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  • How to use less memory while running a task in Symfony 1.4?

    - by Guillaume Flandre
    I'm using Symfony 1.4 and Doctrine. So far I had no problem running tasks with Symfony. But now that I have to import a pretty big amount of data and save them in the database, I get the infamous "Fatal Error: Allowed memory size of XXXX bytes exhausted" During this import I'm only creating new objects, setting a few fields and saving them. I'm pretty sure it has something to do with the number of objects I'm creating when saving data. Unsetting those objects doesn't do anything though. Are there any best practices to limit memory usage in Symfony?

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  • How does memory management in Java and C# differ?

    - by David Johnstone
    I was reading through 2010 CWE/SANS Top 25 Most Dangerous Programming Errors and one of the entries is for Buffer Copy without Checking Size of Input. It suggests using a language with features to prevent or mitigate this problem, and says: For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. I was not aware that Java and C# differed in any meaningful way with regard to memory management. How is it that Java is not subject to buffer overflows, while C# only protects against overflows? And how is it possible to disable this protection in C#?

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  • Practical rules for premature optimization

    - by DougW
    It seems that the phrase "Premature Optimization" is the buzz-word of the day. For some reason, iphone programmers in particular seem to think of avoiding premature optimization as a pro-active goal, rather than the natural result of simply avoiding distraction. The problem is, the term is beginning to be applied more and more to cases that are completely inappropriate. For example, I've seen a growing number of people say not to worry about the complexity of an algorithm, because that's premature optimization (eg http://stackoverflow.com/questions/2190275/help-sorting-an-nsarray-across-two-properties-with-nssortdescriptor/2191720#2191720). Frankly, I think this is just laziness, and appalling to disciplined computer science. But it has occurred to me that maybe considering the complexity and performance of algorithms is going the way of assembly loop unrolling, and other optimization techniques that are now considered unnecessary. What do you think? Are we at the point now where deciding between an O(n^n) and O(n!) complexity algorithm is irrelevant? What about O(n) vs O(n*n)? What do you consider "premature optimization"? What practical rules do you use to consciously or unconsciously avoid it? This is a bit vague, but I'm curious to hear other peoples' opinions on the topic.

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  • "Thread-Safe Calls" with "Invoke" method to Winform control leads very heavy memory leak!!

    - by konnychen
    In the following link: "Make Thread-Safe Calls to Windows Forms Controls http://msdn.microsoft.com/en-us/library/ms171728.aspx" We can see an example which provide cross tread access to a winform control. But if the thread is in a while loop, it will cause the heavy memory leak. As I use taskmanage I can see the memory is increasing. Can anyone help me to solve the problem? oThread2 = new Thread(new ThreadStart(Cyclic_Call)); oThread2.Start(); delegate void SetText_lab_Statubar(string text); private void m_SetText_lab_Statubar(string text) { if (this.lab_Statubar.InvokeRequired) { SetText_lab_Statubar d = new SetText_lab_Statubar(m_SetText_lab_Statubar); this.Invoke(d, new object[] { text }); } else { this.lab_Statubar.Text = text; } } private void Cyclic_Call() { do { this.m_SetText_lab_Statubar("This string is set from thread"); Thread.Sleep(100); } while (!b_AbortThraed); }

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  • how can c# help in drawing using memory layers concept?

    - by moon
    hello all i am facing problem in drawing dynamically in a picture box. i works very good when the drawing objects are few but as the drawing objects increases the response time of my GUI is getting worse and worse, my GUI works very well up to 90 drawing objects but i have to support more than 1000 so this technique didn't work for me. know i have decided to adopt layers mechanism, i mean i will draw different layers of drawing in memory and then XOR them to load the final image to my display. the question is "i Can play directly with memory do draw layers using C# (Examples needed?)" other ideas are also appreciated, (Drawing objects means the shapes line,circles etc. that i have to draw on my GUI) thanx in advance

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  • Are memory barriers necessary for atomic reference counting shared immutable data?

    - by Dietrich Epp
    I have some immutable data structures that I would like to manage using reference counts, sharing them across threads on an SMP system. Here's what the release code looks like: void avocado_release(struct avocado *p) { if (atomic_dec(p->refcount) == 0) { free(p->pit); free(p->juicy_innards); free(p); } } Does atomic_dec need a memory barrier in it? If so, what kind of memory barrier? Additional notes: The application must run on PowerPC and x86, so any processor-specific information is welcomed. I already know about the GCC atomic builtins. As for immutability, the refcount is the only field that changes over the duration of the object.

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  • Will it use more and more memory if I keep drawing on the UIView?

