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• Protecting an Application's Memory From Tampering

  - by Changeling

  We are adding AES 256 bit encryption to our server and client applications for encrypting the TCP/IP traffic containing sensitive information. We will be rotating the keys daily. Because of that, the keys will be stored in memory with the applications. Key distribution process: Each server and client will have a list of initial Key Encryption Key's (KEK) by day If the client has just started up or the server has just started up, the client will request the daily key from the server using the initial key. The server will respond with the daily key, encrypted with the initial key. The daily key is a randomly generated set of alphanumeric characters. We are using AES 256 bit encryption. All subsequent communications will be encrypted using that daily key. Nightly, the client will request the new daily key from the server using the current daily key as the current KEK. After the client gets the new key, the new daily key will replace the old daily key. Is it possible for another bad application to gain access to this memory illegally or is this protected in Windows? The key will not be written to a file, only stored in a variable in memory. If an application can access the memory illegally, how can you protect the memory from tampering? We are using C++ and XP (Vista/7 may be an option in the future so I don't know if that changes the answer).

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• Memory Warning but Small Live Bytes

  - by Kamchatka

  Hi everyone, In my application, I get a memory warning of level 1 and then 2 after repeating some action (choosing a picture + processing) several times and then a crash. The leak tool doesn't show any leak. I'm also following the Allocations tool in Instruments and my Live Bytes are roughly 4 MB, overall I allocate 113 MB. At maximum I have maybe 20 MB in memory when the picture is loaded. Since I have to repeat an action to get to the crash, it is very likely to be a memory leak. However, I don't know how to locate it since my live bytes are 4 MB and things supposed to be allocated (apart a small leak of ~100 KB in the UIImagePickerController). How much can I trust the memory leak/allocation tools? Would you have an advice to help me locate the reason of the problem?

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• C++ vtable resolving with virtual inheritance

  - by Tomas Cokis

  I was curious about C++ and virtual inheritance - in particular, the way that vtable conflicts are resolved between bass and child classes. I won't pretend to understand the specifics on how they work, but what I've gleamed so far is that their is a small delay caused by using virtual functions due to that resolution. My question then is if the base class is blank - ie, its virtual functions are defined as: virtual void doStuff() = 0; Does this mean that the resolution is not necessary, because there's only one set of functions to pick from? Forgive me if this is an stupid question - as I said, I don't understand how vtables work so I don't really know any better.

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• Objective-c for the iphone: Mystery memory leak

  - by user200341

  My application seems to have 4 memory leaks (on the device, running instruments). The memory leaks seems to come from this code: NSURL *url = [self getUrl:destination]; [destination release]; NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url]; [url release]; [request setHTTPMethod:@"GET"]; [request addValue:@"application/json" forHTTPHeaderField:@"content-type"]; NSURLConnection *connection = [[NSURLConnection alloc]initWithRequest:request delegate:self]; [request release]; [connection release]; I am releasing all my objects as far as I can see but it's still showing this as the source of the 4 memory leaks. This is on the Device running 3.1.3 Is it acceptable to have a few memory leaks in your app or do they all have to go?

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• C# performance varying due to memory

