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• Figuring out the Nyquist performance limitation of an ADC on an example PIC microcontroller

  - by AKE

  I'm spec-ing the suitability of a dsPIC microcontroller for an analog-to-digital application. This would be preferable to using dedicated A/D chips and a separate dedicated DSP chip. To do that, I've had to run through some computations, pulling the relevant parameters from the datasheets. I'm not sure I've got it right -- would appreciate a check! (EDITED NOTE: The PIC10F220 in the example below was selected ONLY to walk through a simple example to check that I'm interpreting Tacq, Fosc, TAD, and divisor correctly in working through this sort of Nyquist analysis. The actual chips I'm considering for the design are the dsPIC33FJ128MC804 (with 16b A/D) or dsPIC30F3014 (with 12b A/D).) A simple example: PIC10F220 is the simplest possible PIC with an ADC Runs at clock speed of 8MHz. Has an instruction cycle of 0.5us (4 clock steps per instruction) So: Taking Tacq = 6.06 us (acquisition time for ADC, assume chip temp. = 50*C) [datasheet p34] Taking Fosc = 8MHz (? clock speed) Taking divisor = 4 (4 clock steps per CPU instruction) This gives TAD = 0.5us (TAD = 1/(Fosc/divisor) ) Conversion time is 13*TAD [datasheet p31] This gives conversion time 6.5us ADC duration is then 12.56 us [? Tacq + 13*TAD] Assuming at least 2 instructions for load/store: This is another 1 us [0.5 us per instruction] Which would give max sampling rate of 73.7 ksps (1/13.56) Supposing 8 more instructions for real-time processing: This is another 4 us Thus, total ADC/handling time = 17.56us (12.56us + 1us + 4us) So expected upper sampling rate is 56.9 ksps. Nyquist frequency for this sampling rate is therefore 28 kHz. If this is right, it suggests the (theoretical) performance suitability of this chip's A/D is for signals that are bandlimited to 28 kHz. Is this a correct interpretation of the information given in the data sheet in obtaining the Nyquist performance limit? Any opinions on the noise susceptibility of ADCs in PIC / dsPIC chips would be much appreciated! AKE

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• Improving the performance of XSL

  - by Rachel

  I am using the below XSL 2.0 code to find the ids of the text nodes that contains the list of indices that i give as input. the code works perfectly but in terms for performance it is taking a long time for huge files. Even for huge files if the index values are small then the result is quick in few ms. I am using saxon9he Java processor to execute the XSL. <xsl:variable name="insert-data" as="element(data)*"> <xsl:for-each-group select="doc($insert-file)/insert-data/data" group-by="xsd:integer(@index)"> <xsl:sort select="current-grouping-key()"/> <data index="{current-grouping-key()}" text-id="{generate-id( $main-root/descendant::text()[ sum((preceding::text(), .)/string-length(.)) ge current-grouping-key() ][1] )}"> <xsl:copy-of select="current-group()/node()"/> </data> </xsl:for-each-group> </xsl:variable> In the above solution if the index value is too huge say 270962 then the time taken for the XSL to execute is 83427ms. In huge files if the index value is huge say 4605415, 4605431 it takes several minutes to execute. Seems the computation of the variable "insert-data" takes time though it is a global variable and computed only once. Should the XSL be addessed or the processor? How can i improve the performance of the XSL.

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• APplication performance issue : SqlServer & Oracle

  - by Mahesh

  Hi, We have a applicaiton in Silverlight,WCF, NHibernate. Currently it is supporting SQL Serve and Oracle database. As it's huge data, it is running ok on SQL Sevrer. But on Oracle it is running very slow. For one functionality it takes 5 Sec to execute on SQL Server and 30 Sec on Oracle. I am not able to figure out what will be issue. Two things that i want to share with you about our database. 1) Database: contains one base table contains column of type SQLServer: [Text] Oracle: [NCLOB] 2) Our database structure is too much normalized. May be in the oracle i have used NCLOB, that is the cause of the performance. I mean i don't know the details about it.... Can anyone please let me know what will be cause? Or Which actions do i need to follw to improve the performance as equal as SqlServer.? Thanks in advance. Mahesh.

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• Performance difference in for loop condition?

  - by CSharperWithJava

  Hello all, I have a simple question that I am posing mostly for my curiousity. What are the differences between these two lines of code? (in C++) for(int i = 0; i < N, N > 0; i++) for(int i = 0; i < N && N > 0; i++) The selection of the conditions is completely arbitrary, I'm just interested in the differences between , and &&. I'm not a beginner to coding by any means, but I've never bothered with the comma operator. Are there performance/behavior differences or is it purely aesthetic? One last note, I know there are bigger performance fish to fry than a conditional operator, but I'm just curious. Indulge me. Edit Thanks for your answers. It turns out the code that prompted this question had misused the comma operator in the way I've described. I wondered what the difference was and why it wasn't a && operator, but it was just written incorrectly. I didn't think anything was wrong with it because it worked just fine. Thanks for straightening me out.

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• How can I determine PerlLogHandler performance impact?

