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• Disk usage on IIS, PHP5, performance problems.

  - by Jacob84

  Hi everybody, I'm quite worried with a performance problem that I'm facing in one of our production servers. I'm working for a hosting company, so you can imagine how heterogeneous the applications runnning here are. All started with a call of a client complaining about the speed loading a Joomla. The setup is IIS6 (Windows 2003) with PHP5 and FAST CGI wich normally works pretty well. I've tested the loading time and indeed, he was right. 7 or 8 seconds to load, when usually this can be accomplished in 2. Seeing this results, I started to check first CPU and RAM. Everithing normal, 2GB of RAM free, 3%-8% of CPU activity. That's what I call a relaxed server ;). Unfortunately, digging a little deeper I've found the 'PhysicalDisk' counters quite high (above 10), specially the read queues. I've used Process Explorer to see wich of those processes has the higher deltas, but everything seemed normal. As the problem is specially related to PHP pages, I've checked specific IIS counters, as Actual connections, Number of CGI requeriments and Number of ISAPI requeriments. CGI -> 3 to 7 ISAPI -> 5 to 9 Connections-> 90 to 120 (wich appears at the top of the graph) More than a solution (I know this is hard to find), I would like to know if you have an specifical methodology to face this kind of problems. Thanks a lot, as always.

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• Photoshop CS5 performance over network drive (cifs)

  - by grub

  Hello Everyone I did install a QNAP NAS TS410 for a customer (professional photographer) with 3 Hitachi Deskstar 7200rpm 2TB disk configured as RAID5. The NAS and the workstations are connected over a Gigabit network. He and his co-worker are accessing the photos (about 1TB of photos) over a mapped network drive from their windows machines (Windows XP - 32bit and Windows 7 Ultimate - 32bit). Both are using Photoshop CS5 to edit the photos. The problem is that to save a edited photo takes a really long time, it takes about 3 times as long to save a photo as to open it. After some tests I can exclude the network, the NAS and the windows machines as source of the issue. I think the problem is the Photoshop software and its handling of the network drives. Officially network drives are not supported by Adobe. I do not have any experience with the Adobe products, especially with Adobe Photoshop CS5. What are your recommendation to solve the performance issue? Should my customer copy the photos to the local drive, edit them and upload them again to the network drive or is Adobe Drive or Adobe Version Cue the answer? One requirement is that the photos need to be accessible / editable from both computers even when one of them is offline. Adobe Version Cue needs a dedicated service running to be usable, so this solution is not possible as far as I understand the Cue software. Thank you for your input to this issue and have a nice day :-) Greetings grub

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• Performance decrease in every game and application

  - by Márk Vincze

  When I start a game, initially it runs smoothly, but after a couple of minutes, the performance gradually decreases to the point of being unplayable (1-2 FPS). The sound also starts to lag at this point. This does not happen every time I start my PC, usually exiting the game, rebooting, then starting the game again solves the problem, and I can play with perfect FPS for as long as I want. I could not find any deterministic reason when this happens and when doesn't. It happens in every game I tried (SWTOR, Diablo 3, Skyrim), and not even games, but simple applications like a browser or the Control Panel can get unusably slow. This is a brand new PC I bought three months ago, and this problem occurs since the first day I've been using it. Could you provide any advice how to further diagnose the problem? I tried to reinstall Windows, and tried different video card drivers, but it did not help. It would be important to know whether this is a hardware or software problem, because I can use the warranty if it is a hardware issue. (I did not want to return the PC yet, because I can't reproduce the issue deterministically.) Spec of the pc: Motherboard: ASROCK H61M-HVS CPU: INTEL Core i3-2120 3.30GHz 1155 BOX Memory: KINGMAX 4096MB DDR3 1333MHz KIT Video card: GIGABYTE GV-R685OC-1GD HD6850 1GB GDDR5 PCIE HDD: SEAGATE 500GB Barracuda 7200rpm 16MB SATA3 ST500DM002 I am using Windows 7 64 bit. Thanks a lot in advance!

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• Is there a word or description for this type of query?

  - by Nick

  We have the requirement to find a result in a collection of records based on a prioritised set of search criteria against a relational db (I'm talking indexed field matching here rather than text search). The way we are thinking about designing the query is to begin with a highly refined and specific set of criteria. If there are no results for this initial query we want to progressively reduce the criteria one by one in order of reducing priority, querying each time such a less specific set of criteria until we find a result we can accept. Alternatively, we have considered starting with a smaller set of criteria and increasing until we have reduced number of results down to the last set. What I would like to know is if an existing term to describe this type of query exists? So that we can look to model our own on existing patterns and use best practice.

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• file read performance degrades as number of files increases

  - by bfallik-bamboom

  We're observing poor file read IO results that we'd like to better understand. We can use fio to write 100 files with a sustained aggregate throughput of ~700MB/s. When we switch the test to read instead of write, the aggregate throughput is only ~55MB/s. The drop seems related to the number of files since the throughput for read and write are comparable for a single file then diverge proportionally as we increase the number of files. The test server has 24 CPU cores, 48GB of memory, and is running CentOS 6.0. The disk hardware is a RAID 6 array with 12 disks and a Dell H800 controller. This device is partitioned with ext4 using the default settings. Increasing the readahead (using blockdev) improves the read throughput significantly but it still doesn't match write speed. For instance, increasing the readahead from 128KB to 1M improved the read throughput to ~145MB/s. Is this a known performance issue in our OS/disk/filesystem configuration? If so, how can we tell? If not, what tools or tests can we use to further isolate the issue? Thanks.

