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  • Visual C#, Large Arrays, and LOH Fragmentation. What is the accepted convention?

    - by Gorchestopher H
    I have an other active question HERE regarding some hopeless memory issues that possibly involve LOH Fragmentation among possibly other unknowns. What my question now is, what is the accepted way of doing things? If my app needs to be done in Visual C#, and needs to deal with large arrays to the tune of int[4000000], how can I not be doomed by the garbage collector's refusal to deal with the LOH? It would seem that I am forced to make any large arrays global, and never use the word "new" around any of them. So, I'm left with ungraceful global arrays with "maxindex" variables instead of neatly sized arrays that get passed around by functions. I've always been told that this was bad practice. What alternative is there? Is there some kind of function to the tune of System.GC.CollectLOH("Seriously") ? Are there possibly some way to outsource garbage collection to something other than System.GC? Anyway, what are the generally accepted rules for dealing with large (85Kb) variables?

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  • How to free memory in try-catch blocks?

    - by Kra
    Hi, I have a simple question hopefully - how does one free memory which was allocated in the try block when the exception occurs? Consider the following code: try { char *heap = new char [50]; //let exception occur here delete[] heap; } catch (...) { cout << "Error, leaving function now"; //delete[] heap; doesn't work of course, heap is unknown to compiler return 1; } How can I free memory after the heap was allocated and exception occurred before calling delete[] heap? Is there a rule not to allocate memory on heap in these try .. catch blocks? Thanks

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  • SQL Server - Rebuilding Indexes

    - by Renso
    Goal: Rebuild indexes in SQL server. This can be done one at a time or with the example script below to rebuild all index for a specified table or for all tables in a given database. Why? The data in indexes gets fragmented over time. That means that as the index grows, the newly added rows to the index are physically stored in other sections of the allocated database storage space. Kind of like when you load your Christmas shopping into the trunk of your car and it is full you continue to load some on the back seat, in the same way some storage buffer is created for your index but once that runs out the data is then stored in other storage space and your data in your index is no longer stored in contiguous physical pages. To access the index the database manager has to "string together" disparate fragments to create the full-index and create one contiguous set of pages for that index. Defragmentation fixes that. What does the fragmentation affect?Depending of course on how large the table is and how fragmented the data is, can cause SQL Server to perform unnecessary data reads, slowing down SQL Server’s performance.Which index to rebuild?As a rule consider that when reorganize a table's clustered index, all other non-clustered indexes on that same table will automatically be rebuilt. A table can only have one clustered index.How to rebuild all the index for one table:The DBCC DBREINDEX command will not automatically rebuild all of the indexes on a given table in a databaseHow to rebuild all indexes for all tables in a given database:USE [myDB]    -- enter your database name hereDECLARE @tableName varchar(255)DECLARE TableCursor CURSOR FORSELECT table_name FROM information_schema.tablesWHERE table_type = 'base table'OPEN TableCursorFETCH NEXT FROM TableCursor INTO @tableNameWHILE @@FETCH_STATUS = 0BEGINDBCC DBREINDEX(@tableName,' ',90)     --a fill factor of 90%FETCH NEXT FROM TableCursor INTO @tableNameENDCLOSE TableCursorDEALLOCATE TableCursorWhat does this script do?Reindexes all indexes in all tables of the given database. Each index is filled with a fill factor of 90%. While the command DBCC DBREINDEX runs and rebuilds the indexes, that the table becomes unavailable for use by your users temporarily until the rebuild has completed, so don't do this during production  hours as it will create a shared lock on the tables, although it will allow for read-only uncommitted data reads; i.e.e SELECT.What is the fill factor?Is the percentage of space on each index page for storing data when the index is created or rebuilt. It replaces the fill factor when the index was created, becoming the new default for the index and for any other nonclustered indexes rebuilt because a clustered index is rebuilt. When fillfactor is 0, DBCC DBREINDEX uses the fill factor value last specified for the index. This value is stored in the sys.indexes catalog view. If fillfactor is specified, table_name and index_name must be specified. If fillfactor is not specified, the default fill factor, 100, is used.How do I determine the level of fragmentation?Run the DBCC SHOWCONTIG command. However this requires you to specify the ID of both the table and index being. To make it a lot easier by only requiring you to specify the table name and/or index you can run this script:DECLARE@ID int,@IndexID int,@IndexName varchar(128)--Specify the table and index namesSELECT @IndexName = ‘index_name’    --name of the indexSET @ID = OBJECT_ID(‘table_name’)  -- name of the tableSELECT @IndexID = IndIDFROM sysindexesWHERE id = @ID AND name = @IndexName--Show the level of fragmentationDBCC SHOWCONTIG (@id, @IndexID)Here is an example:DBCC SHOWCONTIG scanning 'Tickets' table...Table: 'Tickets' (1829581556); index ID: 1, database ID: 13TABLE level scan performed.- Pages Scanned................................: 915- Extents Scanned..............................: 119- Extent Switches..............................: 281- Avg. Pages per Extent........................: 7.7- Scan Density [Best Count:Actual Count].......: 40.78% [115:282]- Logical Scan Fragmentation ..................: 16.28%- Extent Scan Fragmentation ...................: 99.16%- Avg. Bytes Free per Page.....................: 2457.0- Avg. Page Density (full).....................: 69.64%DBCC execution completed. If DBCC printed error messages, contact your system administrator.What's important here?The Scan Density; Ideally it should be 100%. As time goes by it drops as fragmentation occurs. When the level drops below 75%, you should consider re-indexing.Here are the results of the same table and clustered index after running the script:DBCC SHOWCONTIG scanning 'Tickets' table...Table: 'Tickets' (1829581556); index ID: 1, database ID: 13TABLE level scan performed.- Pages Scanned................................: 692- Extents Scanned..............................: 87- Extent Switches..............................: 86- Avg. Pages per Extent........................: 8.0- Scan Density [Best Count:Actual Count].......: 100.00% [87:87]- Logical Scan Fragmentation ..................: 0.00%- Extent Scan Fragmentation ...................: 22.99%- Avg. Bytes Free per Page.....................: 639.8- Avg. Page Density (full).....................: 92.10%DBCC execution completed. If DBCC printed error messages, contact your system administrator.What's different?The Scan Density has increased from 40.78% to 100%; no fragmentation on the clustered index. Note that since we rebuilt the clustered index, all other index were also rebuilt.

