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• Copying an sqlite database from file to :memory using C#

  - by davidb

  I have a small database with tables containing a small amount of data which I need to copy into memory. Currently I am using: insertcommand.CommandText = "SELECT sql FROM sqlite_master WHERE sql NOT NULL;"; To pull all the table schema from the file database, however I'm not really sure how to proceed with creating these tables in the new memory database, and copying all the relevant data across. In short, how do I copy an SQLite database from file to memory using C# and System.Data.SQLite?

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• How to reliably measure available memory in Linux?

  - by Alex B

  Linux /proc/meminfo shows a number of memory usage statistics. MemTotal: 4040732 kB MemFree: 23160 kB Buffers: 163340 kB Cached: 3707080 kB SwapCached: 0 kB Active: 1129324 kB Inactive: 2762912 kB There is quite a bit of overlap between them. For example, as far as I understand, there can be active page cache (belongs to "cached" and "active") and inactive page cache ("inactive" + "cached"). What I want to do is to measure "free" memory, but in a way that it includes used pages that are likely to be dropped without a significant impact on overall system's performance. At first, I was inclined to use "free" + "inactive", but Linux's "free" utility uses "free" + "cached" in its "buffer-adjusted" display, so I am curious what a better approach is. When the kernel runs out of memory, what is the priority of pages to drop and what is the more appropriate metric to measure available memory?

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• Finding cause of memory leaks in large PHP stacks

  - by Mike B

  I have CLI script that runs over several thousand iterations between runs and it appears to have a memory leak. I'm using a tweaked version of Zend Framework with Smarty for view templating and each iteration uses several MB worth of code. The first run immediately uses nearly 8MB of memory (which is fine) but every following run adds about 80kb. My main loop looks like this (very simplified) $users = UsersModel::getUsers(); foreach($users as $user) { $obj = new doSomethingAwesome(); $obj->run($user); $obj = null; unset($obj); } The point is that everything in scope should be unset and the memory freed. My understanding is that PHP runs through its garbage collection process at it's own desire but it does so at the end of functions/methods/scripts. So something must be leaking memory inside doSomethingAwesome() but as I said it is a huge stack of code. Ideally, I would love to find some sort of tool that displayed all my variables no matter the scope at some point during execution. Some sort of symbol-table viewer for php. Does anything like that or any other tools that could help nail down memory leaks in php exist?

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• Beginner assembly programming memory usage question

  - by Daniel

  I've been getting into some assembly lately and its fun as it challenges everything i have learned. I was wondering if i could ask a few questions When running an executable, does the entire executable get loaded into memory? From a bit of fiddling i've found that constants aren't really constants? Is it just a compiler thing? const int i = 5; _asm { mov i, 0 } // i is now 0 and compiles fine So are all variables assigned with a constant value embedded into the file as well? Meaning: int a = 1; const int b = 2; void something() { const int c = 3; int d = 4; } Will i find all of these variables embedded in the file (in a hex editor or something)? If the executable is loaded into memory then "constants" are technically using memory? I've read around on the net people saying that constants don't use memory, is this true?

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• C vs. C++ for performance in memory allocation

  - by Andrei

  Hi, I am planning to participate in development of a code written in C language for Monte Carlo analysis of complex problems. This codes allocates huge data arrays in memory to speed up its performance, therefore the author of the code has chosen C instead of C++ claiming that one can make faster and more reliable (concerning memory leaks) code with C. Do you agree with that? What would be your choice, if you need to store 4-16 Gb of data arrays in memory during calculation?

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• Memory Allocation for a Map with a fixed number of insertions

  - by prasoon99

  I want to insert n elements into a map where n is known ahead of time. I do not want memory allocation at each insertion. I want all memory allocation at the beginning. Is there a way to do this? If so, how? Will writing some sort of memory allocator help?