    - by Tattat
    This is my drawRect: CGContextRef context = UIGraphicsGetCurrentContext(); CGContextSetLineWidth(context, 2.0); CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor); CGContextMoveToPoint(context, x1, y1); CGContextAddLineToPoint(context, x2, y2); CGContextStrokePath(context); If I run this code thousand times or more. My UIView will have many lines on that. Will it use more memory than only just one line on it? Er... ...I mean, will the program remember the line I draw or after it draw the lines, it won't have any information in the memory. thz .

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  • How can I avoid "Your system is running low on virtual memory" pop-up?

    - by Xavier Nodet
    Our application sometimes uses a lot of memory, and this is expected. But when we test it under high load on Windows XP, we usually get the very annoying "Your system is running low on virtual memory" popup, and this prevents our automated, unattended, tests to run through... Is it possible to prevent this popup to appear, and just have the allocation fail? The app will handle it gracefully, and tests will go on... We are using Windows XP, but if a solution only exists on later versions, I'd be happy to know anyway.

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  • ASP.NET web services leak memory when (de)serializing disposable objects?

    - by Serilla
    In the following two cases, if Customer is disposable (implementing IDisposable), I believe it will not be disposed by ASP.NET, potentially being the cause of a memory leak: [WebMethod] public Customer FetchCustomer(int id) { return new Customer(id); } [WebMethod] public void SaveCustomer(Customer value) { // save it } This flaw applies to any IDisposable object. So returning a DataSet from a ASP.NET web service, for example, will also result in a memory leak - the DataSet will not be disposed. In my case, Customer opened a database connection which was cleaned up in Dispose - except Dispose was never called resulting in loads of unclosed database connections. I realise there a whole bunch of bad practices being followed here (its only an example anyway), but the point is that ASP.NET - the (de)serializer - is responsible for disposing these objects, so why doesn't it? This is an issue I was aware of for a while, but never got to the bottom of. I'm hoping somebody can confirm what I have found, and perhaps explain if there is a way of dealing with it.

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  • Need to allocate memory before a Delphi string copy?

    - by Duncan
    Do I need to allocate memory when performing a Delphi string copy? I've a function which posts a Windows message to another form in my application. It looks something like this: // Note: PThreadMessage = ^TThreadMessage; TThreadMessage = String; function PostMyMessage( aStr : string ); var gMsgPtr : PThreadMessage; gStrLen : Integer; begin New(gMsgPtr); gStrLen := StrLen(PWideChar(aMsg)); gMsgPtr^ := Copy(aMsg, 0, gStrLen); PostMessage(ParentHandle, WM_LOGFILE, aLevel, Integer(gMsgPtr)); // Prevent Delphi from freeing this memory before consumed. LParam(gMsgPtr) := 0; end;

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  • What is the best solution to replace a new memory allocator in an existing code?

    - by O. Askari
    During the last few days I've gained some information about memory allocators other than the standard malloc(). There are some implementations that seem to be much better than malloc() for applications with many threads. For example it seems that tcmalloc and ptmalloc have better performance. I have a C++ application that uses both malloc and new operators in many places. I thought replacing them with something like ptmalloc may improve its performance. But I wonder how does the new operator act when used in C++ application that runs on Linux? Does it use the standard behavior of malloc or something else? What is the best way to replace the new memory allocator with the old one in the code? Is there any way to override the behavior or new and malloc or do I need to replace all the calls to them one by one?

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  • Does remove a DOM object (in Javascript) will cause Memory leak if it has event attached?

    - by seatoskyhk
    So, if in the javascript, I create a DOM object in the HTML page, and attach event listener to the DOM object, upon I remove the the DOM from HTML page, does the event listener still exist and causing memory leak? function myTest() { var obj = document.createElement('div'); obj.addEventListener('click', function() {alert('whatever'); }); var body = document.getElementById('body'); // assume there is a <div id='body'></div> already body.appendChild(obj); } // then after some user actions. I call this: function emptyPage() { var body = document.getElementById('body'); body.innerHTML = ''; //empty it. } So, the DOM object, <div> inside body is gone. But what about the eventlistener? I'm just afraid that it will cause memory leak.

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  • SQL SERVER – Video – Beginning Performance Tuning with SQL Server Execution Plan