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• SQL SERVER – SQL in Sixty Seconds – 5 Videos from Joes 2 Pros Series – SQL Exam Prep Series 70-433

  - by pinaldave

  Joes 2 Pros SQL Server Learning series is indeed fun. Joes 2 Pros series is written for beginners and who wants to build expertise for SQL Server programming and development from fundamental. In the beginning of the series author Rick Morelan is not shy to explain the simplest concept of how to open SQL Server Management Studio. Honestly the book starts with that much basic but as it progresses further Rick discussing about various advanced concepts from query tuning to Core Architecture. This five part series is written with keeping SQL Server Exam 70-433. Instead of just focusing on what will be there in exam, this series is focusing on learning the important concepts thoroughly. This book no way take short cut to explain any concepts and at times, will go beyond the topic at length. The best part is that all the books has many companion videos explaining the concepts and videos. Every Wednesday I like to post a video which explains something in quick few seconds. Today we will go over five videos which I posted in my earlier posts related to Joes 2 Pros series. Introduction to XML Data Type Methods – SQL in Sixty Seconds #015 The XML data type was first introduced with SQL Server 2005. This data type continues with SQL Server 2008 where expanded XML features are available, most notably is the power of the XQuery language to analyze and query the values contained in your XML instance. There are five XML data type methods available in SQL Server 2008: query() – Used to extract XML fragments from an XML data type. value() – Used to extract a single value from an XML document. exist() – Used to determine if a specified node exists. Returns 1 if yes and 0 if no. modify() – Updates XML data in an XML data type. node() – Shreds XML data into multiple rows (not covered in this blog post). [Detailed Blog Post] | [Quiz with Answer] Introduction to SQL Error Actions – SQL in Sixty Seconds #014 Most people believe that when SQL Server encounters an error severity level 11 or higher the remaining SQL statements will not get executed. In addition, people also believe that if any error severity level of 11 or higher is hit inside an explicit transaction, then the whole statement will fail as a unit. While both of these beliefs are true 99% of the time, they are not true in all cases. It is these outlying cases that frequently cause unexpected results in your SQL code. To understand how to achieve consistent results you need to know the four ways SQL Error Actions can react to error severity levels 11-16: Statement Termination – The statement with the procedure fails but the code keeps on running to the next statement. Transactions are not affected. Scope Abortion – The current procedure, function or batch is aborted and the next calling scope keeps running. That is, if Stored Procedure A calls B and C, and B fails, then nothing in B runs but A continues to call C. @@Error is set but the procedure does not have a return value. Batch Termination – The entire client call is terminated. XACT_ABORT – (ON = The entire client call is terminated.) or (OFF = SQL Server will choose how to handle all errors.) [Detailed Blog Post] | [Quiz with Answer] Introduction to Basics of a Query Hint – SQL in Sixty Seconds #013 Query hints specify that the indicated hints should be used throughout the query. Query hints affect all operators in the statement and are implemented using the OPTION clause. Cautionary Note: Because the SQL Server Query Optimizer typically selects the best execution plan for a query, it is highly recommended that hints be used as a last resort for experienced developers and database administrators to achieve the desired results. [Detailed Blog Post] | [Quiz with Answer] Introduction to Hierarchical Query – SQL in Sixty Seconds #012 A CTE can be thought of as a temporary result set and are similar to a derived table in that it is not stored as an object and lasts only for the duration of the query. A CTE is generally considered to be more readable than a derived table and does not require the extra effort of declaring a Temp Table while providing the same benefits to the user. However; a CTE is more powerful than a derived table as it can also be self-referencing, or even referenced multiple times in the same query. A recursive CTE requires four elements in order to work properly: Anchor query (runs once and the results ‘seed’ the Recursive query) Recursive query (runs multiple times and is the criteria for the remaining results) UNION ALL statement to bind the Anchor and Recursive queries together. INNER JOIN statement to bind the Recursive query to the results of the CTE. [Detailed Blog Post] | [Quiz with Answer] Introduction to SQL Server Security – SQL in Sixty Seconds #011 Let’s get some basic definitions down first. Take the workplace example where “Tom” needs “Read” access to the “Financial Folder”. What are the Securable, Principal, and Permissions from that last sentence? A Securable is a resource that someone might want to access (like the Financial Folder). A Principal is anything that might want to gain access to the securable (like Tom). A Permission is the level of access a principal has to a securable (like Read). [Detailed Blog Post] | [Quiz with Answer] Please leave a comment explain which one was your favorite video as that will help me understand what works and what needs improvement. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology, Video

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• Using Query Classes With NHibernate

  - by Liam McLennan

  Even when using an ORM, such as NHibernate, the developer still has to decide how to perform queries. The simplest strategy is to get access to an ISession and directly perform a query whenever you need data. The problem is that doing so spreads query logic throughout the entire application – a clear violation of the Single Responsibility Principle. A more advanced strategy is to use Eric Evan’s Repository pattern, thus isolating all query logic within the repository classes. I prefer to use Query Classes. Every query needed by the application is represented by a query class, aka a specification. To perform a query I: Instantiate a new instance of the required query class, providing any data that it needs Pass the instantiated query class to an extension method on NHibernate’s ISession type. To query my database for all people over the age of sixteen looks like this: [Test] public void QueryBySpecification() { var canDriveSpecification = new PeopleOverAgeSpecification(16); var allPeopleOfDrivingAge = session.QueryBySpecification(canDriveSpecification); } To be able to query for people over a certain age I had to create a suitable query class: public class PeopleOverAgeSpecification : Specification<Person> { private readonly int age; public PeopleOverAgeSpecification(int age) { this.age = age; } public override IQueryable<Person> Reduce(IQueryable<Person> collection) { return collection.Where(person => person.Age > age); } public override IQueryable<Person> Sort(IQueryable<Person> collection) { return collection.OrderBy(person => person.Name); } } Finally, the extension method to add QueryBySpecification to ISession: public static class SessionExtensions { public static IEnumerable<T> QueryBySpecification<T>(this ISession session, Specification<T> specification) { return specification.Fetch( specification.Sort( specification.Reduce(session.Query<T>()) ) ); } } The inspiration for this style of data access came from Ayende’s post Do You Need a Framework?. I am sick of working through multiple layers of abstraction that don’t do anything. Have you ever seen code that required a service layer to call a method on a repository, that delegated to a common repository base class that wrapped and ORMs unit of work? I can achieve the same thing with NHibernate’s ISession and a single extension method. If you’re interested you can get the full Query Classes example source from Github.