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• Reallocating memory via "new" in C++

  - by BSchlinker

  Quick question regarding memory management in C++ If I do the following operation: pointer = new char [strlen(someinput_input)+1]; And then perform it again, with perhaps a different result being returned from strlen(someinput_input). Does this result in memory being left allocated from the previous "new" statement? IE, is each new statement receiving another block of HEAP memory from the OS, or is it simply reallocating? Assuming I do a final delete pointer[]; will that deallocate any and all memory that I ever allocated via new to that pointer? Thanks

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• java memory usage

  - by xdevel2000

  I know I always post a similar question about array memory usage but now I want post the question more specific. After I read this article: http://www.javamex.com/tutorials/memory/object_memory_usage.shtml I didn't understand some things: the size of a data type is always the same also on different platform (Linux / Windows 32 / 64 bit)??? so an int will be always 32 bit?; when I compute the memory usage I must put also the reference value itself? If I have an object to a class that has an int field its memory will be 12 (object header) + 4 reference + 4 (the int field) + 3 (padding) = 24 bytes??

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• Resources for memory management in embedded application

  - by Elazar Leibovich

  How should I manage memory in my mission critical embedded application? I found some articles with google, but couldn't pinpoint a really useful practical guide. The DO-178b forbids dynamic memory allocations, but how will you manage the memory than? preallocate everything in advance and send a pointer to each function that needs allocation? Allocate it on the stack? Use a global static allocator (but then it's very similar to dynamic allocation)? Answers can be of the form of regular answer, reference to a resource, or reference to good opensource embedded system for example. clarification: The issue here is not whether or not memory management is availible for the embedded system. But what is a good design for an embedded system, to maximize reliability.

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• How to keep windows from paging block of memory

  - by photo_tom

  We are working on a Vista/Windows 7 applicaiton that will be running in 64 bit mode using VS2008/C++. We will be needing to cache hundreds of 2-3 mb blobs of data in RAM for performance reasons up to some memory limit. Our usage profile is such that we cannot read the data in fast enough if it is all on the the disk. Cached Memory usage will be larger than 1gb memory used. For this to work well, we need to ensure that Windows does not page this memory out as it will defeat the purpose of why we are doing this. I've done a fair amount of research and cannot find documenation that states exactly how to do this. I've seen several references that infer memory mapped files work this way. Is there an expert who can clarify this for me? I'm aware there are other programs that we could adapt to do this, for example, splitting the blobs and loading into memcache or inmemory databases, but they all have too many problems with performance or code complexity. Suggestions?

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• My iphone app gets memory warning and killed at 6.8MB

  - by Pankaj

  My app has a thread that does some time consuming job for more than a minute and the app consumes around 6.8MB of memory. I receive a memory warning after sometime and then it gets killed. There is nothing that I can release, and I am using not even 7MB of memory...driving me crazy...any advice please?

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• PHP Object Creation and Memory Usage

  - by JohnO

  A basic dummy class: class foo { var $bar = 0; function foo() {} function boo() {} } echo memory_get_usage(); echo "\n"; $foo = new foo(); echo memory_get_usage(); echo "\n"; unset($foo); echo memory_get_usage(); echo "\n"; $foo = null; echo memory_get_usage(); echo "\n"; Outputs: $ php test.php 353672 353792 353792 353792 Now, I know that PHP docs say that memory won't be freed until it is needed (hitting the ceiling). However, I wrote this up as a small test, because I've got a much longer task, using a much bigger object, with many instances of that object. And the memory just climbs, eventually running out and stopping execution. Even though these large objects do take up memory, since I destroy them after I'm done with each one (serially), it should not run out of memory (unless a single object exhausts the entire space for memory, which is not the case). Thoughts?

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• Linux Access physical memory (NOR flash)

  - by Kevin

  Hello, I am trying to access a Linux system's NOR flash memory. I tried use __raw_readl(xxxxx) (through io_p2v) to read NOR memory data, but I failed. Is there any way I can access that memory? Will driver /dev/mem work for this? I guess not. it is only for the RAM maybe. Can anyone help?

