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  • Naive question of memory references in Operating system

    - by darkie15
    Hi All, I am learning memory references pertaining to Operating systems and don't seem to get to the crux of understanding it. For example, I am not able to visualize this scenario properly: "A 36 bit address employs both paging and segmentation. Both PTE and STE are 4 bytes each". How are they related? I can guess that this question might be too simple for many. But any help understanding the above basic concept would be appreciable. Regards, darkie15

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  • Basic shared memory program in C

    - by nicopuri
    Hi, I want to make a basic chat application in C using Shared memory. I am working in Linux. The application consist in writing the client and the server can read, and if the server write the client can read the message. I tried to do this, but I can't achieve the communication between client and server. The code is the following: Server.c int main(int argc, char **argv) { char *msg; static char buf[SIZE]; int n; msg = getmem(); memset(msg, 0, SIZE); initmutex(); while ( true ) { if( (n = read(0, buf, sizeof buf)) 0 ) { enter(); sprintf(msg, "%.*s", n, buf); printf("Servidor escribe: %s", msg); leave(); }else{ enter(); if ( strcmp(buf, msg) ) { printf("Servidor lee: %s", msg); strcpy(buf, msg); } leave(); sleep(1); } } return 0; } Client.c int main(int argc, char **argv) { char *msg; static char buf[SIZE-1]; int n; msg = getmem(); initmutex(); while(true) { if ( (n = read(0, buf, sizeof buf)) 0 ) { enter(); sprintf(msg, "%.*s", n, buf); printf("Cliente escribe: %s", msg); leave(); }else{ enter(); if ( strcmp(buf, msg) ) { printf("Cliente lee: %s", msg); strcpy(buf, msg); } leave(); sleep(1); } } printf("Cliente termina\n"); return 0; } The shared memory module is the folowing: #include "common.h" void fatal(char *s) { perror(s); exit(1); } char * getmem(void) { int fd; char *mem; if ( (fd = shm_open("/message", O_RDWR|O_CREAT, 0666)) == -1 ) fatal("sh_open"); ftruncate(fd, SIZE); if ( !(mem = mmap(NULL, SIZE, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0)) ) fatal("mmap"); close(fd); return mem; } static sem_t *sd; void initmutex(void) { if ( !(sd = sem_open("/mutex", O_RDWR|O_CREAT, 0666, 1)) ) fatal("sem_open"); } void enter(void) { sem_wait(sd); } void leave(void) { sem_post(sd); }

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  • sql server 2008 takes alot of memory?

    - by Ahmed Said
    I making stress test on my database which is hosted on sqlserver 2008 64bit running on 64bit machine 10 GB of RAM. I have 400 threads each thread query the database for every second but the query time does not take time as the sql profiler says that, but after 18 hours sql takes 7.2 GB RAM and 7.2 on virtual memroy. Does is this normal behavior? and how can I adjust sql to clean up not in use memory?

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  • memory usage by objects in common lisp

    - by Farzad Bekran
    Is there a way to find out how much memory is used by an instance of a class or basic data types in general? I have a toy webframework in cl that creates and manages web pages with instances of classes that represent the html tags and their properties, and as they are supposed to make an html page, they have children in a slot called children. so I was thinking how much a user's session will cost the server if I take this approach. Thanks.

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  • If I allocate memory in one thread in C++ can I de-allocate it in another

    - by Shane MacLaughlin
    If I allocate memory in one thread in C++ (either new or malloc) can I de-allocate it in another, or must both occur in the same thread? Ideally, I'd like to avoid this in the first place, but I'm curious to know is it legal, illegal or implementation dependent. Edit: The compilers I'm currently using include VS2003, VS2008 and Embedded C++ 4.0, targetting XP, Vista, Windows 7 and various flavours of Windows CE / PocketPC & Mobile. So basically all Microsoft but across an array of esoteric platforms.

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  • Why do I have a memory leak in UIApplication

    - by saintmac
    I have an iphone app project. I analysed it using instruments memory leak tool. According to instruments I have 2 leaks the Trace is as follows: start main UIAplicationMain _run CFRunLoopInMode CFRunLoopRunSpecific PurpleEventCallback _UIAplicationHandleEvent sendEvent: handleEvent:withNewEvent: After this trace there are two separate traces. What causes this and how can I fix it?

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  • Memory randomization as application security enhancement?

    - by Paul Sasik
    I recently came upon a Microsoft article that touted new "defensive enhancements" of Windows 7. Specifically: Address space layout randomization (ASLR) Heap randomization Stack randomization The article went on to say that "...some of these defenses are in the core operating system, and the Microsoft Visual C++ compiler offers others" but didn't explain how these strategies would actually increase security. Anyone know why memory randomization increases security, if at all? Do other platforms and compilers employ similar strategies?