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• VMWare Esxi Looking for Bottlenecks

  - by nextgenneo

  I have a VMWare ESxi box, 22GB ram, Dual Quad Core Xeon, 2 Sas drives + Write caching raid controller etc. Anyways, have about 30 small XP VM's running on it and starting to get some very slow boot times and other performance issues. I THINK its I/O but looking at the graphs not too sure what to look for. Any ideas on what to look for would be appreciated. Here is the data I've got so far: (I feel like my IO is high but not sure what to bench it against)

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• Is it OK to run perfmon on production servers? And why?

  - by Bill Paetzke

  Or should perfmon be limited to a Dev/QA server with load tests that simulate production activity? I'd like to run perfmon for a two days (like Sql Server master Brent Ozar suggests) to get an overall feel of my web app's database performance.

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• IIS/ASP.NET performance incident - Perfmon Current Annonymous Users going through roof but Requests/sec low

  - by Laurence

  Setup: ASP.NET 4.0 website on IIS 6.0 on Win 2003 64 bit, 8xCPUs, 16GB memory, separate SQL 2005 DB server. Had a serious slowdown today with any otherwise fairly well performing ASP.NET site. For a period of a couple of hours all page requests were taking a very long time to be served - e.g. 30-60s compared to usual 2s. The w3wp.exe's CPU and memory usage on the webserver was not much higher than normal. The application pool was not in the middle of recycling (and it hadn't recycled for several hours). Bottlenecks in the database were ruled out - no blocks occurring and query results were being returned quickly. I couldn't make any sense of it and set up the following Perfmon counters: Current Anonymous Users (for site in question) Get requests/sec (ditto) Requests/sec for the ASP.NET application running the site Get requests/sec was averaging 100-150. Requests/sec for ASP.NET was averaging 5-10. However Current Anonymous Users was around 200. And then as I was watching, the Current Anonymous Users began to climb steeply going up to about 500 within a few minutes. All this time Get requests/sec & Requests/sec for ASP.NET was if anything going down. I did a whole load of things (in a panic!) to try to get the site working, like shutting it down, recycling the app pool, and adding another worker process to the pool. I also extended the expiration time for content (in IIS under HTTP Headers) in an attempt to lower the number of requests for static files (there are a lot of images on the site). The site is now back to normal, and the counters are fairly steady and reading (added Current Connections counter): Current Anonymous Users : average 30 Get requests/sec : average 100 Requests/sec for ASP.NET : 5 Current Connections : average 300 I have also observed an inverse relationship between Get requests/sec & Current Anonymous Users. Usually both are fairly steady but there will be short periods when Get requests/sec will go down dramatically and Current Anonymous Users will go up in a perfect mirror image. Then they will flip back to their usual levels. So, my questions are: Thinking of the original performance issue - if w3wp.exe CPU, memory usage were normal and there was no DB bottleneck, what could explain page requests taking 20 times longer to be served than usual? What other counters should I be looking at if this happens again? What explains the inverse relationship between Get requests/sec & Current Anonymous Users? What could explain Current Anonymous Users going from 200 to 500 within a few minutes? Many thanks for any insight into this.

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• Baseline / Benchmark Physical and virtual server performance

  - by EyeonTech

  I am setting up a new server and there are some options. I want to perform some benchmarks and I need your help in determining the best tools and if possible run pre-configured benchmarks designed for SQL servers on Windows Server 2008/2012. Step 1. Run a performance monitor on the current Live SQL server (Windows Server 2008 Virtual machine running on ESXi. New server Hardware rundown: Intel® Server System R1304BTLSHBN - 1U Rack, LGA1155 http://ark.intel.com/products/53559/Intel-Server-System-R1304BTLSHBN Intel Xeon E3-1270V2 2x Intel SSD 330 Series 240GB 2.5in SATA 6Gb/s 25nm 1x WD 2TB WD2002FAEX 2TB 64M SATA3 CAVIAR BLACK 4x 8GB 1333MHz DDR3 ECC CL9 DIMM There are several options for configurations and I want to benchmark some of them and share the results. Option 1. Configure 2x SSDs at RAID 0. Install Windows Server 2008 directly to the 2TB WD Caviar HDD. Store Database files on the RAID 0 Volume. Benchmark the OS direct on the hardware as an SQL Server. Store SQL Backup databases on the 2TB WD Caviar HDD. Option 2. Configure 2x SSDs at RAID 0. Install Windows Server 2012 directly to the 2TB WD Caviar HDD. Install Hyper-V. Install the SQL Server (Server 2008) as a virtual machine. Store the Virtual Hard Disks on the SSDs. Option 3. Configure 2x SSDs at RAID 0. Install VMWare ESXi on a partition of the 2TB WD Caviar HDD. Install the SQL Server (Server 2008) as a virtual machine. Store the Virtual Hard Disks on the SSDs. I have a few tools in mind from http://technet.microsoft.com/en-us/library/cc768530(v=bts.10).aspx. Any tools with pre-configured test would be fantastic. Specifically if there are pre-configured perfmon sets avaliable. Any opinions on the setup to gain the best results is welcome. Thanks in advance.