  - by user1107474

  Hope this is a valid post here, its a combination of C# issues and hardware. I am benchmarking our server because we have found problems with the performance of our quant library (written in C#). I have simulated the same performance issues with some simple C# code- performing very heavy memory-usage. The code below is in a function which is spawned from a threadpool, up to a maximum of 32 threads (because our server has 4x CPUs x 8 cores each). This is all on .Net 3.5 The problem is that we are getting wildly differing performance. I run the below function 1000 times. The average time taken for the code to run could be, say, 3.5s, but the fastest will only be 1.2s and the slowest will be 7s- for the exact same function! I have graphed the memory usage against the timings and there doesnt appear to be any correlation with the GC kicking in. One thing I did notice is that when running in a single thread the timings are identical and there is no wild deviation. I have also tested CPU-bound algorithms and the timings are identical too. This has made us wonder if the memory bus just cannot cope. I was wondering could this be another .net or C# problem, or is it something related to our hardware? Would this be the same experience if I had used C++, or Java?? We are using 4x Intel x7550 with 32GB ram. Is there any way around this problem in general? Stopwatch watch = new Stopwatch(); watch.Start(); List<byte> list1 = new List<byte>(); List<byte> list2 = new List<byte>(); List<byte> list3 = new List<byte>(); int Size1 = 10000000; int Size2 = 2 * Size1; int Size3 = Size1; for (int i = 0; i < Size1; i++) { list1.Add(57); } for (int i = 0; i < Size2; i = i + 2) { list2.Add(56); } for (int i = 0; i < Size3; i++) { byte temp = list1.ElementAt(i); byte temp2 = list2.ElementAt(i); list3.Add(temp); list2[i] = temp; list1[i] = temp2; } watch.Stop(); (the code is just meant to stress out the memory) I would include the threadpool code, but we used a non-standard threadpool library. EDIT: I have reduced "size1" to 100000, which basically doesn't use much memory and I still get a lot of jitter. This suggests it's not the amount of memory being transferred, but the frequency of memory grabs?

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• Ways to avoid Memory Leaks in C/C++

  - by Ankur

  What are some tips I can use to avoid memory leaks in my applications? In my current project I use a tool "INSURE++" which finds the memory leak and generate the report. Apart from the tool is there any method to identify memory leaks and overcome it.

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• c# : simulate memory leaks..

  - by dotnet-practitioner

  Hi, I would like to write the following code in c#. a) small console application that simulates memory leak. b) small console application that would invoke the above application and release it right away simulating managing memory leak problem.. In other words the (b) application would continuously call and release application (a) to simulate how the "rebellious" memory leak application is being contained with out addressing the root cause which is application (a). Some sample code for application (a) and (b) would be very helpful. Thanks

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• Emgu CV - memory-leaks (memory consumption)

  - by martin pilch

  I am using EmguCV, the OpenCV wrapper for .NET. I am disposing all created objects but my app is still using more and more memory (in release configuration too). I have debugged my app using .NET Memory profiler and get this result: http://img532.imageshack.us/img532/2503/screenqv.png all objects instance count is oscilating but GChandle instance counr is increasing until my machine is unusable. Garbage collector does not release memory (i think). I am using VS 2008 professional, Win7 prof 32-bit, both up to date, and last stable version of emguCV. I can post some app code, if it will help. Thanks and sorry for my English. Martin

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• Why does my Delphi program's memory continue to grow?

  - by lkessler

  I am using Delphi 2009 which has the FastMM4 memory manager built into it. My program reads in and processes a large dataset. All memory is freed correctly whenever I clear the dataset or exit the program. It has no memory leaks at all. Using the CurrentMemoryUsage routine given in spenwarr's answer to: http://stackoverflow.com/questions/437683/how-to-get-the-memory-used-by-a-delphi-program, I have displayed the memory used by FastMM4 during processing. What seems to be happening is that memory is use is growing after every process and release cycle. e.g.: 1,456 KB used after starting my program with no dataset. 218,455 KB used after loading a large dataset. 71,994 KB after clearing the dataset completely. If I exit at this point (or any point in my example), no memory leaks are reported. 271,905 KB used after loading the same dataset again. 125,443 KB after clearing the dataset completely. 325,519 KB used after loading the same dataset again. 179,059 KB after clearing the dataset completely. 378,752 KB used after loading the same dataset again. It seems that my program's memory use is growing by about 53,400 KB upon each load/clear cycle. Task Manager confirms that this is actually happening. I have heard that FastMM4 does not always release all of the program's memory back to the Operating system when objects are freed so that it can keep some memory around when it needs more. But this continual growing bothers me. Since no memory leaks are reported, I can't identify a problem. Does anyone know why this is happening, if it is bad, and if there is anything I can or should do about it?

