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• Improving I/O performance in C++ programs[external merge sort]

  - by Ajay

  I am currently working on a project involving external merge-sort using replacement-selection and k-way merge. I have implemented the project in C++[runs on linux]. Its very simple and right now deals with only fixed sized records. For reading & writing I use (i/o)fstream classes. After executing the program for few iterations, I noticed that I/O read blocks for requests of size more than 4K(typical block size). Infact giving buffer sizes greater than 4K causes performance to decrease. The output operations does not seem to need buffering, linux seemed to take care of buffering output. So I issue a write(record) instead of maintaining special buffer of writes and then flushing them out at once using write(records[]). But the performance of the application does not seem to be great. How could I improve the performance? Should I maintain special I/O threads to take care of reading blocks or are there existing C++ classes providing this abstraction already?(Something like BufferedInputStream in java)

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• JDBC programms running long time performance issue

  - by phyerbarte

  My program has an issue with Oracle query performance, I believe the SQL have good performance, because it returns quickly in SQLPlus. But when my program has been running for a long time, like 1 week, the SQL query (using JDBC) becomes slower (In my logs, the query time is much longer than when I originally started the program). When I restart my program, the query performance comes back to normal. I think it is could be something wrong with the way I use the preparedStatement, because the SQL I'm using does not use placeholders "?" at all. Just a complex select query. The query process is done by a util class. Here is the pertinent code building the query: public List<String[]> query(String sql, String[] args) { Connection conn = null; conn = openConnection(); conn.setAutocommit(true); .... PreparedStatement preStatm = null; ResultSet rs = null; ....//set preparedstatment arg code rs = preStatm.executeQuery(); .... finally{ //close rs //close prestatm //close connection } } In my case, the args is always null, so it just passes a query sql to this query method. Is that possible this way could slow down the DB query after program long time running? Or I should use statement instead, or just pass args with "?" in the SQL? How can I find out the root cause for my issue? Thanks.

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• Essbase Analytics Link (EAL) - Performance of some operation of EAL could be improved by tuning of EAL Data Synchronization Server (DSS) parameters

  - by Ahmed Awan

  Generally, performance of some operation of EAL (Essbase Analytics Link) could be improved by tuning of EAL Data Synchronization Server (DSS) parameters. a. Expected that DSS machine will be 64-bit machine with 4-8 cores and 5-8 GB of RAM dedicated to DSS. b. To change DSS configuration - open EAL Configuration Tool on DSS machine.     ->Next:     and define: "Job Units" as <Number of Cores dedicated to DSS> * 1.5 "Max Memory Size" (if this is 64-bit machine) - ~1G for each Job Unit. If DSS machine is 32-bit - max memory size is 2600 MB. "Data Store Size" - depends on number of bridges and volume of HFM applications, but in most cases 50000 MB is enough. This volume should be available in defined "Data Store Dir" driver.   Continue with configuration and finish it. After that, DSS should be restarted to take new definitions.  

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• Why is Python used for high-performance/scientific computing (but Ruby isn't)?

  - by Cyclops

  There's a quote from a PyCon 2011 talk that goes: At least in our shop (Argonne National Laboratory) we have three accepted languages for scientific computing. In this order they are C/C++, Fortran in all its dialects, and Python. You’ll notice the absolute and total lack of Ruby, Perl, Java. It was in the more general context of high-performance computing. Granted the quote is only from one shop, but another question about languages for HPC, also lists Python as one to learn (and not Ruby). Now, I can understand C/C++ and Fortran being used in that problem-space (and Perl/Java not being used). But I'm surprised that there would be a major difference in Python and Ruby use for HPC, given that they are fairly similar. (Note - I'm a fan of Python, but have nothing against Ruby). Is there some specific reason why the one language took off? Is it about the libraries available? Some specific language features? The community? Or maybe just historical contigency, and it could have gone the other way?

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• Information about rendering, batches, the graphical card, performance etc. + XNA?