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  • Searching a process' memory on Linux

    - by Matt Joiner
    How can I search the memory state of an process in Linux? Specifically I wish to identify certain regions of interest, and peek at them at regular intervals, possibly occasionally poking new values. I suspect an answer may involve calls to ptrace(), and reading /proc/[pid]/mem, but need more to go on.

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  • Dump to CSV/Postgres memory

    - by alex
    I have a large table (300 million lines) that I would like to dump to a csv - I need to do some processing that cannot be done with SQL. Right now I am using Squirrel as a client, and it does not apparently deal very well with large datasets - at least as far as I can tell from my own (limited) experience. If I run the query on the actual host, will it use less memory? Thanks for any help.

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  • Visual Studio Memory Hog

    - by gentoo_drummer
    I have installed Visual Studio Express Web Developer 2010 and boy it really slows my system down a lot. Is there a way to identify the services like SQL Server and set them to manual so I can avoid all my memory resources been occupied when not using Visual Studio? Is it just SQL Express the problem or are there any other things I should consider disabling in order to have a fast and reliable system when not using Visual Studio? Thanks!

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  • Java Thread - Memory consistency errors

    - by Yatendra Goel
    I was reading a Sun's tutorial on Concurrency. But I couldn't understand exactly what memory consistency errors are? I googled about that but didn't find any helpful tutorial or article about that. I know that this question is a subjective one, so you can provide me links to articles on the above topic. It would be great if you explain it with a simple example.

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  • iPhone memory management, a newbie question

    - by Reuven
    Hi, I've seen in (Apple) sample code two types of ways of allocation memory, and am not sure I understand the difference and resulting behavior. // FAILS NSMutableArray *anArray = [NSMutableArray array]; [anArray release]; // WORKS NSMutableArray *anArray1 = [[NSMutableArray alloc] init]; [anArray release]; By "FAILS" I mean I get crashes/runtime warnings etc., and not always as soon as I call the release... Any explanation appreciated. Thanks

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  • CoreData leak when reading a property

    - by Kamchatka
    Hello, I have the following code in a loop iterating over the different document objects: NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init]; [document primitiveValueForKey:@"data"]; [data writeToFile:filename atomically:NO]; [document.managedObjectContext refreshObject:document mergeChanges:NO]; [pool release]; The "data" property is a large blob (a 1MB image). And as I monitor the memory with the Allocation Instrument memory usage is increasing. I cannot find where the leak is coming from and how to remove it. Thanks!

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  • Class destructor memory handling in C++

    - by wyatt
    What potential memory leaks won't an implicit destructor handle? I know that if you have anything stored on the heap it won't handle it, and if you have a connection to a file or a database, that needs to be handled manually. Is there anything else? What about, say, non-base data types like vectors? Also, in an explicit destructor, need you destroy non-heap variables which would have been destroyed by the implicit, or are they handled automatically? Thanks

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  • Why exactly is calling the destructor for the second time undefined behavior in C++?

    - by sharptooth
    As mentioned in this answer simply calling the destructor for the second time is already undefined behavior 12.4/14(3.8). For example: class Class { public: ~Class() {} }; // somewhere in code: { Class* object = new Class(); object->~Class(); delete object; // UB because at this point the destructor call is attempted again } In this example the class is designed in such a way that the destructor could be called multiple times - no things like double-deletion can happen. The memory is still allocated at the point where delete is called - the first destructor call doesn't call the ::operator delete() to release memory. For example, in Visual C++ 9 the above code looks working. Even C++ definition of UB doesn't directly prohibit things qualified as UB from working. So for the code above to break some implementation and/or platform specifics are required. Why exactly would the above code break and under what conditions?

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  • Pointers in For loops

    - by Bobby
    Quick question: I am a C# guy debugging a C++ app so I am not used to memory management. In the following code: for(int i = 0; i < TlmMsgDB.CMTGetTelemMsgDBCount(); i++) { CMTTelemetryMsgCls* telm = TlmMsgDB.CMTGetTelemetryMsg(i); CMT_SINT32_Tdef id = telm->CMTGetPackingMapID(); ManualScheduleTables.SetManualMsg(i,id); ManualScheduleTables.SetManExec(i,false); } Am I leaking memory every iteration b/c of CMTTelemetryMsgCls* telm = TlmMsgDB.CMTGetTelemetryMsg(i);? The "CMTGetTelemetryMsg(int)" method returns a pointer. Do I have to "delete telm;" at the end of each iteration?