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• bind would not work unless allow-query is "any"

  - by adrianTNT

  I have this in /etc/named.conf, I commented the default values and set my own under it. My domain would not load in browser unless I set allow-query to "any", is this OK, what should I edit? If is localhost or 127.0.0.1; 10.0.1.0/24; domain would not load. I tried the 127.. thing because it mentioned it here: http://wiki.mandriva.com/en/Testing:Bind Bind version is 9.7.0-P2-RedHat-9.7.0-5.P2.el6_0.1 OS is CentOS 6.0. options { // listen-on port 53 { 127.0.0.1; }; listen-on port 53 { any; }; //listen-on-v6 port 53 { ::1; }; listen-on-v6 port 53 { any; }; directory "/var/named"; dump-file "/var/named/data/cache_dump.db"; statistics-file "/var/named/data/named_stats.txt"; memstatistics-file "/var/named/data/named_mem_stats.txt"; //allow-query { localhost; }; allow-query { any; }; recursion yes; dnssec-enable yes; dnssec-validation yes; dnssec-lookaside auto; /* Path to ISC DLV key */ bindkeys-file "/etc/named.iscdlv.key"; };

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• MySQL query cache and PHP variables

  - by Saif Bechan

  I have seen the following statement made about the query cache: // query cache does NOT work $r = mysql_query("SELECT username FROM user WHERE signup_date >= CURDATE()"); // query cache works! $today = date("Y-m-d"); $r = mysql_query("SELECT username FROM user WHERE signup_date >= '$today'"); So the query cache only works on the second query. I was wondering if the query cache will also work on this: define('__TODAY',date("Y-m-d")); $r = mysql_query("SELECT username FROM user WHERE signup_date >= '".__TODAY."'");

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• ADO.NET Commands and SQL query plans

  - by ingredient_15939

  I've been reading up on query plans and how to minimise duplicate plans being created by SQL Server for the same basic query. For example, if I understand correctly, sending both these query strings will result in 2 different query plans: "SELECT FirstName FROM Members WHERE LastName = 'Lee'" "SELECT FirstName FROM Members WHERE LastName = 'MacGhilleseatheanaich'" Using a stored procedure avoids this, as the query plan is the same, and "LastName" is passed as a variable, eg: CREATE PROCEDURE sp_myStoredProcedure @LastName varchar(100) AS SELECT FirstName FROM Members WHERE LastName = @LastName Go Now, my question is whether the same applies to the Command object (eg. SQLClient.SQLCommand in ADO.NET). The reason I ask is that string parameters don't have a defined max length, as in the code above. Take the following code: MyCmd.CommandText = "SELECT FirstName FROM Members WHERE LastName = @LastName" MyCmd.Parameters.AddWithValue("@LastName", "Lee") Then later: MyCmd.Parameters.Clear() MyCmd.Parameters.AddWithValue("@LastName", "MacGhilleseatheanaich") Since @LastName hasn't been declared to SQL Server as having a defined maximum length, will SQL Server create a new query plan for every different value when I execute the command this way?

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• rewritten mysql query returning unexpected results, trying to figure out why

  - by dq

  I created a messy query in a hurry a while ago to get a list of product codes. I am now trying to clean up my tables and my code. I recently tried to rewrite the query in order for it to be easier to use and understand. The original query works great, but it requires multiple search strings in order to do one search because it uses UNIONS, and it has a few other issues. My newly modified query is easier to understand, and only requires one search string, but is returning different results. Basically the new query is leaving records out, and I would like to understand why, and how to fix it. Here are the two queries (search strings are all null): Original Query: $query = 'SELECT product_code FROM bus_warehouse_lots WHERE status=\'2\''.$search_string_1 .' UNION SELECT product_code FROM bus_po WHERE status=\'0\''.$search_string_2 .' UNION SELECT bus_warehouse_entries.new_product_code AS product_code FROM (bus_warehouse_entries LEFT JOIN bus_warehouse_transfers ON bus_warehouse_entries.picking_ticket_num=bus_warehouse_transfers.pt_number) LEFT JOIN bus_warehouse_lots ON bus_warehouse_entries.ebooks_lot_id=bus_warehouse_lots.id WHERE bus_warehouse_entries.type=\'6\' AND bus_warehouse_transfers.status=\'0\''.$search_string_3 .' UNION SELECT bus_contracts.main_product AS product_code FROM bus_contracts LEFT JOIN bus_warehouse_lots ON bus_contracts.main_product=bus_warehouse_lots.product_code WHERE bus_contracts.status=\'0\''.$search_string_4 .' UNION SELECT prod_id AS product_code FROM bus_products WHERE last_usage > \''.date('Y-m-d', strtotime('-12 months')).'\''.$search_string_5 .' ORDER BY product_code'; New Query: $query = 'SELECT bus_products.prod_id FROM bus_products' .' LEFT JOIN (bus_warehouse_lots, bus_po, bus_warehouse_entries, bus_contracts) ON (' .'bus_products.prod_id = bus_warehouse_lots.product_code' .' AND bus_products.prod_id = bus_po.product_code' .' AND bus_products.prod_id = bus_warehouse_entries.new_product_code' .' AND bus_products.prod_id = bus_contracts.main_product)' .' LEFT JOIN bus_warehouse_transfers ON' .' bus_warehouse_entries.picking_ticket_num = bus_warehouse_transfers.pt_number' .' WHERE (bus_products.last_usage > \''.date('Y-m-d', strtotime('-12 months')).'\'' .' OR bus_warehouse_lots.status = \'2\'' .' OR bus_po.status = \'0\'' .' OR (bus_warehouse_entries.type = \'6\' AND bus_warehouse_transfers.status = \'0\')' .' OR bus_contracts.status = \'0\')' .$search_string_6 .' GROUP BY bus_products.prod_id' .' ORDER BY bus_products.prod_id';

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• SQL query duration is longer for smaller dataset?