  - by Aidiakapi

  I know the title is a bit vague but it's hard to describe what I'm really looking for, but here goes. When it comes to CPU rendering, performance is mostly easy to estimate and straightforward, but when it comes to the GPU due to my lack of technical background information, I'm clueless. I'm using XNA so it'd be nice if theory could be related to that. So what I actually wanna know is, what happens when and where (CPU/GPU) when you do specific draw actions? What is a batch? What influence do effects, projections etc have? Is data persisted on the graphics card or is it transferred over every step? When there's talk about bandwidth, are you talking about a graphics card internal bandwidth, or the pipeline from CPU to GPU? Note: I'm not actually looking for information on how the drawing process happens, that's the GPU's business, I'm interested on all the overhead that precedes that. I'd like to understand what's going on when I do action X, to adapt my architectures and practices to that. Any articles (possibly with code examples), information, links, tutorials that give more insight in how to write better games are very much appreciated. Thanks :)

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• Higher Performance With Spritesheets Than With Rotating Using C# and XNA 4.0?

  - by Manuel Maier

  I would like to know what the performance difference is between using multiple sprites in one file (sprite sheets) to draw a game-character being able to face in 4 directions and using one sprite per file but rotating that character to my needs. I am aware that the sprite sheet method restricts the character to only be able to look into predefined directions, whereas the rotation method would give the character the freedom of "looking everywhere". Here's an example of what I am doing: Single Sprite Method Assuming I have a 64x64 texture that points north. So I do the following if I wanted it to point east: spriteBatch.Draw( _sampleTexture, new Rectangle(200, 100, 64, 64), null, Color.White, (float)(Math.PI / 2), Vector2.Zero, SpriteEffects.None, 0); Multiple Sprite Method Now I got a sprite sheet (128x128) where the top-left 64x64 section contains a sprite pointing north, top-right 64x64 section points east, and so forth. And to make it point east, i do the following: spriteBatch.Draw( _sampleSpritesheet, new Rectangle(400, 100, 64, 64), new Rectangle(64, 0, 64, 64), Color.White); So which of these methods is using less CPU-time and what are the pro's and con's? Is .NET/XNA optimizing this in any way (e.g. it notices that the same call was done last frame and then just uses an already rendered/rotated image thats still in memory)?

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• Best XPath tools

  - by Sayed Ibrahim Hashimi

  What tools are you guys using for XPath and why? Right now I'm using SketchPath because its totally awesome, but its a windows app that needs to be installed WhiteBeam online XPath test bedbecause you can test expressions from the website SketchPath seems to stand out the most to me because it actually helps you create the xpath and it is very advanced. If you haven't tried it you should. Cons to SketchPath: you have to install it on the machine, otherwise it is fantastic. Cons to WhiteBeam: you have to upload your file which I don't always want to do for security reasons and the file size you can upload has some limit on it, and uploading a file is annoying anyways. Also I think there might be some subtle differences between the xpath used for that tool and when running a .NET app. But don't remember any right now. Just keep it in mind.

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• Getting ID of an instance newly launched with ec2-api-tools

  - by Jonik

  I'm launching an EC2 instance, by invoking ec2-run-instances from simple a bash script, and want to perform further operations on that instance (e.g. associate elastic IP), for which I need the instance id. The command is something like ec2-run-instances ami-dd8ea5a9 -K pk.pem -C cert.pem --region eu-west-1 -t c1.medium -n 1, and its output: RESERVATION r-b6ea58c1 696664755663 default INSTANCE i-945af9e3 ami-dd8ea5b9 pending 0 c1.medium 2010-04-15T10:47:56+0000 eu-west-1a aki-b02a01c4 ari-39c2e94d In this example, i-945af9e3 is the id I'm after. So, I'd need a simple way to parse the id from what the command returns - how would you go about doing it? My AWK is a little rusty... Feel free to use any tool available on a typical Linux box. (If there's a way to get it directly using EC2-API-tools, all the better. But afaik there's no EC2 command to e.g. return the id of the most recently launched instance.)