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  • (outofmemoryerror: java heap space) when iterating through oracle records...

    - by rockit
    hello fellow java developers. I'm having a bit of an issue here. I have code that gets a resultset from an oracle database, prints each row to a file, then gets the next row - and continues till the end of the resultset. Only this isn't what happens. What happens is that it gets the resultset, starts iterating through the rows, printing to file as it goes, until it runs out of memory - claiming it needs more space on the java heap. The app is currently running with 2g of memory on the heap and the code breaks at about the 150000th row. I'm using jodbc6.jar and java 6 Here is an idea of what my code is doing: Connection conn = DriverManager.getConnection(url,"name","pwd"); conn.setAutoCommit(false); Statement stmt = conn.createStatement(); ResultSet rset = stmt.executeQuery(strSql); String strVar_1 = null; long lCount = 0; while(rset.next()){ lCount++; if (lCount % 100000 == 0){ System.out.println(lCount + " rows completed"); } strVar_1 = rset.getString("StringID"); /// breaks here!!!!!!!!! if (strVar_1 == null){ strVar_1 = ""; } if (!strQuery_1.equals("")){ out.write(strVar_1 + "\n"); } } out.close();

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  • Does unboxing just return a pointer to the value within the boxed object on the heap?

    - by Charles
    I this MSDN Magazine article, the author states (emphasis mine): Note that boxing always creates a new object and copies the unboxed value's bits to the object. On the other hand, unboxing simply returns a pointer to the data within a boxed object: no memory copy occurs. However, it is commonly the case that your code will cause the data pointed to by the unboxed reference to be copied anyway. I'm confused by the sentence I've bolded and the sentence that follows it. From everything else I've read, including this MSDN page, I've never before heard that unboxing just returns a pointer to the value on the heap. I was under the impression that unboxing would result in you having a variable containing a copy of the value on the stack, just as you began with. After all, if my variable contains "a pointer to the value on the heap", then I haven't got a value type, I've got a pointer. Can someone explain what this means? Was the author on crack? (There is at least one other glaring error in the article). And if this is true, what are the cases where "your code will cause the data pointed to by the unboxed reference to be copied anyway"? I just noticed that the article is nearly 10 years old, so maybe this is something that changed very early on in the life of .Net.