  - by entens

  I received reports that a my report generating application was not working. After my initial investigation, I found that the SQL transaction was timing out. I'm mystified as to why the query for a smaller selection of items would take so much longer to return results. Quick query (averages 4 seconds to return): SELECT * FROM Payroll WHERE LINEDATE >= '04-17-2010'AND LINEDATE <= '04-24-2010' ORDER BY 'EMPLYEE_NUM' ASC, 'OP_CODE' ASC, 'LINEDATE' ASC Long query (averages 1 minute 20 seconds to return): SELECT * FROM Payroll WHERE LINEDATE >= '04-18-2010'AND LINEDATE <= '04-24-2010' ORDER BY 'EMPLYEE_NUM' ASC, 'OP_CODE' ASC, 'LINEDATE' ASC I could simply increase the timeout on the SqlCommand, but it doesn't change the fact the query is taking longer than it should. Why would requesting a subset of the items take longer than the query that returns more data? How can I optimize this query?

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• Performance Tuning a High-Load Apache Server

  - by futureal

  I am looking to understand some server performance problems I am seeing with a (for us) heavily loaded web server. The environment is as follows: Debian Lenny (all stable packages + patched to security updates) Apache 2.2.9 PHP 5.2.6 Amazon EC2 large instance The behavior we're seeing is that the web typically feels responsive, but with a slight delay to begin handling a request -- sometimes a fraction of a second, sometimes 2-3 seconds in our peak usage times. The actual load on the server is being reported as very high -- often 10.xx or 20.xx as reported by top. Further, running other things on the server during these times (even vi) is very slow, so the load is definitely up there. Oddly enough Apache remains very responsive, other than that initial delay. We have Apache configured as follows, using prefork: StartServers 5 MinSpareServers 5 MaxSpareServers 10 MaxClients 150 MaxRequestsPerChild 0 And KeepAlive as: KeepAlive On MaxKeepAliveRequests 100 KeepAliveTimeout 5 Looking at the server-status page, even at these times of heavy load we are rarely hitting the client cap, usually serving between 80-100 requests and many of those in the keepalive state. That tells me to rule out the initial request slowness as "waiting for a handler" but I may be wrong. Amazon's CloudWatch monitoring tells me that even when our OS is reporting a load of 15, our instance CPU utilization is between 75-80%. Example output from top: top - 15:47:06 up 31 days, 1:38, 8 users, load average: 11.46, 7.10, 6.56 Tasks: 221 total, 28 running, 193 sleeping, 0 stopped, 0 zombie Cpu(s): 66.9%us, 22.1%sy, 0.0%ni, 2.6%id, 3.1%wa, 0.0%hi, 0.7%si, 4.5%st Mem: 7871900k total, 7850624k used, 21276k free, 68728k buffers Swap: 0k total, 0k used, 0k free, 3750664k cached The majority of the processes look like: 24720 www-data 15 0 202m 26m 4412 S 9 0.3 0:02.97 apache2 24530 www-data 15 0 212m 35m 4544 S 7 0.5 0:03.05 apache2 24846 www-data 15 0 209m 33m 4420 S 7 0.4 0:01.03 apache2 24083 www-data 15 0 211m 35m 4484 S 7 0.5 0:07.14 apache2 24615 www-data 15 0 212m 35m 4404 S 7 0.5 0:02.89 apache2 Example output from vmstat at the same time as the above: procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 8 0 0 215084 68908 3774864 0 0 154 228 5 7 32 12 42 9 6 21 0 198948 68936 3775740 0 0 676 2363 4022 1047 56 16 9 15 23 0 0 169460 68936 3776356 0 0 432 1372 3762 835 76 21 0 0 23 1 0 140412 68936 3776648 0 0 280 0 3157 827 70 25 0 0 20 1 0 115892 68936 3776792 0 0 188 8 2802 532 68 24 0 0 6 1 0 133368 68936 3777780 0 0 752 71 3501 878 67 29 0 1 0 1 0 146656 68944 3778064 0 0 308 2052 3312 850 38 17 19 24 2 0 0 202104 68952 3778140 0 0 28 90 2617 700 44 13 33 5 9 0 0 188960 68956 3778200 0 0 8 0 2226 475 59 17 6 2 3 0 0 166364 68956 3778252 0 0 0 21 2288 386 65 19 1 0 And finally, output from Apache's server-status: Server uptime: 31 days 2 hours 18 minutes 31 seconds Total accesses: 60102946 - Total Traffic: 974.5 GB CPU Usage: u209.62 s75.19 cu0 cs0 - .0106% CPU load 22.4 requests/sec - 380.3 kB/second - 17.0 kB/request 107 requests currently being processed, 6 idle workers C.KKKW..KWWKKWKW.KKKCKK..KKK.KKKK.KK._WK.K.K.KKKKK.K.R.KK..C.C.K K.C.K..WK_K..KKW_CK.WK..W.KKKWKCKCKW.W_KKKKK.KKWKKKW._KKK.CKK... KK_KWKKKWKCKCWKK.KKKCK.......................................... ................................................................ From my limited experience I draw the following conclusions/questions: We may be allowing far too many KeepAlive requests I do see some time spent waiting for IO in the vmstat although not consistently and not a lot (I think?) so I am not sure this is a big concern or not, I am less experienced with vmstat Also in vmstat, I see in some iterations a number of processes waiting to be served, which is what I am attributing the initial page load delay on our web server to, possibly erroneously We serve a mixture of static content (75% or higher) and script content, and the script content is often fairly processor intensive, so finding the right balance between the two is important; long term we want to move statics elsewhere to optimize both servers but our software is not ready for that today I am happy to provide additional information if anybody has any ideas, the other note is that this is a high-availability production installation so I am wary of making tweak after tweak, and is why I haven't played with things like the KeepAlive value myself yet.