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• Tools for website development

  - by sharkin

  Hi! I can't find any other post which addresses this topic on a purely general level. I'm very unexperienced in developing full scale websites. I get around using HTML and PHP for simple tasks. Now I'm looking at developing a more elaborate site and want to get hold of a good tool which doesn't eat my wallet to the bones. I guess I should add more intelligent text here about what I expect it to be capable of, but I really don't know so much. I guess the code/design/preview style in dreamweaver appealed to me, and I'm definetely going to use scripting like PHP or ASP.NET, some database work etc. I guess pretty much the standard (?) website development tasks. So, are there good tools out there I should be looking at?

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• Free Online tools for testing mysql queries - having features like PhPMyAdmin

  - by Sandeepan Nath

  Can anybody tell me any "free online hosted database servers" (don't know if that is the correct term) where we can do query testing and all those things that we can do on tools like PhpMyAdmin? does something like that exist? Like we have http://jsfiddle.net/ for testing js codes. I checked http://sqlzoo.net/ but this is very much limited and there are some predefined tables in some given examples on which we can alter things. That's all. It does not allow me to do a lots of other things like creating tables etc. A nice resource - PhpMyAdmin's demo site . Use the latest stable version here. You have full control over the MySQL server, however you should not change root, debian-sys-maint or pma user password or limit their permissions. If you do so, demo can not be accessed until privileges are restored, so you just break things for you and other users.

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• Searching for known Team Development helper tools

  - by John

  Hello, My team is small, only two programmers.We both share one source ,but we live in different places.The problem is that Meanwhile I make changes on our project,the other team worker makes changes as well.It's very hard to write down every change,at least for us. When we decide we've made an important change,we contact each other sending the whole project's source. This is not good,because: The files sent from one do not contain the changes that the other worker has been working on meanwhile. We host the source on free servers,thus makes it possible for other to see the files.It will be VERY much better if only few(those that are changed) files are being uploaded rather than the whole project. My question: Are there any tools that could make our lives easier? Thanks in advance! EDIT: We use Delphi 2009.

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• @SequenceGenerator - allocationSize, reverse engineering with Eclipse Hibernate Tools

  - by Spooky

  I use the Eclipse Hibernate Tools to create domain classes with JPA annotations from my Oracle database. To control sequence generation I have added the following entry to the hibernate.reveng.xml: ... <primary-key> <generator class="sequence"> <param name="sequence">SEQ_FOO_ID</param> </generator> </primary-key> ... This results in the following annotation: @SequenceGenerator(name = "generator", sequenceName = "SEQ_FOO_ID") However I need to set the "allocationSize" like this: @SequenceGenerator(name = "generator", sequenceName = "SEQ_FOO_ID", allocationSize = 1) Is it possible to set this somehow in the hibernate.reveng.xml?

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• Best Tools for Software Maintenance Engineering

  - by Pev

  Yes, the dreaded 'M' word. You've got a workstation, source control and half a million lines of source code that you didn't write. The documentation was out of date the moment that it was approved and published. The original developers are LTAO, at the next project/startup/loony bin and not answering email. What are you going to do? {favourite editor} and Grep will get you started on your spelunking through the gnarling guts of the code base but what other tools should be in the maintenance engineers toolbox? To start the ball-rolling; I don't think I could live without source-insight for C/C++ spelunking. (DISCLAIMER: I don't work for 'em).

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• Best data recovery tools?

  - by Nonick

  So due to a recent act of stupidity and bravado, I uttered the words "backups! who needs backups?!" and what followed was the tragic loss of 260gb of data. This scenario in particular is requiring me to recover a repartitioned hard disk, but I was wondering what tools people here use in general to recover lost data. I'm sure everyone has been there, either accidentally rewriting files, resaving an old version, computer crash, hard disk death, user deletes an important document etc. So was thinking it might be an interesting point of discussion as to what you guys use to recover lost data. I appologise if this is considered irrelevant, but considering there has been a few recovery questions, I think this might be interesting.