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  • how to solve out of memory error in java in amazon ec2 server

    - by sathishkumar
    can anyone explain about this error message? we are using IBM jre to run java application Its occupying more space on the server. JVMDUMP006I Processing dump event "systhrow", detail "java/lang/OutOfMemoryError" - please wait. JVMDUMP006I Processing dump event "systhrow", detail "java/lang/OutOfMemoryError" - please wait. JVMDUMP032I JVM requested Heap dump using '/home/sathish/jetty6/heapdump.20110417.114115.18926.0001.phd' in response to an event JVMDUMP010I Heap dump written to /home/sathish/jetty6/heapdump.20110417.114115.18926.0001.phd JVMDUMP032I JVM requested Heap dump using '/home/sathish/jetty6/heapdump.20110417.114115.18926.0002.phd' in response to an event JVMDUMP010I Heap dump written to /home/sathish/jetty6/heapdump.20110417.114115.18926.0002.phd JVMDUMP032I JVM requested Heap dump using '/home/sathish/jetty6/heapdump.20110417.114115.18926.0003.phd' in response to an event JVMDUMP010I Heap dump written to /home/sathish/jetty6/heapdump.20110417.114115.18926.0003.phd JVMDUMP032I JVM requested Java dump using '/home/sathish/jetty6/javacore.20110417.114115.18926.0004.txt' in response to an event JVMDUMP010I Java dump written to /home/sathish/jetty6/javacore.20110417.114115.18926.0004.txt

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  • Hi I am facing a fragmentation error while executing this code? Can someone explain why?

    - by aks
    #include<stdio.h> struct table { char *ipAddress; char *domainName; struct table *next; }; struct table *head = NULL; void add_rec(); void show_rec(); int main() { add_rec(); show_rec(); return 0; } void add_rec() { struct table * temp = head; struct table * temp1 = (struct table *)malloc(sizeof(struct table)); if(!temp1) printf("\n Unable to allocate memory \n"); printf("Enter the ip address you want \n"); scanf("%s",temp1->ipAddress); printf("\nEnter the domain name you want \n"); scanf("%s",temp1->domainName); if(!temp) { head = temp; } else { while(temp->next!=NULL) temp = temp->next; temp->next = temp1; } } void show_rec() { struct table * temp = head; if(!temp) printf("\n No entry exists \n"); while(temp!=NULL) { printf("ipAddress = %s\t domainName = %s\n",temp->ipAddress,temp->domainName); temp = temp->next; } } When i execute this code and enters the IP address for the first node, i am facing fragmentation error. The code crashed. Can someone enlighten?

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  • is there stack size in iphone?

    - by senthilmuthu
    Hi, Every RAM must have stack and heap (like CS,ES,DS,SS 4 segments).but is there like stack size in iphone,is only heap available?some tutorial say when we increase stack size , heap will be decreased,when we increase heap size ,stack will be decreased ...is it true..? or fixed stack size or fixed heap size ? any help please?

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  • Spring Web application internal visual monitoring heap space and permgen.

    - by Veniamin
    If I have created web application used Spring framework(based on maven), can I include some module/dependency/plugin into my app to monitor Heap space, Permgen, etc. It whould be greate to get some charts output likes as in VisuaVM. For example: http://localhost:8080/monitoring = Including something likes VisualVM I have found next dependency without link to repo: <dependency> <groupId>com.sun.tools.visualvm</groupId> <artifactId>core</artifactId> <version>1.3.3</version> </dependency> How to use it?

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  • How can I tell what is using the memory when there is a heap overflow in Java?

    - by Grae
    Hi all, I know a little about profiling, but what I am particularlly insterest in, is what has all the memory when I get these heap over flow exceptions. I will start getting them after about a hour of debugging. I am hoping there is some sort of dump or something, that I can use to get a list of what instances are around at the time the program starts. By the way, sorry if this is a lazy question. I really shoud put sometime in learning about profiling. Grae

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  • How to transfer large file (File size > Heap Size) over the network?