  - by Timmy

  I want to create a custom Apache2 log handler, and the template that is found on the apache site is: #file:MyApache2/LogPerUser.pm #--------------------------- package MyApache2::LogPerUser; use strict; use warnings; use Apache2::RequestRec (); use Apache2::Connection (); use Fcntl qw(:flock); use File::Spec::Functions qw(catfile); use Apache2::Const -compile => qw(OK DECLINED); sub handler { my $r = shift; my ($username) = $r->uri =~ m|^/~([^/]+)|; return Apache2::Const::DECLINED unless defined $username; my $entry = sprintf qq(%s [%s] "%s" %d %d\n), $r->connection->remote_ip, scalar(localtime), $r->uri, $r->status, $r->bytes_sent; my $log_path = catfile Apache2::ServerUtil::server_root, "logs", "$username.log"; open my $fh, ">>$log_path" or die "can't open $log_path: $!"; flock $fh, LOCK_EX; print $fh $entry; close $fh; return Apache2::Const::OK; } 1; What is the performance cost of the flocks? Is this logging process done in parallel, or in serial with the HTTP request? In parallel the performance would not matter as much, but I wouldn't want the user to wait another split second to add something like this.

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• MySQL Paritioning performance

  - by Imran Pathan

  Measured performance on key partitioned tables and normal tables separately. But we couldn't find any performance improvement with partitioning. Queries are pruned. Using MySQL 5.1.47 on RHEL 4. Table details: UserUsage - Will have entries for user mobile number and data usage for each date. Mobile number and Date as PRI KEY. UserProfile - Queries prev table and stores summary for each mobile number. Mobile number PRI KEY. CREATE TABLE `UserUsage` ( `Msisdn` decimal(20,0) NOT NULL, `Date` date NOT NULL, . . PRIMARY KEY USING BTREE (`Msisdn`,`Date`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 PARTITION BY KEY(Msisdn) PARTITIONS 50; CREATE TABLE `UserProfile` ( `Msisdn` decimal(20,0) NOT NULL, . . PRIMARY KEY (`Msisdn`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 PARTITION BY KEY(Msisdn) PARTITIONS 50; Second table is updated by query select and order by date in first table in a perl program, query is select * from UserUsage where Msisdn=number order by Date desc limit 7 [Process data in perl] update UserProfile values(....) where Msisdn=number explain partition for select, shows row being scanned in a particular partition only. Is something wrong with partition design or queries as partitioning is taking almost same or more time compared to normal tables?

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• Improve performance of searching JSON object with jQuery

  - by cale_b

  Please forgive me if this is answered on SO somewhere already. I've searched, and it seems as though this is a fairly specific case. Here's an example of the JSON (NOTE: this is very stripped down - this is dynamically loaded, and currently there are 126 records): var layout = { "2":[{"id":"40","attribute_id":"2","option_id":null,"design_attribute_id":"4","design_option_id":"131","width":"10","height":"10", "repeat":"0","top":"0","left":"0","bottom":"0","right":"0","use_right":"0","use_bottom":"0","apply_to_options":"0"}, {"id":"41","attribute_id":"2","option_id":"115","design_attribute_id":"4","design_option_id":"131","width":"2","height":"1", "repeat":"0","top":"0","left":"0","bottom":"4","right":"2","use_right":"0","use_bottom":"0","apply_to_options":"0"}, {"id":"44","attribute_id":"2","option_id":"118","design_attribute_id":"4","design_option_id":"131","width":"10","height":"10", "repeat":"0","top":"0","left":"0","bottom":"0","right":"0","use_right":"0","use_bottom":"0","apply_to_options":"0"}], "5":[{"id":"326","attribute_id":"5","option_id":null,"design_attribute_id":"4","design_option_id":"154","width":"5","height":"5", "repeat":"0","top":"0","left":"0","bottom":"0","right":"0","use_right":"0","use_bottom":"0","apply_to_options":"0"}] }; I need to match the right combination of values. Here's the function I currently use: function drawOption(attid, optid) { var attlayout = layout[attid]; $.each(attlayout, function(k, v) { // d_opt_id and d_opt_id are global scoped variable set elsewhere if (v.design_attribute_id == d_att_id && v.design_option_id == d_opt_id && v.attribute_id == attid && ((v.apply_to_options == 1 || (v.option_id === optid)))) { // Do stuff here } }); } The issue is that I might iterate through 10-15 layouts (unique attid's), and any given layout (attid) might have as many as 50 possibilities, which means that this loop is being run A LOT. Given the multiple criteria that have to be matched, would an AJAX call work better? (This JSON is dynamically created via PHP, so I could craft a PHP function that could possibly do this more efficently), or am I completely missing something about how to find items in a JSON object? As always, any suggestions for improving the code are welcome! EDIT: I apologize for not making this clear, but the purpose of this question is to find a way to improve the performance. The page has a lot of javascript, and this is a location where I know that performance is lower than it could be.