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• Very large database, very small portion most being retrieved in real time

  - by mingyeow

  Hi folks, I have an interesting database problem. I have a DB that is 150GB in size. My memory buffer is 8GB. Most of my data is rarely being retrieved, or mainly being retrieved by backend processes. I would very much prefer to keep them around because some features require them. Some of it (namely some tables, and some identifiable parts of certain tables) are used very often in a user facing manner How can I make sure that the latter is always being kept in memory? (there is more than enough space for these) More info: We are on Ruby on rails. The database is MYSQL, our tables are stored using INNODB. We are sharding the data across 2 partitions. Because we are sharding it, we store most of our data using JSON blobs, while indexing only the primary keys

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• c++ ide & tools with clang integration

  - by lurscher

  recently i read this blog about google integrating clang parser into their code analysis tools This is something in which c++ is at least a decade behind other languages like java, but now that llvm-clang is almost c++ iso-ready, i think its possible for c++ code analysis tools to begin using the c++ parser effectively, since it has been designed from the ground up precisely for this so i'm wondering if there are existing open source or known commercial projects taking this path, integrating with clang to provide higher-level analysis tools?

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• Edinburgh this Thurs (25th) - Rob Carrol talks about how to build a high performance, scalable repor

  - by tonyrogerson

  Scottish Area SQL Server User Group Meeting, Edinburgh - Thursday 25th March An evening of SQL Server 2008 Reporting Services Scalability and Performance with Rob Carrol, see how to build a high performance, scalable reporting platform and the tuning techniques required to ensure that report performance remains optimal as your platform grows. Pizza and drinks will be provided! Register at http://www.sqlserverfaq.com/events/221/SQL-Server-2008-Reporting-Services-Scalability-and-Performance.aspx...(read more)

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• SQL SERVER – Maximize Database Performance with DB Optimizer – SQL in Sixty Seconds #054

  - by Pinal Dave

  Performance tuning is an interesting concept and everybody evaluates it differently. Every developer and DBA have different opinion about how one can do performance tuning. I personally believe performance tuning is a three step process Understanding the Query Identifying the Bottleneck Implementing the Fix While, we are working with large database application and it suddenly starts to slow down. We are all under stress about how we can get back the database back to normal speed. Most of the time we do not have enough time to do deep analysis of what is going wrong as well what will fix the problem. Our primary goal at that time is to just fix the database problem as fast as we can. However, here is one very important thing which we need to keep in our mind is that when we do quick fix, it should not create any further issue with other parts of the system. When time is essence and we want to do deep analysis of our system to give us the best solution we often tend to make mistakes. Sometimes we make mistakes as we do not have proper time to analysis the entire system. Here is what I do when I face such a situation – I take the help of DB Optimizer. It is a fantastic tool and does superlative performance tuning of the system. Everytime when I talk about performance tuning tool, the initial reaction of the people is that they do not want to try this as they believe it requires lots of the learning of the tool before they use it. It is absolutely not true with the case of the DB optimizer. It is a very easy to use and self intuitive tool. Once can get going with the product, in no time. Here is a quick video I have build where I demonstrate how we can identify what index is missing for query and how we can quickly create the index. Entire three steps of the query tuning are completed in less than 60 seconds. If you are into performance tuning and query optimization you should download DB Optimizer and give it a go. Let us see the same concept in following SQL in Sixty Seconds Video: You can Download DB Optimizer and reproduce the same Sixty Seconds experience. Related Tips in SQL in Sixty Seconds: Performance Tuning – Part 1 of 2 – Getting Started and Configuration Performance Tuning – Part 2 of 2 – Analysis, Detection, Tuning and Optimizing What would you like to see in the next SQL in Sixty Seconds video? Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Database, Pinal Dave, PostADay, SQL, SQL Authority, SQL in Sixty Seconds, SQL Interview Questions and Answers, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology, Video Tagged: Identity

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• Exchange 2010 - resolving Calendar Attendant\Requests Failed

  - by marcwenger

  On my mailbox server, I am receiving the alert: MSExchange Calendar Attendant\Requests Failed Or in Solarwinds Requests Failed (Calendar Attendant) for Exchange 2010 Mailbox Role Counters (Advanced) on *servername* All I know is this figure should be 0 at all times. Currently I am at 2 and this is the only alert on the Exchange servers. No where I can find how to resolve this. How can I fix this? thank you