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• Too many Bind query (cache) denied, DNS attack?

  - by Jake

  Once Bind crashed and I did: tail -f /var/log/messages I see a massive number of logs every second. Is this a DNS attack? or is there something wrong? Sometimes I see a domain in logs like this: dOmAin.com (upper and lower). As you see there is only one single domain in the logs with different IPs Oct 10 02:21:26 mail named[20831]: client 74.125.189.18#38921: query (cache) 'ns1.domain2.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 192.221.144.171#38833: query (cache) 'domain.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 74.125.189.17#42428: query (cache) 'ns2.domain2.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 192.221.146.27#37899: query (cache) 'domain.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 193.203.82.66#39263: query (cache) 'domain.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 8.0.16.170#59723: query (cache) 'domain.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 80.169.197.66#32903: query (cache) 'dOmAin.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 134.58.60.1#47558: query (cache) 'domain.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 192.221.146.34#47387: query (cache) 'domain.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 8.0.16.8#59392: query (cache) 'domain.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 74.125.189.19#64395: query (cache) 'domain.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 217.72.163.3#42190: query (cache) 'domain.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 83.146.21.252#22020: query (cache) 'domain.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 192.221.146.116#57342: query (cache) 'domain.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 193.203.82.66#52020: query (cache) 'domain.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 8.0.16.72#64317: query (cache) 'domain.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 80.169.197.66#31989: query (cache) 'dOmAin.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 74.125.189.18#47436: query (cache) 'ns2.domain2.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 74.125.189.16#44005: query (cache) 'ns1.domain2.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 85.132.31.10#50379: query (cache) 'domain.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 94.241.128.3#60106: query (cache) 'domain.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 85.132.31.10#59118: query (cache) 'domain.com/A/IN' denied Oct 10 02:21:26 mail named[20831]: client 212.95.135.78#27811: query (cache) 'domain.com/A/IN' denied /etc/resolv.conf ; generated by /sbin/dhclient-script nameserver 4.2.2.4 nameserver 8.8.4.4 Bind config: // generated by named-bootconf.pl options { directory "/var/named"; /* * If there is a firewall between you and nameservers you want * to talk to, you might need to uncomment the query-source * directive below. Previous versions of BIND always asked * questions using port 53, but BIND 8.1 uses an unprivileged * port by default. */ // query-source address * port 53; allow-transfer { none; }; allow-recursion { localnets; }; //listen-on-v6 { any; }; notify no; }; // // a caching only nameserver config // controls { inet 127.0.0.1 allow { localhost; } keys { rndckey; }; }; zone "." IN { type hint; file "named.ca"; }; zone "localhost" IN { type master; file "localhost.zone"; allow-update { none; }; }; zone "0.0.127.in-addr.arpa" IN { type master; file "named.local"; allow-update { none; }; };

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• What is recommended minimum object size for gzip performance benefits?

  - by utt73

  I'm working on improving page speed display times, and one of the methods is to gzip content from the webserver. Google recommends: Note that gzipping is only beneficial for larger resources. Due to the overhead and latency of compression and decompression, you should only gzip files above a certain size threshold; we recommend a minimum range between 150 and 1000 bytes. Gzipping files below 150 bytes can actually make them larger. We serve our content through Akamai, using their network for a proxy and CDN. What they've told me: Following up on your question regarding what is the minimum size Akamai will compress the requested object when sending it to the end user: The minimum size is 860 bytes. My reply: What is the reason(s) for why Akamai's minimum size is 860 bytes? And why, for example, is this not the case for files Akamai serves for facebook? (see below) Google recommends to gzip more agressively. And that seems appropriate on our site where the most frequent hits, by far, are AJAX calls that are <860 bytes. Akamai's response: The reasons 860 bytes is the minimum size for compression is twofold: (1) The overhead of compressing an object under 860 bytes outweighs performance gain. (2) Objects under 860 bytes can be transmitted via a single packet anyway, so there isn't a compelling reason to compress them. So I'm here for some fact checking. Is the 860 byte limit due to packet size the end of this reasoning? Why would high traffic sites push this down to the 150 byte limit... just to save on bandwidth costs (since CDNs base their charges on bandwith offloaded from origin), or is there a performance gain in doing so?

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• How do I measure performance of a virtual server?

  - by Sergey

  I've got a VPS running Ubuntu. Being a virtual server, I understand that it shares resources with unknown number of other servers, and I'm noticing that it's considerably slower than my desktop machine. Is there some tool to measure the performance of the virtual machine? I'd be curious to see some approximate measure similar to bogomips, possibly for CPU (operations/sec), memory and disk read/write speed. I'd like to be able to compare those numbers to my desktop machine. I'm not interested in the specs of the actual physical machine my VPS is running on - by doing cat /proc/cpuinfo I can see that it's a nice quad-core Xeon machine, but it doesn't matter to me. I'm basically interested in how fast a program would run in my VPS - how many CPU operations it can make in a second, how many bytes to write to RAM or to disk. I only have ssh access to the machine so the tool need to be command-line. I could write a script which, say, does some calculations in a loop for a second and counts how many loops it was able to do, or something similar to measure disk and RAM performance. But I'm sure something like this already exists.