    - by neo
    How to transfer large file (File size Heap/RAM Size) over the network ? Lets say I have file (size 10GB) I want to transfer it machine a (RAM 512mb) to machine b (RAM 512mb). Want achieve this using java code. First, is it possible ? Any recommendation on framework. If possible, can we speed this up using threading ? Important criteria: file's data sequence needs to be maintained during transfer. Any example will be great help.

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  • Best Practice: QT4 QList<Mything*>... on Heap, or QList<Mything> using reference?

    - by Mike Crowe
    Hi Folks, Learning C++, so be gentle :)... I have been designing my application primarily using heap variables (coming from C), so I've designed structures like this: QList<Criteria*> _Criteria; // ... Criteria *c = new Criteria(....); _Criteria.append(c); All through my program, I'm passing pointers to specific Criteria, or often the list. So, I have a function declared like this: QList<Criteria*> Decision::addCriteria(int row,QString cname,QString ctype); Criteria * Decision::getCriteria(int row,int col) which inserts a Criteria into a list, and returns the list so my GUI can display it. I'm wondering if I should have used references, somehow. Since I'm always wanting that exact Criteria back, should I have done: QList<Criteria> _Criteria; // .... Criteria c(....); _Criteria.append(c); ... QList<Criteria>& Decision::addCriteria(int row,QString cname,QString ctype); Criteria& Decision::getCriteria(int row,int col) (not sure if the latter line is syntactically correct yet, but you get the drift). All these items are specific, quasi-global items that are the core of my program. So, the question is this: I can certainly allocate/free all my memory w/o an issue in the method I'm using now, but is there are more C++ way? Would references have been a better choice (it's not too late to change on my side). TIA Mike

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  • Escaping an equals sign in DOS batch string replacement command

    - by Alastair
    Hi, I need to replace some text in a JNLP file using a DOS batch file to tune it for the local machine. The problem is that the search pattern contains an equals sign which is messing up the string replacement in the batch file. I want to replace the line, <j2se version="1.5" initial-heap-size="100M" max-heap-size="100M"/> with specific settings for the initial and max heap sizes. For example at the moment I have, for /f "tokens=* delims=" %%a in (%filePath%agility.jnlp) do ( set str=%%a set str=!str:initial-heap-size="100M"=initial-heap-size="%min%M"! echo !str!>>%filePath%new.jnlp) but the = in the search pattern is being read as part of the replacement command. How do I escape the equals sign so it is processed as text?