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• Use a Free Utility to Create Multiple Virtual Desktops in Windows

  - by Lori Kaufman

  If you’ve used Linux, you’re probably familiar with the virtual desktop feature. It provides a convenient way to organize programs and folders open on your desktop. You can switch among multiple desktops and have different programs and folders open on each one. However, virtual desktops is a feature missing in Windows. There are many third-party options for adding virtual desktops to Windows, including one called Dexpot, which we have covered previously. Dexpot is free, but only for private use. Companies, public institutions, non-profit organizations, and even freelancers and self-employed people must buy the program. We found another virtual desktop tool that is completely free for everyone to use, called mDesktop. It’s a lightweight, open source program that allows you to switch among multiple desktops using hot keys and specify open programs or folders to be active on all desktops. You can use mDesktop to group related programs or to work on different projects on separate desktops. mDesktop is portable and does not need to be installed. Simply extract the .zip file you downloaded (see the link at the end of this article) and double-click the mDesktop.exe file. How To Boot Your Android Phone or Tablet Into Safe Mode HTG Explains: Does Your Android Phone Need an Antivirus? How To Use USB Drives With the Nexus 7 and Other Android Devices

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• Windows Physical Direct Memory Mapping

  - by chrisjleaf

  I'm a bit disappointed there is almost no discussion of this no matter where I look so I guess I'll have to ask. I'm writing a cross platform memory bench marking application which requires direct physical address mapping rather than virtual addressing. EDIT The solution would look something like the Linux/Unix system calls: int fd = open("/dev/mem", O_RDONLY); mmap(NULL, len, PROT_READ, MAP_SHARED, fd, PHYSICAL_ADDRESS_OFFSET); which will require the kernel to either give you a virtual page mapping to the desired physical address or return that it failed. This does require supervisor privileges but that is ok. I have seen a lot of information about shared memory and memory mapped files but all of these reside on disc and are thus not really useful when I'm trying to make a system dependent read. It is very similar to writing an IO driver although I do no need write permissions to the physical address. This site gives an example of how to do it on a driver level using the Windows Driver Kit: NT Insider: Sharing Memory between drivers and applications This solution would probably require Visual Studio which currently I do not have access to. (I have downloaded the WDK api but it complained about my use of GCC for Windows). I'm traditionally a Linux programmer so I'm hoping there might be something really simple I'm missing. Thanks in advance if you know something I don't!

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• How can I fix my Virtual PC 2007 network configuration

  - by DanJ

  Hi, I have installed Windows Virtual PC 2007 on my Windows 2003 R2 Server. I have installed a virtual Windows XP. I have configured the virtual PC to use Shared Networking (NAT) I have disabled the firewall on the virtual windows XP The problem: I am unable to PING from Windows 2003 (the host) to the Windows XP (virtual) I do have normal traffic from the virtual to the internet Could this problem be related to routing? How I can I fix this network configuration to allow for the following traffic: 1. From Virtual to Internet 2. From Host to Virtual 3. If possible, from Internet to Virtual on pre-defined ports (port forwarding?) Thanks

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• G++ Multi-platform memory leak detection tool