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• Techniques for querying a set of object in-memory in a Java application

  - by Edd Grant

  Hi All, We have a system which performs a 'coarse search' by invoking an interface on another system which returns a set of Java objects. Once we have received the search results I need to be able to further filter the resulting Java objects based on certain criteria describing the state of the attributes (e.g. from the initial objects return all objects where x.y z && a.b == c). The criteria used to filter the set of objects each time is partially user configurable, by this I mean that users will be able to select the values and ranges to match on but the attributes they can pick from will be a fixed set. The data sets are likely to contain <= 10,000 objects for each search. The search will be executed manually by the application user base probably no more than 2000 times a day (approx). It's probably worth mentioning that all the objects in the result set are known domain object classes which have Hibernate and JPA annotations describing their structure and relationship. Off the top of my head I can think of 3 ways of doing this: For each search persist the initial result set objects in our database, then use Hibernate to re-query them using the finer grained criteria. Use an in-memory Database (such as hsqldb?) to query and refine the initial result set. Write some custom code which iterates the initial result set and pulls out the desired records. Option 1 seems to involve a lot of toing and froing across a network to a physical Database (Oracle 10g) which might result in a lot of network and disk activity. It would also require the results from each search to be isolated from other result sets to ensure that different searches don't interfere with each other. Option 2 seems like a good idea in principle as it would allow me to do the finer query in memory and would not require the persistence of result data which would only be discarded after the search was complete. Gut feeling is that this could be pretty performant too but might result in larger memory overheads (which is fine as we can be pretty flexible on the amount of memory our JVM gets). Option 3 could be very performant but is something I would like to avoid as any code we write would require such careful testing that the time taken to acheive something flexible and robust enough would probably be prohibitive. I don't have time to prototype all 3 ideas so I am looking for comments people may have on the 3 options above, plus any further ideas I have not considered, to help me decide which idea might be most suitable. I'm currently leaning toward option 2 (in memory database) so would be keen to hear from people with experience of querying POJOs in memory too. Hopefully I have described the situation in enough detail but don't hesitate to ask if any further information is required to better understand the scenario. Cheers, Edd

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• C++ object in memory

  - by Neo_b

  Hello. Is there a standard in storing a C++ objects in memory? I wish to set a char* pointer to a certain address in memory, so that I can read certain objects' variables directly from the memory byte by byte. When I am using Dev C++, the variables are stored one by one right in the memory address of an object in the order that they were defined. Now, can it be different while using a different compiler (like the variables being in a different order, or somewhere else)? Thank you in advance. :-)

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• Effect of suffixes in memory to cache operations

  - by tur1ng

  In x86 GNU Assembler there are different suffixes for memory related operations. E.g.: movb, movs, movw, movl, movq, movt(?) Now my question is the following: Does the suffix has ANY effect on how the processor is getting the data out of main memory or will always be one or more 32-bit (x86) chunks loaded into the cache ? What are the effects beside the memory access?

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• C++ Reserve Memory Space

  - by uray

  is there any way to reserve memory space to be used later by default Windows Memory Manager so that my application won't run out of memory if my program don't use space more than I have reserved at start of my program?

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• iPhone App takes up too much memory

  - by Stephen Furlani

  Ok, so here's my problem. My iPhone app is 1.2MB on disk. Granted I have a bunch of Images for the GUI buttons and backgrounds, etc. In-memory, my app takes up a whopping 15MB! That means if I then take a picture with the camera, 8MB default, it gives a memory warning (several) even before the picker calls its delegate! How can I tell what is grabbing so much memory, and how to remove it? I've removed all of my debugging symbols and added [-Os], but it still takes up a huge amount of memory! Also, (how) can I change the default resolution of the camera?