    - by pinaldave
    Traveling can be most interesting or most exhausting experience. However, traveling is always the most enlightening experience one can have. While going to long journey one has to prepare a lot of things. Pack necessary travel gears, clothes and medicines. However, the most essential part of travel is the journey to the destination. There are many variations one prefer but the ultimate goal is to have a delightful experience during the journey. Here is the video available which explains how to begin with SQL Server Execution plans. Performance Tuning is a Journey Performance tuning is just like a long journey. The goal of performance tuning is efficient and least resources consuming query execution with accurate results. Just as maps are the most essential aspect of performance tuning the same way, execution plans are essentially maps for SQL Server to reach to the resultset. The goal of the execution plan is to find the most efficient path which translates the least usage of the resources (CPU, memory, IO etc). Execution Plans are like Maps When online maps were invented (e.g. Bing, Google, Mapquests etc) initially it was not possible to customize them. They were given a single route to reach to the destination. As time evolved now it is possible to give various hints to the maps, for example ‘via public transport’, ‘walking’, ‘fastest route’, ‘shortest route’, ‘avoid highway’. There are places where we manually drag the route and make it appropriate to our needs. The same situation is with SQL Server Execution Plans, if we want to tune the queries, we need to understand the execution plans and execution plans internals. We need to understand the smallest details which relate to execution plan when we our destination is optimal queries. Understanding Execution Plans The biggest challenge with maps are figuring out the optimal path. The same way the  most common challenge with execution plans is where to start from and which precise route to take. Here is a quick list of the frequently asked questions related to execution plans: Should I read the execution plans from bottoms up or top down? Is execution plans are left to right or right to left? What is the relational between actual execution plan and estimated execution plan? When I mouse over operator I see CPU and IO but not memory, why? Sometime I ran the query multiple times and I get different execution plan, why? How to cache the query execution plan and data? I created an optimal index but the query is not using it. What should I change – query, index or provide hints? What are the tools available which helps quickly to debug performance problems? Etc… Honestly the list is quite a big and humanly impossible to write everything in the words. SQL Server Performance:  Introduction to Query Tuning My friend Vinod Kumar and I have created for the same a video learning course for beginning performance tuning. We have covered plethora of the subject in the course. Here is the quick list of the same: Execution Plan Basics Essential Indexing Techniques Query Design for Performance Performance Tuning Tools Tips and Tricks Checklist: Performance Tuning We believe we have covered a lot in this four hour course and we encourage you to go over the video course if you are interested in Beginning SQL Server Performance Tuning and Query Tuning. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology, Video Tagged: Execution Plan

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  • SQL SERVER – Generate Report for Index Physical Statistics – SSMS

    - by pinaldave
    Few days ago, I wrote about SQL SERVER – Out of the Box – Activity and Performance Reports from SSSMS (Link). A user asked me a question regarding if we can use similar reports to get the detail about Indexes. Yes, it is possible to do the same. There are similar type of reports are available at Database level, just like those available at the Server Instance level. You can right click on Database name and click Reports. Under Standard Reports, you will find following reports. Disk Usage Disk Usage by Top Tables Disk Usage by Table Disk Usage by Partition Backup and Restore Events All Transactions All Blocking Transactions Top Transactions by Age Top Transactions by Blocked Transactions Count Top Transactions by Locks Count Resource Locking Statistics by Objects Object Execute Statistics Database Consistency history Index Usage Statistics Index Physical Statistics Schema Change history User Statistics Select the Reports with name Index Physical Statistics. Once click, a report containing all the index names along with other information related to index will be visible, e.g. Index Type and number of partitions. One column that caught my interest was Operation Recommended. In some place, it suggested that index needs to be rebuilt. It is also possible to click and expand the column of partitions and see additional details about index as well. DBA and Developers who just want to have idea about how your index is and its physical statistics can use this tool. Click to Enlarge Note: Please note that I will rebuild my indexes just because this report is recommending it. There are many other parameters you need to consider before rebuilding indexes. However, this tool gives you the accurate stats of your index and it can be right away exported to Excel or PDF writing by clicking on the report. Reference : Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Index, SQL Optimization, SQL Performance, SQL Query, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, SQL Utility, T SQL, Technology

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  • SQL SERVER – Subquery or Join – Various Options – SQL Server Engine knows the Best

    - by pinaldave
    This is followup post of my earlier article SQL SERVER – Convert IN to EXISTS – Performance Talk, after reading all the comments I have received I felt that I could write more on the same subject to clear few things out. First let us run following four queries, all of them are giving exactly same resultset. USE AdventureWorks GO -- use of = SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID = ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA WHERE EA.EmployeeID = E.EmployeeID) GO -- use of in SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID IN ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA WHERE EA.EmployeeID = E.EmployeeID) GO -- use of exists SELECT * FROM HumanResources.Employee E WHERE EXISTS ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA WHERE EA.EmployeeID = E.EmployeeID) GO -- Use of Join SELECT * FROM HumanResources.Employee E INNER JOIN HumanResources.EmployeeAddress EA ON E.EmployeeID = EA.EmployeeID GO Let us compare the execution plan of the queries listed above. Click on image to see larger image. It is quite clear from the execution plan that in case of IN, EXISTS and JOIN SQL Server Engines is smart enough to figure out what is the best optimal plan of Merge Join for the same query and execute the same. However, in the case of use of Equal (=) Operator, SQL Server is forced to use Nested Loop and test each result of the inner query and compare to outer query, leading to cut the performance. Please note that here I no mean suggesting that Nested Loop is bad or Merge Join is better. This can very well vary on your machine and amount of resources available on your computer. When I see Equal (=) operator used in query like above, I usually recommend to see if user can use IN or EXISTS or JOIN. As I said, this can very much vary on different system. What is your take in above query? I believe SQL Server Engines is usually pretty smart to figure out what is ideal execution plan and use it. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Joins, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Subquery or Join – Various Options – SQL Server Engine Knows the Best – Part 2