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  • Ruby: execute a binary file in memory?

    - by John
    Is it possible to read binary in ruby file and execute it directly in memory? for example something like this: x = IO.read('/bin/ls') execute(x) I tried system(x) but it doesn't work ArgumentError: string contains null byte

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  • sqlite eatingup memory on iPhone when doing insert

    - by kviksilver
    I am having problem with inserting data to sqlite database. char *update="INSERT OR REPLACE INTO ct_subject (id,id_parent, title, description, link, address, phone, pos_lat, pos_long, no_votes, avg_vote, photo, id_comerc, id_city, placement, type, timestamp, mail) VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?);"; sqlite3_stmt *stmt; if(sqlite3_prepare_v2(database, update, -1, &stmt, nil) == SQLITE_OK){ sqlite3_bind_int(stmt, 1, [[[newCategories objectAtIndex:i] valueForKey:@"id"] intValue]); sqlite3_bind_int(stmt, 2, [[[newCategories objectAtIndex:i] valueForKey:@"id_parent"] intValue]); sqlite3_bind_text(stmt, 3, [[[newCategories objectAtIndex:i] valueForKey:@"title"] UTF8String], -1, NULL); sqlite3_bind_text(stmt, 4, [[[newCategories objectAtIndex:i] valueForKey:@"description"] UTF8String], -1, NULL); sqlite3_bind_text(stmt, 5, [[[newCategories objectAtIndex:i] valueForKey:@"link"] UTF8String], -1, NULL); sqlite3_bind_text(stmt, 6, [[[newCategories objectAtIndex:i] valueForKey:@"address"] UTF8String], -1, NULL); sqlite3_bind_text(stmt, 7, [[[newCategories objectAtIndex:i] valueForKey:@"phone"] UTF8String], -1, NULL); sqlite3_bind_text(stmt, 8, [[[newCategories objectAtIndex:i] valueForKey:@"pos_lat"] UTF8String], -1, NULL); sqlite3_bind_text(stmt, 9, [[[newCategories objectAtIndex:i] valueForKey:@"pos_long"] UTF8String], -1, NULL); sqlite3_bind_int(stmt, 10, [[[newCategories objectAtIndex:i] valueForKey:@"no_votes"] intValue]); sqlite3_bind_text(stmt, 11, [[[newCategories objectAtIndex:i] valueForKey:@"avg_vote"] UTF8String], -1, NULL); if ([[[newCategories objectAtIndex:i] valueForKey:@"photo"] length]!=0) { NSMutableString *webUrl = (NSMutableString *)[[NSMutableString alloc] initWithString:@"http://www.crotune.com/public/images/subjects/"]; [webUrl appendString:[[newCategories objectAtIndex:i] valueForKey:@"photo"]]; UIImage *myImage = [self getWebImage:webUrl]; if(myImage != nil){ sqlite3_bind_blob(stmt, 12, [UIImagePNGRepresentation(myImage) bytes], [UIImagePNGRepresentation(myImage) length], NULL); } else { sqlite3_bind_blob(stmt, 12, nil, -1, NULL); } [webUrl release]; [myImage release]; } else { sqlite3_bind_blob(stmt, 12, nil, -1, NULL); //NSLog(@" ne dodajem sliku2"); } sqlite3_bind_int(stmt, 13, [[[newCategories objectAtIndex:i] valueForKey:@"id_comerc"] intValue]); sqlite3_bind_int(stmt, 14, [[[newCategories objectAtIndex:i] valueForKey:@"id_city"] intValue]); sqlite3_bind_int(stmt, 15, [[[newCategories objectAtIndex:i] valueForKey:@"placement"] intValue]); sqlite3_bind_int(stmt, 16, [[[newCategories objectAtIndex:i] valueForKey:@"type"] intValue]); sqlite3_bind_int(stmt, 17, [[[newCategories objectAtIndex:i] valueForKey:@"timestamp"] intValue]); sqlite3_bind_text(stmt, 18, [[[newCategories objectAtIndex:i] valueForKey:@"mail"] UTF8String], -1, NULL); } if (sqlite3_step(stmt) != SQLITE_DONE) { NSLog(@"%s", sqlite3_errmsg(database)); NSAssert1(0,@"nemogu updateat table %s", errorMsg); } else { NSLog(@"Ubacio %d",i); }sqlite3_finalize(stmt); What happens is that it starts to eat memory until it finaly quits... On memory warning i close and open database again, I have set cache size to 50 as mentioned in some posts here, and tried putting query into statement - same result.. it just garbles mamory and app quits after 300 inserts on iphone or somewhere around 900 inserts on iPad... Any help would be appreciated..

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