  - by indyK1ng

  Does anyone know where I can find a memory memory leak detection tool for C++ which can be either run in a command line or as an Eclipse plug-in in Windows and Linux. I would like it to be easy to use. Preferably one that doesn't overwrite new(), delete(), malloc() or free(). Something like GDB if its gonna be in the command line, but I don't remember that being used for detecting memory leaks. If there is a unit testing framework which does this automatically, that would be great. This question is similar to other questions (such as http://stackoverflow.com/questions/283726/memory-leak-detection-under-windows-for-gnu-c-c ) however I feel it is different because those ask for windows specific solutions or have solutions which I would rather avoid. I feel I am looking for something a bit more specific here. Suggestions don't have to fulfill all requirements, but as many as possible would be nice. Thanks. EDIT: Since this has come up, by "overwrite" I mean anything which requires me to #include a library or which otherwise changes how C++ compiles my code, if it does this at run time so that running the code in a different environment won't affect anything that would be great. Also, unfortunately, I don't have a Mac, so any suggestions for that are unhelpful, but thank you for trying. My desktop runs Windows (I have Linux installed but my dual monitors don't work with it) and I'd rather not run Linux in a VM, although that is certainly an option. My laptop runs Linux, so I can use that tool on there, although I would definitely prefer sticking to my desktop as the screen space is excellent for keeping all of the design documentation and requirements in view without having to move too much around on the desktop. NOTE: While I may try answers, I won't mark one as accepted until I have tried the suggestion and it is satisfactory. EDIT2: I'm not worried about the cross-platform compatibility of my code, it's a command line application using just the C++ libraries.

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• How is an array stored in memory?

  - by George

  In an interest to delve deeper into how memory is allocated and stored, I have written an application that can scan memory address space, find a value, and write out a new value. I developed a sample application with the end goal to be able to programatically locate my array, and overwrite it with a new sequence of numbers. In this situation, I created a single dimensional array, with 5 elements, e.g. int[] array = new int[] {8,7,6,5,4}; I ran my application and searched for a sequence of the five numbers above. I was looking for any value that fell between 4 and 8, for a total of 5 numbers in a row. Unforuntately, my the sequential numbers in my array matched hundreds of results, as the numbers 4 through 8, in no particular sequence happened to be next to each other, in memory, in many situations. Is there any way to distinguish that a set of numbers within memory, represents an array, not simply integers that are next to each other? Is there any way of knowing that if I find a certain value, that the matching values proceeding it are that of an array? I would assume that when I declare int[] array, its pointing at the first address of my array, which would provide some kind of meta-data to what existed in the array, e.g. 0x123456789 meta-data, 5 - 32 bit integers 0x123456789 + 32 "8" 0x123456789 + 64 "7" 0x123456789 + 96 "6" 0x123456789 + 128 "5" 0x123456789 + 160 "4" Am I way off base?

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• Firefox consumes too much memory

  - by Vivek

  I have firefox version 11.0 and am running ubuntu 11.10. Firefox takes upto 850MB RAM with only six or seven tabs opened and all the tabs loaded with light weight websites only. I wonder why would a browser consume so much memory. It keeps increasing its memory consumption over time. I have 3GB RAM and most of the times firefox consumes upto 30% of my memory. How do I fix this? EDIT: The output of the command sudo iotop -oPa as asked by @Jippie

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• Using a GoDaddy SSL certificate with Virtualmin (Webmin)