    - by pinaldave
    This blog post is part 2 of the earlier written article SQL SERVER – Subquery or Join – Various Options – SQL Server Engine knows the Best by Paulo R. Pereira. Paulo has left excellent comment to earlier article once again proving the point that SQL Server Engine is smart enough to figure out the best plan itself and uses the same for the query. Let us go over his comment as he has posted. “I think IN or EXISTS is the best choice, because there is a little difference between ‘Merge Join’ of query with JOIN (Inner Join) and the others options (Left Semi Join), and JOIN can give more results than IN or EXISTS if the relationship is 1:0..N and not 1:0..1. And if I try use NOT IN and NOT EXISTS the query plan is different from LEFT JOIN too (Left Anti Semi Join vs. Left Outer Join + Filter). So, I found a case where EXISTS has a different query plan than IN or ANY/SOME:” USE AdventureWorks GO -- use of SOME SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID = SOME ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA UNION ALL SELECT EA.EmployeeID FROM HumanResources.EmployeeDepartmentHistory EA ) -- use of IN SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID IN ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA UNION ALL SELECT EA.EmployeeID FROM HumanResources.EmployeeDepartmentHistory EA ) -- use of EXISTS SELECT * FROM HumanResources.Employee E WHERE EXISTS ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA UNION ALL SELECT EA.EmployeeID FROM HumanResources.EmployeeDepartmentHistory EA ) When looked into execution plan of the queries listed above indeed we do get different plans for queries and SQL Server Engines creates the best (least cost) plan for each query. Click on image to see larger images. Thanks Paulo for your wonderful contribution. Reference : Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, Readers Contribution, SQL, SQL Authority, SQL Joins, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Activity Monitor and Performance Issue

    - by pinaldave
    We had wonderful SQLAuthority News – Community Tech Days – December 11, 2010 event yesterday. After the event, we had meeting among Jacob Sebastian, Vinod Kumar, Rushabh Mehta and myself. We all were sharing our experience about performance tuning consultations. During the conversation, Jacob has shared wonderful story of his recent observation. The story is very small but the moral of the story is very important. The story is about a client, who had continuously performance issues. Client used Activity Monitor (Read More: SQL SERVER – 2008 – Location of Activity Monitor – Where is SQL Serve Activity Monitor Located) to check the performance issues. The pattern of the performance issues was very much common all the time. Every time, after a while the computer stopped responding. After doing in-depth performance analysis, Jacob realized that client once opened activity monitor never closed it. The same activity monitor itself is very expensive process. The tool, which helped to debug the performance issues, also helped (negatively) to bring down the server. After closing the activity monitor which was open for long time, the server did not have performance issues. Moral of the story: Activity Monitor is great tool but use it with care and close it when not needed. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Best Practices, Pinal Dave, SQL, SQL Authority, SQL Optimization, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQLAuthority News – Statistics and Best Practices – Virtual Tech Days – Nov 22, 2010

    - by pinaldave
    I am honored that I have been invited to speak at Virtual TechDays on Nov 22, 2010 by Microsoft. I will be speaking on my favorite subject of Statistics and Best Practices. This exclusive online event will have 80 deep technical sessions across 3 days – and, attendance is completely FREE. There are dedicated tracks for Architects, Software Developers/Project Managers, Infrastructure Managers/Professionals and Enterprise Developers. So, REGISTER for this exclusive online event TODAY. Statistics and Best Practices Timing: 11:45am-12:45pm Statistics are a key part of getting solid performance. In this session we will go over the basics of the statistics and various best practices related to Statistics. We will go over various frequently asked questions like a) when to update statistics, b) different between sync and async update of statistics c) best method to update statistics d) optimal interval of updating statistics. We will also discuss the pros and cons of the statistics update. This session is for all of you – whether you’re a DBA or developer! You can register for this event over here. If you have never attended my session on this subject I strongly suggest that you attend the event as this is going to be very interesting conversation between us. If you have attended this session earlier, this will contain few new information which will for sure interesting to share with all. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: MVP, Pinal Dave, SQL, SQL Authority, SQL Joins, SQL Optimization, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority News, T SQL, Technology Tagged: SQL Statistics, Statistics

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