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• Need help tuning Mysql and linux server

  - by Newtonx

  We have multi-user application (like MailChimp,Constant Contact) . Each of our customers has it's own contact's list (from 5 to 100.000 contacts). Everything is stored in one BIG database (currently 25G). Since we released our product we have the following data history. 5 years of data history : - users/customers (200+) - contacts (40 million records) - campaigns - campaign_deliveries (73.843.764 records) - campaign_queue ( 8 millions currently ) As we get more users and table records increase our system/web app is getting slower and slower . Some queries takes too long to execute . SCHEMA Table contacts --------------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +---------------------+------------------+------+-----+---------+----------------+ | contact_id | int(10) unsigned | NO | PRI | NULL | auto_increment | | client_id | int(10) unsigned | YES | | NULL | | | name | varchar(60) | YES | | NULL | | | mail | varchar(60) | YES | MUL | NULL | | | verified | int(1) | YES | | 0 | | | owner | int(10) unsigned | NO | MUL | 0 | | | date_created | date | YES | MUL | NULL | | | geolocation | varchar(100) | YES | | NULL | | | ip | varchar(20) | YES | MUL | NULL | | +---------------------+------------------+------+-----+---------+----------------+ Table campaign_deliveries +---------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +---------------+------------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | newsletter_id | int(10) unsigned | NO | MUL | 0 | | | contact_id | int(10) unsigned | NO | MUL | 0 | | | sent_date | date | YES | MUL | NULL | | | sent_time | time | YES | MUL | NULL | | | smtp_server | varchar(20) | YES | | NULL | | | owner | int(5) | YES | MUL | NULL | | | ip | varchar(20) | YES | MUL | NULL | | +---------------+------------------+------+-----+---------+----------------+ Table campaign_queue +---------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +---------------+------------------+------+-----+---------+----------------+ | queue_id | int(10) unsigned | NO | PRI | NULL | auto_increment | | newsletter_id | int(10) unsigned | NO | MUL | 0 | | | owner | int(10) unsigned | NO | MUL | 0 | | | date_to_send | date | YES | | NULL | | | contact_id | int(11) | NO | MUL | NULL | | | date_created | date | YES | | NULL | | +---------------+------------------+------+-----+---------+----------------+ Slow queries LOG -------------------------------------------- Query_time: 350 Lock_time: 1 Rows_sent: 1 Rows_examined: 971004 SELECT COUNT(*) as total FROM contacts WHERE (contacts.owner = 70 AND contacts.verified = 1); Query_time: 235 Lock_time: 1 Rows_sent: 1 Rows_examined: 4455209 SELECT COUNT(*) as total FROM contacts WHERE (contacts.owner = 2); How can we optimize it ? Queries should take no more than 30 secs to execute? Can we optimize it and keep all data in one BIG database or should we change app's structure and set one single database to each user ? Thanks

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• On Windows it's possible to monitor the hard faults for each process?

  - by Renan Vinícius Mozone

  I'm tuning a production server that runs Windows Server 2003 SP2. I want to monitor the hard faults (read an write separately) for each process. Is it possible?

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• Server configurations for hosting MySQL database

  - by shyam

  I have a web application which uses a MySQL database hosted on a virtual server. I've been using this server when I started the application and when the database was really small. Now it has grown and the server is not able to handle the db, causing frequent db errors. I'm planning to get a server and I need suggestions for that. Like I said, the db is now 9 GB, and is growing considerably fast. There are a number of tables with millions of rows, which are frequently updated and queried. The most frequent error the db shows is Lock wait timeout exceeded. Previously there used to be "The total number of locks exceeds the lock table size" errors too, but I could avoid it by increasing Innodb buffer pool size. Please suggest what configurations should I look for in the server I should buy. I read somewhere that the db should ideally have a buffer pool size greater than the size of its data, so in my case I guess I'd need memory gt 9 GB. What other things should I look for in the server? Just tell me if I should give you more info about the

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• Do you own your tools?