  - by Kevin

  A client of mine decided to go ahead and move from a self-signed certificate to a commercial one ("GoDaddy Standard SSL"). The first service I wanted to move to the commercial SSL cert was Webmin/Usermin... However, upon migrating to the new SSL cert and restarting Webmin, I got the following error: [21/Oct/2012:13:12:47 -0400] Restarting Failed to open SSL cert /etc/webmin/miniserv.cert at /usr/share/webmin/miniserv.pl line 4229. Error: Webmin server did not write new PID file And that's all it says. Here's Webmin's config file (/etc/webmin/miniserv.conf): port=10000 root=/usr/share/webmin mimetypes=/usr/share/webmin/mime.types addtype_cgi=internal/cgi realm=Webmin Server logfile=/var/webmin/miniserv.log errorlog=/var/webmin/miniserv.error pidfile=/var/webmin/miniserv.pid logtime=168 ppath= ssl=0 env_WEBMIN_CONFIG=/etc/webmin env_WEBMIN_VAR=/var/webmin atboot=1 logout=/etc/webmin/logout-flag listen=10000 denyfile=\.pl$ log=1 blockhost_failures=5 blockhost_time=60 syslog=1 session=1 server=MiniServ/1.600 userfile=/etc/webmin/miniserv.users keyfile=/etc/webmin/miniserv.pem passwd_file=/etc/shadow passwd_uindex=0 passwd_pindex=1 passwd_cindex=2 passwd_mindex=4 passwd_mode=0 preroot=virtual-server-theme passdelay=1 sudo=1 sessiononly=/virtual-server/remote.cgi preload=virtual-server=virtual-server/virtual-server-lib-funcs.pl virtual-server=virtual-server/feature-unix.pl virtual-server=virtual-server/feature-dir.pl virtual-server=virtual-server/feature-dns.pl virtual-server=virtual-server/feature-mail.pl virtual-server=virtual-server/feature-web.pl virtual-server=virtual-server/feature-webalizer.pl virtual-server=virtual-server/feature-ssl.pl virtual-server=virtual-server/feature-logrotate.pl virtual-server=virtual-server/feature-mysql.pl virtual-server=virtual-server/feature-postgres.pl virtual-server=virtual-server/feature-ftp.pl virtual-server=virtual-server/feature-spam.pl virtual-server=virtual-server/feature-virus.pl virtual-server=virtual-server/feature-webmin.pl virtual-server=virtual-server/feature-virt.pl virtual-server=virtual-server/feature-virt6.pl anonymous=/virtualmin-mailman/unauthenticated=anonymous premodules=WebminCore logouttimes= extracas=/etc/webmin/miniserv.chain certfile=/etc/webmin/miniserv.cert ssl_redirect=0 Here is a screen shot of the Webmin SSL config screen as well, for what it's worth: http://postimage.org/image/r472go7tf/ Edited Mon Oct 22 10:45:24 CDT 2012: When running the command openssl x509 -noout -text -in /etc/webmin/miniserv.cert as Falcon Momot suggested, I get the following error: unable to load certificate 139760808240800:error:0906D06C:PEM routines:PEM_read_bio:no start line:pem_lib.c:696:Expecting: TRUSTED CERTIFICATE

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• EBS: OPP Out of memory issue...

  - by ashish.shrivastava

  FO Processor is little more hungry for memory compare to other Java process. If XSLT scalable option is not set and the same time your RTF template is not well optimized definitely you are going to hit Out of memory exception while working with large volume of data. If the memory requirement is not too bad, you can set the OOP Heap size using following SQL queries. Check the current OPP JVM Heap size using following SQL query SQL select DEVELOPER_PARAMETERS from FND_CP_SERVICES where SERVICE_ID = (select MANAGER_TYPE from FND_CONCURRENT_QUEUES where CONCURRENT_QUEUE_NAME = 'FNDCPOPP' DEVELOPER_PARAMETERS ----------------------------------------------------- J:oracle.apps.fnd.cp.gsf.GSMServiceController:-mx512m Set the JVM Heap size using following SQL query SQL update FND_CP_SERVICES set DEVELOPER_PARAMETERS = 'J:oracle.apps.fnd.cp.gsf.GSMServiceController:-mx2048m' where SERVICE_ID = (select MANAGER_TYPE from FND_CONCURRENT_QUEUES where CONCURRENT_QUEUE_NAME = 'FNDCPOPP'); SQLCommit; . You need to restart the Concurrent Manager to make it effective. If this does not resolve the issue, You need to optimize RTF template and set the XSLT scalable option true.