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  • obiee memory usage

    - by user554629
    Heap memory is a frequent customer topic. Here's the quick refresher, oriented towards AIX, but the principles apply to other unix implementations. 1. 32-bit processes have a maximum addressability of 4GB; usable application heap size of 2-3 GB.  On AIX it is controlled by an environment variable: export LDR_CNTRL=....=MAXDATA=0x080000000   # 2GB ( The leading zero is deliberate, not required )   1a. It is  possible to get 3.25GB  heap size for a 32-bit process using @DSA (Discontiguous Segment Allocation)     export LDR_CNTRL=MAXDATA=0xd0000000@DSA  # 3.25 GB 32-bit only        One side-effect of using AIX segments "c" and "d" is that shared libraries will be loaded privately, and not shared.        If you need the additional heap space, this is worth the trade-off.  This option is frequently used for 32-bit java.   1b. 64-bit processes have no need for the @DSA option. 2. 64-bit processes can double the 32-bit heap size to 4GB using: export LDR_CNTRL=....=MAXDATA=0x100000000  # 1 with 8-zeros    2a. But this setting would place the same memory limitations on obiee as a 32-bit process    2b. The major benefit of 64-bit is to break the binds of 32-bit addressing.  At a minimum, use 8GB export LDR_CNTRL=....=MAXDATA=0x200000000  # 2 with 8-zeros    2c.  Many large customers are providing extra safety to their servers by using 16GB: export LDR_CNTRL=....=MAXDATA=0x400000000  # 4 with 8-zeros There is no performance penalty for providing virtual memory allocations larger than required by the application.  - If the server only uses 2GB of space in 64-bit ... specifying 16GB just provides an upper bound cushion.    When an unexpected user query causes a sudden memory surge, the extra memory keeps the server running. 3.  The next benefit to 64-bit is that you can provide huge thread stack sizes for      strange queries that might otherwise crash the server.      nqsserver uses fast recursive algorithms to traverse complicated control structures.    This means lots of thread space to hold the stack frames.    3a. Stack frames mostly contain register values;  64-bit registers are twice as large as 32-bit          At a minimum you should  quadruple the size of the server stack threads in NQSConfig.INI          when migrating from 32- to 64-bit, to prevent a rogue query from crashing the server.           Allocate more than is normally necessary for safety.    3b. There is no penalty for allocating more stack size than you need ...           it is just virtual memory;   no real resources  are consumed until the extra space is needed.    3c. Increasing thread stack sizes may require the process heap size (MAXDATA) to be increased.          Heap space is used for dynamic memory requests, and for thread stacks.          No performance penalty to run with large heap and thread stack sizes.           In a 32-bit world, this safety would require careful planning to avoid exceeding 2GM usable storage.     3d. Increasing the number of threads also may require additional heap storage.          Most thread stack frames on obiee are allocated when the server is started,          and the real memory usage increases as threads run work. Does 2.8GB sound like a lot of memory for an AIX application server? - I guess it is what you are accustomed to seeing from "grandpa's applications". - One of the primary design goals of obiee is to trade memory for services ( db, query caches, etc) - 2.8GB is still well under the 4GB heap size allocated with MAXDATA=0x100000000 - 2.8GB process size is also possible even on 32-bit Windows applications - It is not unusual to receive a sudden request for 30MB of contiguous storage on obiee.- This is not a memory leak;  eventually the nqsserver storage will stabilize, but it may take days to do so. vmstat is the tool of choice to observe memory usage.  On AIX vmstat will show  something that may be  startling to some people ... that available free memory ( the 2nd column ) is always  trending toward zero ... no available free memory.  Some customers have concluded that "nearly zero memory free" means it is time to upgrade the server with more real memory.   After the upgrade, the server again shows very little free memory available. Should you be concerned about this?   Many customers are !!  Here is what is happening: - AIX filesystems are built on a paging model.   If you read/write a  filesystem block it is paged into memory ( no read/write system calls ) - This filesystem "page" has its own "backing store" on disk, the original filesystem block.   When the system needs the real memory page holding the file block, there is no need to "page out".    The page can be stolen immediately, because the original is still on disk in the filesystem. - The filesystem  pages tend to collect ... every filesystem block that was ever seen since    system boot is available in memory.  If another application needs the file block, it is retrieved with no physical I/O. What happens if the system does need the memory ... to satisfy a 30MB heap request by nqsserver, for example? - Since the filesystem blocks have their own backing store ( not on a paging device )   the kernel can just steal any filesystem block ... on a least-recently-used basis   to satisfy a new real memory request for "computation pages". No cause for alarm.   vmstat is accurately displaying whether all filesystem blocks have been touched, and now reside in memory.   Back to nqsserver:  when should you be worried about its memory footprint? Answer:  Almost never.   Stop monitoring it ... stop fussing over it ... stop trying to optimize it. This is a production application, and nqsserver uses the memory it requires to accomplish the job, based on demand. C'mon ... never worry?   I'm from New York ... worry is what we do best. Ok, here is the metric you should be watching, using vmstat: - Are you paging ... there are several columns of vmstat outputbash-2.04$ vmstat 3 3 System configuration: lcpu=4 mem=4096MB kthr    memory              page              faults        cpu    ----- ------------ ------------------------ ------------ -----------  r  b    avm   fre  re  pi  po  fr   sr  cy  in   sy  cs us sy id wa  0  0 208492  2600   0   0   0   0    0   0  13   45  73  0  0 99  0  0  0 208492  2600   0   0   0   0    0   0   9   12  77  0  0 99  0  0  0 208492  2600   0   0   0   0    0   0   9   40  86  0  0 99  0 avm is the "available free memory" indicator that trends toward zerore   is "re-page".  The kernel steals a real memory page for one process;  immediately repages back to original processpi  "page in".   A process memory page previously paged out, now paged back in because the process needs itpo "page out" A process memory block was paged out, because it was needed by some other process Light paging activity ( re, pi, po ) is not a concern for worry.   Processes get started, need some memory, go away. Sustained paging activity  is cause for concern.   obiee users are having a terrible day if these counters are always changing. Hang on ... if nqsserver needs that memory and I reduce MAXDATA to keep the process under control, won't the nqsserver process crash when the memory is needed? Yes it will.   It means that nqsserver is configured to require too much memory and there are  lots of options to reduce the real memory requirement.  - number of threads  - size of query cache  - size of sort But I need nqsserver to keep running. Real memory is over-committed.    Many things can cause this:- running all application processes on a single server    ... DB server, web servers, WebLogic/WebSphere, sawserver, nqsserver, etc.   You could move some of those to another host machine and communicate over the network  The need for real memory doesn't go away, it's just distributed to other host machines. - AIX LPAR is configured with too little memory.     The AIX admin needs to provide more real memory to the LPAR running obiee. - More memory to this LPAR affects other partitions. Then it's time to visit your friendly IBM rep and buy more memory.