  - by Mike Brown

  A colleague of mine wrote a post a while ago asking Do you own your tools. It raises an important question. Do you? I answered way down in the comments. As an independent, I do own my tools. Even when I wasn't independent, I had my own (fully licensed) tools that I used for personal development. I don't think buying your own tools are something to puff your chest up about (just because you can buy a $100 pair of basketball sneakers they won't make you as good as Michael Jordan), but it IS an investment in yourself that shouldn't be taken lightly. What do you think good people?

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• Find out which task is generating a lot of context switches on linux

  - by Gaks

  According to vmstat, my Linux server (2xCore2 Duo 2.5 GHz) is constantly doing around 20k context switches per second. # vmstat 3 procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 2 0 7292 249472 82340 2291972 0 0 0 0 0 0 7 13 79 0 0 0 7292 251808 82344 2291968 0 0 0 184 24 20090 1 1 99 0 0 0 7292 251876 82344 2291968 0 0 0 83 17 20157 1 0 99 0 0 0 7292 251876 82344 2291968 0 0 0 73 12 20116 1 0 99 0 ... but uptime shows small load: load average: 0.01, 0.02, 0.01 and top doesn't show any process with high %CPU usage. How do I find out what exactly is generating those context switches? Which process/thread? I tried to analyze pidstat output: # pidstat -w 10 1 12:39:13 PID cswch/s nvcswch/s Command 12:39:23 1 0.20 0.00 init 12:39:23 4 0.20 0.00 ksoftirqd/0 12:39:23 7 1.60 0.00 events/0 12:39:23 8 1.50 0.00 events/1 12:39:23 89 0.50 0.00 kblockd/0 12:39:23 90 0.30 0.00 kblockd/1 12:39:23 995 0.40 0.00 kirqd 12:39:23 997 0.60 0.00 kjournald 12:39:23 1146 0.20 0.00 svscan 12:39:23 2162 5.00 0.00 kjournald 12:39:23 2526 0.20 2.00 postgres 12:39:23 2530 1.00 0.30 postgres 12:39:23 2534 5.00 3.20 postgres 12:39:23 2536 1.40 1.70 postgres 12:39:23 12061 10.59 0.90 postgres 12:39:23 14442 1.50 2.20 postgres 12:39:23 15416 0.20 0.00 monitor 12:39:23 17289 0.10 0.00 syslogd 12:39:23 21776 0.40 0.30 postgres 12:39:23 23638 0.10 0.00 screen 12:39:23 25153 1.00 0.00 sshd 12:39:23 25185 86.61 0.00 daemon1 12:39:23 25190 12.19 35.86 postgres 12:39:23 25295 2.00 0.00 screen 12:39:23 25743 9.99 0.00 daemon2 12:39:23 25747 1.10 3.00 postgres 12:39:23 26968 5.09 0.80 postgres 12:39:23 26969 5.00 0.00 postgres 12:39:23 26970 1.10 0.20 postgres 12:39:23 26971 17.98 1.80 postgres 12:39:23 27607 0.90 0.40 postgres 12:39:23 29338 4.30 0.00 screen 12:39:23 31247 4.10 23.58 postgres 12:39:23 31249 82.92 34.77 postgres 12:39:23 31484 0.20 0.00 pdflush 12:39:23 32097 0.10 0.00 pidstat Looks like some postgresql tasks are doing 10 context swiches per second, but it doesn't all sum up to 20k anyway. Any idea how to dig a little deeper for an answer?

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• Changing memory allocator to Jemalloc Centos 6

  - by Brian Lovett

  After reading this blog post about the impact of memory allocators like jemalloc on highly threaded applications, I wanted to test things on a larger scale on some of our cluster of servers. We run sphinx, and apache using threads, and on 24 core machines. Installing jemalloc was simple enough. We are running Centos 6, so yum install jemalloc jemalloc-devel did the trick. My question is, how do we change everything on the system over to using jemalloc instead of the default malloc built into Centos. Research pointed me at this as a potential option: LD_PRELOAD=$LD_PRELOAD:/usr/lib64/libjemalloc.so.1 Would this be sufficient to get everything using jemalloc?

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