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• Getting started with Oracle Database In-Memory Part III - Querying The IM Column Store

  - by Maria Colgan

  In my previous blog posts, I described how to install, enable, and populate the In-Memory column store (IM column store). This weeks post focuses on how data is accessed within the IM column store. Let’s take a simple query “What is the most expensive air-mail order we have received to date?” SELECT Max(lo_ordtotalprice) most_expensive_order FROM lineorderWHERE  lo_shipmode = 5; The LINEORDER table has been populated into the IM column store and since we have no alternative access paths (indexes or views) the execution plan for this query is a full table scan of the LINEORDER table. You will notice that the execution plan has a new set of keywords “IN MEMORY" in the access method description in the Operation column. These keywords indicate that the LINEORDER table has been marked for INMEMORY and we may use the IM column store in this query. What do I mean by “may use”? There are a small number of cases were we won’t use the IM column store even though the object has been marked INMEMORY. This is similar to how the keyword STORAGE is used on Exadata environments. You can confirm that the IM column store was actually used by examining the session level statistics, but more on that later. For now let's focus on how the data is accessed in the IM column store and why it’s faster to access the data in the new column format, for analytical queries, rather than the buffer cache. There are four main reasons why accessing the data in the IM column store is more efficient. 1. Access only the column data needed The IM column store only has to scan two columns – lo_shipmode and lo_ordtotalprice – to execute this query while the traditional row store or buffer cache has to scan all of the columns in each row of the LINEORDER table until it reaches both the lo_shipmode and the lo_ordtotalprice column. 2. Scan and filter data in it's compressed format When data is populated into the IM column it is automatically compressed using a new set of compression algorithms that allow WHERE clause predicates to be applied against the compressed formats. This means the volume of data scanned in the IM column store for our query will be far less than the same query in the buffer cache where it will scan the data in its uncompressed form, which could be 20X larger. 3. Prune out any unnecessary data within each column The fastest read you can execute is the read you don’t do. In the IM column store a further reduction in the amount of data accessed is possible due to the In-Memory Storage Indexes(IM storage indexes) that are automatically created and maintained on each of the columns in the IM column store. IM storage indexes allow data pruning to occur based on the filter predicates supplied in a SQL statement. An IM storage index keeps track of minimum and maximum values for each column in each of the In-Memory Compression Unit (IMCU). In our query the WHERE clause predicate is on the lo_shipmode column. The IM storage index on the lo_shipdate column is examined to determine if our specified column value 5 exist in any IMCU by comparing the value 5 to the minimum and maximum values maintained in the Storage Index. If the value 5 is outside the minimum and maximum range for an IMCU, the scan of that IMCU is avoided. For the IMCUs where the value 5 does fall within the min, max range, an additional level of data pruning is possible via the metadata dictionary created when dictionary-based compression is used on IMCU. The dictionary contains a list of the unique column values within the IMCU. Since we have an equality predicate we can easily determine if 5 is one of the distinct column values or not. The combination of the IM storage index and dictionary based pruning, enables us to only scan the necessary IMCUs. 4. Use SIMD to apply filter predicates For the IMCU that need to be scanned Oracle takes advantage of SIMD vector processing (Single Instruction processing Multiple Data values). Instead of evaluating each entry in the column one at a time, SIMD vector processing allows a set of column values to be evaluated together in a single CPU instruction. The column format used in the IM column store has been specifically designed to maximize the number of column entries that can be loaded into the vector registers on the CPU and evaluated in a single CPU instruction. SIMD vector processing enables the Oracle Database In-Memory to scan billion of rows per second per core versus the millions of rows per second per core scan rate that can be achieved in the buffer cache. I mentioned earlier in this post that in order to confirm the IM column store was used; we need to examine the session level statistics. You can monitor the session level statistics by querying the performance views v$mystat and v$statname. All of the statistics related to the In-Memory Column Store begin with IM. You can see the full list of these statistics by typing: display_name format a30 SELECT display_name FROM v$statname WHERE  display_name LIKE 'IM%'; If we check the session statistics after we execute our query the results would be as follow; SELECT Max(lo_ordtotalprice) most_expensive_order FROM lineorderWHERE lo_shipmode = 5; SELECT display_name FROM v$statname WHERE  display_name IN ('IM scan CUs columns accessed',                        'IM scan segments minmax eligible',                        'IM scan CUs pruned'); As you can see, only 2 IMCUs were accessed during the scan as the majority of the IMCUs (44) in the LINEORDER table were pruned out thanks to the storage index on the lo_shipmode column. In next weeks post I will describe how you can control which queries use the IM column store and which don't. +Maria Colgan