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• mysql partitioning

  - by Yang

  just want to verify that database partition is implemented only at the database level, when we query a partitioned table, we still do our normal query, nothing special with our queries, the optimization is performed automatically when parsing the query, is that correct? e.g. we have a table called 'address' with a column called 'country_code' and 'city'. so if i want to get all the addresses in New York, US, normally i wound do something like this: select * from address where country_code = 'US' and city = 'New York' if now the table is partitioned by 'country_code', and i know that now the query will only be executed on the partition which contains country_code = US. My question is do I need to explicitly specify the partition to query in my sql statement? or i still use the previous statement and the db server will optimize it automatically? Thanks in advance!

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• Performing client-side OAuth authorized Twitter API calls versus server side, how much of a difference is there in terms of performance?

  - by Terence Ponce

  I'm working on a Twitter application in Ruby on Rails. One of the biggest arguments that I have with other people on the project is the method of calling the Twitter API. Before, everything was done on the server: OAuth login, updating the user's Twitter data, and retrieving tweets. Retrieving tweets was the heaviest thing to do since we don't store the tweets in our database, so viewing the tweets means that we have to call the API every time. One of the people in the project suggested that we call the tweets through Javascript instead to lessen the load on the server. We used GET search, which, correct me if I'm wrong, will be removed when v1.0 becomes completely deprecated, but that really isn't a concern now. When the Twitter API has migrated completely to v1.1 (again, correct me if I'm wrong), every calls to the API must be authenticated, so we have to authenticate our Javascript requests to the API. As said here: We don't support or recommend performing OAuth directly through Javascript -- it's insecure and puts your application at risk. The only acceptable way to perform it is if you kept all keys and secrets server-side, computed the OAuth signatures and parameters server side, then issued the request client-side from the server-generated OAuth values. If we do exactly what Twitter suggests, the only difference between this and doing everything server-side is that our server won't have to contact the Twitter API anymore every time the user wants to view tweets. Here's how I would picture what's happening every time the user makes a request: If we do it through Javascript, it would be harder on my part because I would have to create the signatures manually for every request, but I will gladly do it if the boost in performance is worth all the trouble. Doing it through Ruby on Rails would be very easy since the Twitter gem does most of the grunt work already, so I'm really encouraging the other people in the project to agree with me. Is the difference in performance trivial or is it significant enough to switch to Javascript?

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• How to squeeze the maximum performance out of Unity and GNOME 3?

  - by melvincv

  I see that I do not get good performance with the new Unity desktop, but I should say that Unity has improved a lot since the last edition Ubuntu 11.10. How to squeeze the maximum performance out of 1. Unity 2. GNOME 3 My system specs: -Processors- Intel(R) Pentium(R) Dual CPU E2180 @ 2.00GHz -Memory- Total Memory : 2049996 kB -PCI Devices- Host bridge : Intel Corporation 82G33/G31/P35/P31 Express DRAM Controller (rev 10) PCI bridge : Intel Corporation 82G33/G31/P35/P31 Express PCI Express Root Port (rev 10) (prog-if 00 [Normal decode]) VGA compatible controller : Intel Corporation 82G33/G31 Express Integrated Graphics Controller (rev 10) (prog-if 00 [VGA controller]) USB controller : Intel Corporation N10/ICH 7 Family USB UHCI Controller #1 (rev 01) (prog-if 00 [UHCI]) USB controller : Intel Corporation N10/ICH 7 Family USB UHCI Controller #2 (rev 01) (prog-if 00 [UHCI]) USB controller : Intel Corporation N10/ICH 7 Family USB UHCI Controller #3 (rev 01) (prog-if 00 [UHCI]) USB controller : Intel Corporation N10/ICH 7 Family USB UHCI Controller #4 (rev 01) (prog-if 00 [UHCI]) USB controller : Intel Corporation N10/ICH 7 Family USB2 EHCI Controller (rev 01) (prog-if 20 [EHCI]) PCI bridge : Intel Corporation 82801 PCI Bridge (rev e1) (prog-if 01 [Subtractive decode]) ISA bridge : Intel Corporation 82801GB/GR (ICH7 Family) LPC Interface Bridge (rev 01) IDE interface : Intel Corporation 82801G (ICH7 Family) IDE Controller (rev 01) (prog-if 8a [Master SecP PriP]) IDE interface : Intel Corporation N10/ICH7 Family SATA Controller [IDE mode] (rev 01) (prog-if 8f [Master SecP SecO PriP PriO]) SMBus : Intel Corporation N10/ICH 7 Family SMBus Controller (rev 01) Ethernet controller : Intel Corporation PRO/100 VE Network Connection (rev 01)

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• Premature-Optimization and Performance Anxiety