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• linux: per-process monitor, every 10 minutes, with history access

  - by Inbar Rose

  I really didn't know a better way to ask my question, hence you get a horribly named question. I will explain what i want to do, maybe that will help you help me. I would like to have my linux machine continuously monitor (every 10 minutes) all the processes on my machine. The information from each process that I require is the name, CPU usage, allocated (virtual) memory, and resident (ram) memory. If these periodic reports were to be looked at, they would look something like this: PROCESS CPU RAM VIRTUAL name1 % MB MB name2 % MB MB ...etc..etc These reports should be stored in such a way that I can access them at a later date by giving a date/time scope (range). For instance, if I want to see the history of my processes from 12:00:00 1.12.12 till 12:00:00 2.12.12 I can - and it should give me the history of the processes for every 10 minutes between those date/time borders. The format of the return is not important, that will be handled by a script anyway and can be modified into anything I need. I have looked into a few things so far, but have not found something that clearly meets my needs. Among the things i searched: sar, free(1), top(1).. and a few other things. It should be a simple issue, i can already see all this information by simply looking at my htop, but i need only a tool that will gather the desired fields for me for each processes every 10 minutes, and then also let me extract slices of that data based on date/time scopes (ranges). note: I have limited experience with linux, so please give detailed information. note2: The desired output will be something like this (after receiving the desired range) CPU USAGE BY PROCESS: proc_nameA 1,2,2,2,2,2...... numbers represent % usage every 10 minutes... proc_nameB 4,3,3,6,1,2...... The same idea with the other information.

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• Effect of suffixes in memory operations

  - by tur1ng

  In x86 GNU Assembler there are different suffixes for memory related operations. E.g.: movb, movs, movw, movl, movq, movt(?) Now my question is the following: Does the suffix has ANY effect on how the processor is getting the data out of main memory or will always be one or more 32-bit (x86) chunks loaded into the cache ? What are the effects beside the memory access?

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• Deleting Part of An Array in Java to Free Memory on Heap

  - by kate

  I am implementing a dynamic programming algorithm for the knapsack problem in Java. I declare the array and then initialize its size to be [number of objects][capacity of knapsack]. When my number of objects or my capacity gets too large, I get a memory error because I run out of space on the heap. My questions is: If I delete rows from my double array as I go along, will Java free the memory as I delete? Or does Java reserve that memory space for the size of the array I originally created? If it's the latter, is there a way to manually free the memory in Java? Thanks for your Help!

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• Large number of tables and Hibernate memory consumption

  - by Vedran

  I'm working on a large ERP project which has database model with about 2100 tables. With "only" 500 tables mapped with Hibernate, application deployed on the web server takes about 3GB of working memory. Is there any way to reduce Hibernate's metamodel memory footprint when using that many tables in one persistence unit? Or should I just give up on ORMs and go with plain old JDBC (or even jOOQ)? Right now I'm using Hibernate 4.1.8, Spring 3.1.3, JBoss AS 7.1 and working with MSSQL database. Edit: JavaMelody memory histogram output - with 2000 generated test tables that are a bit smaller in scope from the original db model (hence 'only' 1.3GB of spent memory)

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• Memory allocation patterns in C++

  - by Mahatma

  I am confused about the memory allocation in C++ in terms of the memory areas such as Const data area, Stack, Heap, Freestore, Heap and Global/Static area. I would like to understand the memory allocation pattern in the following snippet. Can anyone help me to understand this. If there any thing more apart from the variable types mentioned in the example to help understand the concept better please alter the example. class FooBar { int n; //Stored in stack? public: int pubVar; //stored in stack? void foo(int param) //param stored in stack { int *pp = new int; //int is allocated on heap. n = param; static int nStat; //Stored in static area of memory int nLoc; //stored in stack? string str = "mystring"; //stored in stack? .. if(CONDITION) { static int nSIf; //stored in static area of memory int loopvar; //stored in stack .. } } } int main(int) { Foobar bar; //bar stored in stack? or a part of it? Foobar *pBar; //pBar is stored in stack pBar = new Foobar(); //the object is created in heap? What part of the object is stored on heap } EDIT: What confuses me is, if pBar = new Foobar(); stores the object on the heap, how come int nLoc; and int pubVar;, that are components of the object stored on stack? Sounds contradictory to me. Shouldn't the lifetime of pubvar and pBar be the same?

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• Access to a process memory

  - by beloc4369

  why do we allocate virtual memory address space within a process to get a read access to its memory?

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• C# accessing memory map file

  - by ooo

  Looking for code samples to access a memory map file in C#

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