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• Design review for application facing memory issues

  - by Mr Moose

  I apologise in advance for the length of this post, but I want to paint an accurate picture of the problems my app is facing and then pose some questions below; I am trying to address some self inflicted design pain that is now leading to my application crashing due to out of memory errors. An abridged description of the problem domain is as follows; The application takes in a “dataset” that consists of numerous text files containing related data An individual text file within the dataset usually contains approx 20 “headers” that contain metadata about the data it contains. It also contains a large tab delimited section containing data that is related to data in one of the other text files contained within the dataset. The number of columns per file is very variable from 2 to 256+ columns. The original application was written to allow users to load a dataset, map certain columns of each of the files which basically indicating key information on the files to show how they are related as well as identify a few expected column names. Once this is done, a validation process takes place to enforce various rules and ensure that all the relationships between the files are valid. Once that is done, the data is imported into a SQL Server database. The database design is an EAV (Entity-Attribute-Value) model used to cater for the variable columns per file. I know EAV has its detractors, but in this case, I feel it was a reasonable choice given the disparate data and variable number of columns submitted in each dataset. The memory problem Given the fact the combined size of all text files was at most about 5 megs, and in an effort to reduce the database transaction time, it was decided to read ALL the data from files into memory and then perform the following; perform all the validation whilst the data was in memory relate it using an object model Start DB transaction and write the key columns row by row, noting the Id of the written row (all tables in the database utilise identity columns), then the Id of the newly written row is applied to all related data Once all related data had been updated with the key information to which it relates, these records are written using SqlBulkCopy. Due to our EAV model, we essentially have; x columns by y rows to write, where x can by 256+ and rows are often into the tens of thousands. Once all the data is written without error (can take several minutes for large datasets), Commit the transaction. The problem now comes from the fact we are now receiving individual files containing over 30 megs of data. In a dataset, we can receive any number of files. We’ve started seen datasets of around 100 megs coming in and I expect it is only going to get bigger from here on in. With files of this size, data can’t even be read into memory without the app falling over, let alone be validated and imported. I anticipate having to modify large chunks of the code to allow validation to occur by parsing files line by line and am not exactly decided on how to handle the import and transactions. Potential improvements I’ve wondered about using GUIDs to relate the data rather than relying on identity fields. This would allow data to be related prior to writing to the database. This would certainly increase the storage required though. Especially in an EAV design. Would you think this is a reasonable thing to try, or do I simply persist with identity fields (natural keys can’t be trusted to be unique across all submitters). Use of staging tables to get data into the database and only performing the transaction to copy data from staging area to actual destination tables. Questions For systems like this that import large quantities of data, how to you go about keeping transactions small. I’ve kept them as small as possible in the current design, but they are still active for several minutes and write hundreds of thousands of records in one transaction. Is there a better solution? The tab delimited data section is read into a DataTable to be viewed in a grid. I don’t need the full functionality of a DataTable, so I suspect it is overkill. Is there anyway to turn off various features of DataTables to make them more lightweight? Are there any other obvious things you would do in this situation to minimise the memory footprint of the application described above? Thanks for your kind attention.

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• Applications affected by memory performance

  - by robotron

  I'm writing a paper on the topic of applications affected more by memory performance than processor performance. I've got a lot written regarding the gap between the two, however I can't seem to find anything about the applications that might be affected more by memory performance than by processor speed. I suppose these are applications that make a large amount of memory references, but I have no idea what kind of applications would make such large number of references to make it stand out? Perhaps databases? Can you please give me any pointers on how to proceed, some links to papers? I'm really stuck.