  - by James Michael Hare

  While writing my post analyzing the new .NET 4 ConcurrentDictionary class (here), I fell into one of the classic blunders that I myself always love to warn about.  After analyzing the differences of time between a Dictionary with locking versus the new ConcurrentDictionary class, I noted that the ConcurrentDictionary was faster with read-heavy multi-threaded operations.  Then, I made the classic blunder of thinking that because the original Dictionary with locking was faster for those write-heavy uses, it was the best choice for those types of tasks.  In short, I fell into the premature-optimization anti-pattern. Basically, the premature-optimization anti-pattern is when a developer is coding very early for a perceived (whether rightly-or-wrongly) performance gain and sacrificing good design and maintainability in the process.  At best, the performance gains are usually negligible and at worst, can either negatively impact performance, or can degrade maintainability so much that time to market suffers or the code becomes very fragile due to the complexity. Keep in mind the distinction above.  I'm not talking about valid performance decisions.  There are decisions one should make when designing and writing an application that are valid performance decisions.  Examples of this are knowing the best data structures for a given situation (Dictionary versus List, for example) and choosing performance algorithms (linear search vs. binary search).  But these in my mind are macro optimizations.  The error is not in deciding to use a better data structure or algorithm, the anti-pattern as stated above is when you attempt to over-optimize early on in such a way that it sacrifices maintainability. In my case, I was actually considering trading the safety and maintainability gains of the ConcurrentDictionary (no locking required) for a slight performance gain by using the Dictionary with locking.  This would have been a mistake as I would be trading maintainability (ConcurrentDictionary requires no locking which helps readability) and safety (ConcurrentDictionary is safe for iteration even while being modified and you don't risk the developer locking incorrectly) -- and I fell for it even when I knew to watch out for it.  I think in my case, and it may be true for others as well, a large part of it was due to the time I was trained as a developer.  I began college in in the 90s when C and C++ was king and hardware speed and memory were still relatively priceless commodities and not to be squandered.  In those days, using a long instead of a short could waste precious resources, and as such, we were taught to try to minimize space and favor performance.  This is why in many cases such early code-bases were very hard to maintain.  I don't know how many times I heard back then to avoid too many function calls because of the overhead -- and in fact just last year I heard a new hire in the company where I work declare that she didn't want to refactor a long method because of function call overhead.  Now back then, that may have been a valid concern, but with today's modern hardware even if you're calling a trivial method in an extremely tight loop (which chances are the JIT compiler would optimize anyway) the results of removing method calls to speed up performance are negligible for the great majority of applications.  Now, obviously, there are those coding applications where speed is absolutely king (for example drivers, computer games, operating systems) where such sacrifices may be made.  But I would strongly advice against such optimization because of it's cost.  Many folks that are performing an optimization think it's always a win-win.  That they're simply adding speed to the application, what could possibly be wrong with that?  What they don't realize is the cost of their choice.  For every piece of straight-forward code that you obfuscate with performance enhancements, you risk the introduction of bugs in the long term technical debt of the application.  It will become so fragile over time that maintenance will become a nightmare.  I've seen such applications in places I have worked.  There are times I've seen applications where the designer was so obsessed with performance that they even designed their own memory management system for their application to try to squeeze out every ounce of performance.  Unfortunately, the application stability often suffers as a result and it is very difficult for anyone other than the original designer to maintain. I've even seen this recently where I heard a C++ developer bemoaning that in VS2010 the iterators are about twice as slow as they used to be because Microsoft added range checking (probably as part of the 0x standard implementation).  To me this was almost a joke.  Twice as slow sounds bad, but it almost never as bad as you think -- especially if you're gaining safety.  The only time twice is really that much slower is when once was too slow to begin with.  Think about it.  2 minutes is slow as a response time because 1 minute is slow.  But if an iterator takes 1 microsecond to move one position and a new, safer iterator takes 2 microseconds, this is trivial!  The only way you'd ever really notice this would be in iterating a collection just for the sake of iterating (i.e. no other operations).  To my mind, the added safety makes the extra time worth it. Always favor safety and maintainability when you can.  I know it can be a hard habit to break, especially if you started out your career early or in a language such as C where they are very performance conscious.  But in reality, these type of micro-optimizations only end up hurting you in the long run. Remember the two laws of optimization.  I'm not sure where I first heard these, but they are so true: For beginners: Do not optimize. For experts: Do not optimize yet. This is so true.  If you're a beginner, resist the urge to optimize at all costs.  And if you are an expert, delay that decision.  As long as you have chosen the right data structures and algorithms for your task, your performance will probably be more than sufficient.  Chances are it will be network, database, or disk hits that will be your slow-down, not your code.  As they say, 98% of your code's bottleneck is in 2% of your code so premature-optimization may add maintenance and safety debt that won't have any measurable impact.  Instead, code for maintainability and safety, and then, and only then, when you find a true bottleneck, then you should go back and optimize further.

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• MySQL performance - 100Mb ethernet vs 1Gb ethernet

  - by Rob Penridge

  Hi All I've just started a new job and noticed that the analysts computers are connected to the network at 100Mbps. The ODBC queries we run against the MySQL server can easily return 500MB+ and it seems at times when the servers are under high load the DBAs kill low priority jobs as they are taking too long to run. My question is this... How much of this server time is spent executing the request, and how much time is spent returning the data to the client? Could the query speeds be improved by upgrading the network connections to 1Gbps? (Updated for the why): The database in question was built to accomodate reporting needs and contains massive amounts of data. We usually work with subsets of this data at a granular level in external applications such as SAS or Excel, hence the reason for the large amounts of data being transmitted. The queries are not poorly structured - they are very simple and the appropriate joins/indexes etc are being used. I've removed 'query' from the Title of the post as I realised this question is more to do with general MySQL performance rather than query related performance. I was kind of hoping that someone with a Gigabit connection may be able to actually quantify some results for me here by running a query that returns a decent amount of data, then they could limit their connection speed to 100Mb and rerun the same query. Hopefully this could be done in an environment where loads are reasonably stable so as not to skew the results. If ethernet speed can improve the situation I wanted some quantifiable results to help argue my case for upgrading the network connections. Thanks Rob

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