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  • is it worth defragging an iPod

    - by alimack
    Essentially my 5G iPod was cutting tracks off and generally misbehaving. So I did the following: 1) Use Diskwarrior - heavy directory fragmentation which it fixed; 2) Use iDefrag - some fragmentation but it kept halting as it couldn't move files; 3) Try to write out drive with Disk Utility - got a warning from DU so gave up before I started; 4) Completely restored using iTunes; 5) Reran Diskwarrior - still heavy directory fragmentation; 6) Reran iDefrag, still fragmentation although limited to two bands; The iPod is much quicker to traverse menus and no more track skipping. My question is this - is defragging worth it or does the heat generated by the process kill the drive and make it a self-defeating process. Anyone have any metrics/ figures? Clearly it's a bad idea for solid state drives like the nano & touch.

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  • Android: OutofMemoryError: bitmap size exceeds VM budget with no reason I can see.

    - by Meymann
    Hi. I am having an OutOfMemory exception with a gallery over 600x800 pixels JPEG's. The environment I've been using Gallery with JPG images around 600x800 pixels. Since my content may be a bit more complex than just images, I have set each view to be a RelativeLayout that wraps ImageView with the JPG. In order to "speed up" the user experience I have a simple cache of 4 slots that prefetches (in a looper) about 1 image left and 1 image right to the displayed image and keeps them in a 4 slot HashMap. The platform I am using AVD of 256 RAM and 128 Heap Size, with a 600x800 screen. It also happens on an Entourage Edge target, except that with the device it's harder to debug. The problem I have been getting an exception: OutofMemoryError: bitmap size exceeds VM budget And it happens when fetching the fifth image. I have tried to change the size of my image cache, and it is still the same. The strange thing: There should not be a memory problem In order to make sure the heap limit is very far away from what I need, I have defined a dummy 8MB array in the beginning, and left it unreferenced so it's immediately dispatched. It is a member of the activity thread and is defined as following static { @SuppressWarnings("unused") byte dummy[] = new byte[ 8*1024*1024 ]; } The result is that the heap size is nearly 11MB and it's all free. Note I have added that trick after it began to crash. It makes OutOfMemory less frequent. Now, I am using DDMS. Just before the crash (does not change much after the crash), DDMS shows: ID Heap Size Allocated Free %Used #Objects 1 11.195 MB 2.428 MB 8.767 MB 21.69% 47,156 And in the detail table it shows: Type Count Total Size Smallest Largest Median Average free 1,536 8.739MB 16B 7.750MB 24B 5.825KB The largest block is 7.7MB. And yet the LogCat says: ERROR/dalvikvm-heap(1923): 925200-byte external allocation too large for this process. If you mind the relation of the median and the average, it is plausible to assume that most of the available blocks are very small. However, there is a block large enough for the bitmap, it's 7.7M. How come it is still not enough? Note: I recorded a heap trace. When looking at the amount of data allocated, it does not feel like more than 2M is allocated. It does match the free memory report by DDMS. Could it be that I experience some problem like heap-fragmentation? How do I solve/workaround the problem? Is the heap shared to all threads? Could it be that I interpret the DDMS readout in a wrong way, and there is really no 900K block to allocate? If so, can anybody please tell me where I can see that? Thanks a lot Meymann

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  • Does boost::asio makes excessive small heap allocations or am I wrong?