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• Wheres my memory going?

  - by Stu2000

  My machine keeps 'freezing' before eventaully logging out with all the programs exiting. This is rather annoying, and I think its because I keep running out of memory. I am not running any custom software, just netbeans, chrome etc. (Stuff I usually run on other ubuntu computers without issue). For some reason my memory usage is through the roof as seen here, but I can't quite figure out why. Here is a screenshot which may be useful with htop and gnome-system monitor open as user and as root. I notice that my console-kit-daemon is taking up about a gig of 'virtual memory'. Is that normal? Any tips/advice will be helpful. In the meantime I have ordered 2 x 4 gig ram sticks to try and just throw hardware at the issue.

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• Loading saved byte array to memory stream causes out of memory exception

  - by user2320861

  At some point in my program the user selects a bitmap to use as the background image of a Panel object. When the user does this, the program immediately draws the panel with the background image and everything works fine. When the user clicks "Save", the following code saves the bitmap to a DataTable object. MyDataSet.MyDataTableRow myDataRow = MyDataSet.MyDataTableRow.NewMyDataTableRow(); //has a byte[] column named BackgroundImageByteArray using (MemoryStream stream = new MemoryStream()) { this.Panel.BackgroundImage.Save(stream, ImageFormat.Bmp); myDataRow.BackgroundImageByteArray = stream.ToArray(); } Everything works fine, there is no out of memory exception with this stream, even though it contains all the image bytes. However, when the application launches and loads saved data, the following code throws an Out of Memory Exception: using (MemoryStream stream = new MemoryStream(myDataRow.BackGroundImageByteArray)) { this.Panel.BackgroundImage = Image.FromStream(stream); } The streams are the same length. I don't understand how one throws an out of memory exception and the other doesn't. How can I load this bitmap? P.S. I've also tried using (MemoryStream stream = new MemoryStream(myDataRow.BackgroundImageByteArray.Length)) { stream.Write(myDataRow.BackgroundImageByteArray, 0, myDataRow.BackgroundImageByteArray.Length); //throw OoM exception here. }

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• Memory allocation in case of static variables

  - by eSKay

  I am always confused about static variables, and the way memory allocation happens for them. For example: int a = 1; const int b = 2; static const int c = 3; int foo(int &arg){ arg++; return arg; } How is the memory allocated for a,b and c? What is the difference (in terms of memory) if I call foo(a), foo(b) and foo(c)?

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• Is there an NSCFTimer memory leak?

  - by mystify

  I tracked down a memory leak with instruments. I always end up with the information that the responsible library is Foundation. When I track that down in my code, I end up here, but there's nothing wrong with my memory management: - (void)setupTimer { // stop timer if still there [self stopAnimationTimer]; NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:0.2 target:self selector:@selector(step:) userInfo:nil repeats:YES]; self.animationTimer = timer; // retain property, -release in -dealloc method } the property animationTimer is retaining the timer. In -dealloc I -release it. Now that looks like a framework bug? I checked with iPhone OS 3.0 and 3.1, both have that problem every time I use NSTimer like this. Any idea what else could be the problem? (my memory leak scan interval was 0.1 seconds. but same thing with 5 seconds)

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• UIWebView memory management

  - by wolfrevo

  Hello, I have a problem with memory management. I am developing an application that makes heavy use of UIWebView. This app generates dynamically lots of UIWebViews while loading content from my server. Some of these UIWebViews are quite large and have a lot of pictures. If I use instruments to detect leaks, I do not detect any. However, lots of objects are allocated and I suspect that has to do with the UIWebViews. When the webviews release because no longer needed, it appears that not all memory is released. I mean, after a request to my server the app creates an UITableView and many webviews (instruments say about 8Mb). When user tap back, all of them are released but memory usage only decrements about 2-3 Mb, and after 5-10 minutes using the app it crashes. Am I missing something? Anyone know what could be happening? Thank you!

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