is specified explicity. We don't support the PropertyChanged trigger right now. this.LostFocus += new RoutedEventHandler(BindableRichTextBox_LostFocus); base.OnInitialized(e); } /// <summary> /// Handles the LostFocus event of the BindableRichTextBox control. /// </summary> /// <param title="sender">The source of the event.</param> /// <param title="e">The <see cref="System.Windows.RoutedEventArgs"/> instance containing the event data.</param> void BindableRichTextBox_LostFocus(object sender, RoutedEventArgs e) { // If we have a binding that is set for LostFocus or Default (which we are specifying as default) // then update the source. Binding binding = BindingOperations.GetBinding(this, DocumentProperty); if (binding.UpdateSourceTrigger == UpdateSourceTrigger.Default || binding.UpdateSourceTrigger == UpdateSourceTrigger.LostFocus) { BindingOperations.GetBindingExpression(this, DocumentProperty).UpdateSource(); } } /// <summary> /// Gets or sets the <see cref="T:System.Windows.Documents.FlowDocument"></see> that represents the contents of the <see cref="T:System.Windows.Controls.BindableRichTextBox"></see>. /// </summary> /// <value></value> /// <returns>A <see cref="T:System.Windows.Documents.FlowDocument"></see> object that represents the contents of the <see cref="T:System.Windows.Controls.BindableRichTextBox"></see>.By default, this property is set to an empty <see cref="T:System.Windows.Documents.FlowDocument"></see>. Specifically, the empty <see cref="T:System.Windows.Documents.FlowDocument"></see> contains a single <see cref="T:System.Windows.Documents.Paragraph"></see>, which contains a single <see cref="T:System.Windows.Documents.Run"></see> which contains no text.</returns> /// <exception cref="T:System.ArgumentException">Raised if an attempt is made to set this property to a <see cref="T:System.Windows.Documents.FlowDocument"></see> that represents the contents of another <see cref="T:System.Windows.Controls.RichTextBox"></see>.</exception> /// <exception cref="T:System.ArgumentNullException">Raised if an attempt is made to set this property to null.</exception> /// <exception cref="T:System.InvalidOperationException">Raised if this property is set while a change block has been activated.</exception> public new FlowDocument Document { get { return (FlowDocument)GetValue(DocumentProperty); } set { SetValue(DocumentProperty, value); } } } Thank fro help and advice. Qucik example: Child window with .NET richTextBox <Window x:Class="WpfApplication2.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="Window1" Height="300" Width="300"> <Grid> <RichTextBox Background="Green" VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto" FontSize="13" Margin="4,4,4,4" Grid.Row="0"/> </Grid> </Window> This window I open from parent window: var w = new Window1(); w.Show(); Then close this window, check with memory profiler and it memory doesn’t exist any object of window1 - richTextBox. It’s Ok. But then I try bindable richTextBox: Child window 2: <Window x:Class="WpfApplication2.Window2" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:Controls="clr-namespace:WpfApplication2.Controls" Title="Window2" Height="300" Width="300"> <Grid> <Controls:BindableRichTextBox Background="Red" VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto" FontSize="13" Margin="4,4,4,4" Grid.Row="0" /> </Grid> </Window> Open child window 2, close this child window and in memory are still alive object of this child window also bindable richTextBox object.

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