    - by Poni
    #include <cstdlib> #include <iostream> #include <boost/bind.hpp> #include <boost/asio.hpp> using boost::asio::ip::tcp; class session { public: session(boost::asio::io_service& io_service) : socket_(io_service) { } tcp::socket& socket() { return socket_; } void start() { socket_.async_read_some(boost::asio::buffer(data_, max_length - 1), boost::bind(&session::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } void handle_read(const boost::system::error_code& error, size_t bytes_transferred) { if (!error) { data_[bytes_transferred] = '\0'; if(NULL != strstr(data_, "quit")) { this->socket().shutdown(boost::asio::ip::tcp::socket::shutdown_both); this->socket().close(); // how to make this dispatch "handle_read()" with a "disconnected" flag? } else { boost::asio::async_write(socket_, boost::asio::buffer(data_, bytes_transferred), boost::bind(&session::handle_write, this, boost::asio::placeholders::error)); socket_.async_read_some(boost::asio::buffer(data_, max_length - 1), boost::bind(&session::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } } else { delete this; } } void handle_write(const boost::system::error_code& error) { if (!error) { // } else { delete this; } } private: tcp::socket socket_; enum { max_length = 1024 }; char data_[max_length]; }; class server { public: server(boost::asio::io_service& io_service, short port) : io_service_(io_service), acceptor_(io_service, tcp::endpoint(tcp::v4(), port)) { session* new_session = new session(io_service_); acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session, boost::asio::placeholders::error)); } void handle_accept(session* new_session, const boost::system::error_code& error) { if (!error) { new_session->start(); new_session = new session(io_service_); acceptor_.async_accept(new_session->socket(), boost::bind(&server::handle_accept, this, new_session, boost::asio::placeholders::error)); } else { delete new_session; } } private: boost::asio::io_service& io_service_; tcp::acceptor acceptor_; }; int main(int argc, char* argv[]) { try { if (argc != 2) { std::cerr << "Usage: async_tcp_echo_server <port>\n"; return 1; } boost::asio::io_service io_service; using namespace std; // For atoi. server s(io_service, atoi(argv[1])); io_service.run(); } catch (std::exception& e) { std::cerr << "Exception: " << e.what() << "\n"; } return 0; } While experimenting with boost::asio I've noticed that within the calls to async_write()/async_read_some() there is a usage of the C++ "new" keyword. Also, when stressing this echo server with a client (1 connection) that sends for example 100,000 times some data, the memory usage of this program is getting higher and higher. What's going on? Will it allocate memory for every call? Or am I wrong? Asking because it doesn't seem right that a server app will allocate, anything. Can I handle it, say with a memory pool? Another side-question: See the "this-socket().close();" ? I want it, as the comment right to it says, to dispatch that same function one last time, with a disconnection error. Need that to do some clean-up. How do I do that? Thank you all gurus (:

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  • Best tree/heap data structure for fixed set of nodes with changing values + need top 20 values?

    - by user350139
    I'm writing something like a game in C++ where I have a database table containing the current score for each user. I want to read that table into memory at the start of the game, quickly change each user's score while the game is being played in response to what each user does, and then when the game ends write the current scores back to the database. I also want to be able to find the 20 or so users with the highest scores. No users will be added or deleted during the short period when the game is being played. I haven't tried it yet, but updating the database might take too much time during the period when the game is being played. Fixed set of users (might be 10,000 to 50,000 users) Will map user IDs to their score and other user-specific information. User IDs will be auto_increment values. If the structure has a high memory overhead that's probably not an issue. If the program crashes during gameplay it can just be re-started. Quickly get a user's current score. Quickly add to a user's current score (and return their current score) Quickly get 20 users with highest score. No deletes. No inserts except when the structure is first created, and how long that takes isn't critical. Getting the top 20 users will only happen every five or ten seconds, but getting/adding will happen much more frequently. If not for the last, I could just create a memory block equal to sizeof(user) * max(user id) and put each user at user id * sizeof(user) for fast access. Should I do that plus some other structure for the Top 20 feature, or is there one structure that will handle all of this together?

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  • Check if a pointer points to allocated memory on the heap.

    - by Ugo
    Ok, I know this question seems to have been asked many times on stackoverflow. but please read Well the answer for any address is "No you can't" but the question here is to know if a pointer points to a piece of memory allocated with malloc/new. Actually I think it could be easily implemented overriding malloc/free and keeping track of allocated memory ranges. Do you know a memory management library providing this specific tool ?

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