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• java + increasing performance and scalability

  - by varun

  Hi, below is the a code snippet, which returns the object of a class. now the object is basially comparing to some parameter in loop. my concern is what if there are thousands of objects in loop, in that case performance and scalability can be an issue. please suggest how to improve this code for performance part public Widget get(String name,int major,int minor,boolean exact) { Widget widgetToReturn = null; if(exact) { Widget w = new Widget(name, major, minor); // for loop using JDK 1.5 version for(Widget wid : set) { if((w.getName().equals(wid.getName())) && (wid.getVersion()).equals(w.getVersion())) { widgetToReturn = w; break; } } } else { Widget w = new Widget(name, major, minor); WidgetVersion widgetVersion = new WidgetVersion(major, minor); // for loop using JDK 1.5 version for(Widget wid : set) { WidgetVersion wv = wid.getVersion(); if((w.getName().equals(wid.getName())) && major == wv.getMajor() && WidgetVersion.isCompatibleAndNewer(wv, widgetVersion)) { widgetToReturn = wid; } else if((w.getName().equals(wid.getName())) && wv.equals(widgetVersion.getMajor(), widgetVersion.getMinor())) { widgetToReturn = w; } } } return widgetToReturn; }

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• Improving File Read Performance (single file, C++, Windows)

  - by david

  I have large (hundreds of MB or more) files that I need to read blocks from using C++ on Windows. Currently the relevant functions are: errorType LargeFile::read( void* data_out, __int64 start_position, __int64 size_bytes ) const { if( !m_open ) { // return error } else { seekPosition( start_position ); DWORD bytes_read; BOOL result = ReadFile( m_file, data_out, DWORD( size_bytes ), &bytes_read, NULL ); if( size_bytes != bytes_read || result != TRUE ) { // return error } } // return no error } void LargeFile::seekPosition( __int64 position ) const { LARGE_INTEGER target; target.QuadPart = LONGLONG( position ); SetFilePointerEx( m_file, target, NULL, FILE_BEGIN ); } The performance of the above does not seem to be very good. Reads are on 4K blocks of the file. Some reads are coherent, most are not. A couple questions: Is there a good way to profile the reads? What things might improve the performance? For example, would sector-aligning the data be useful? I'm relatively new to file i/o optimization, so suggestions or pointers to articles/tutorials would be helpful.

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• Socket Performance C++ Or C#

  - by modernzombie

  I have to write an application that is essentially a proxy server to handle all HTTP and HTTPS requests from our server (web browsing, etc). I know very little C++ and am very comfortable writing the application features in C#. I have experimented with the proxy from Mentalis (socket proxy) which seems to work fine for small webpages but if I go to large sites like tigerdirect.ca and browse through a couple of layers it is very slow and sometimes requests don't complete and I see broken images and javascript errors. This happens with all of our vendor sites and other content heavy sites. Mentalis uses HTTP 1.0 which I know is not as efficient but should a proxy be that slow? What is an acceptable amount of performance loss from using a proxy? Would HTTP 1.1 make a noticeable difference? Would a C++ proxy be much faster than one in C#? Is the Mentalis code just not efficient? Would I be able to use a premade C++ proxy and import the DLL to C# and still get good performance or would this project call for all C++? Sorry if these are obvious questions but I have not done network programming before.

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• Soap 1.2 Endpoint Performance

  - by mflair2000

  I have a Client WCF Host Service SOAP 1.2 Service setup and i'm having performance issues on the SOAP Java proxy. I have no control over how the Java service is setup, aside from the endpoint config. I have the Client running Asynchronously, and the host WCF service running in Async pattern, but i see the SOAP 1.2 proxy bottlenecking and handling the requests in a Synchronous way. Can someone take a look at the auto-generated SOAP 1.2 configuration below, from the SOAP 1.2 Service wsdl? Is there a way to configure this for Async way and improve performance? Could be configured for SOAP 1.1? <?xml version="1.0"?> <configuration> <system.web> <compilation debug="true"/> </system.web> <system.serviceModel> <bindings> <customBinding> <binding name="WebserviceListenerSoap12Binding" closeTimeout="00:30:00" openTimeout="00:30:00" receiveTimeout="00:30:00" sendTimeout="00:30:00"> <textMessageEncoding maxReadPoolSize="64" maxWritePoolSize="16" messageVersion="Soap12" writeEncoding="utf-8"> <readerQuotas maxDepth="32" maxStringContentLength="20000000" maxArrayLength="20000000" maxBytesPerRead="4096" maxNameTableCharCount="16384" /> </textMessageEncoding> <httpTransport manualAddressing="false" maxBufferPoolSize="20000000" maxReceivedMessageSize="20000000" allowCookies="false" authenticationScheme="Anonymous" bypassProxyOnLocal="false" decompressionEnabled="true" hostNameComparisonMode="StrongWildcard" keepAliveEnabled="true" maxBufferSize="20000000" proxyAuthenticationScheme="Anonymous" realm="" transferMode="Buffered" unsafeConnectionNtlmAuthentication="false" useDefaultWebProxy="true" /> </binding> </customBinding> </bindings> <client> <endpoint address="http://10.18.2.117:8080/java/webservice/WebserviceListener.WebserviceListenerHttpSoap12Endpoint/" binding="customBinding" bindingConfiguration="WebserviceListenerSoap12Binding" contract="ResolveServiceReference.WebserviceListenerPortType" name="WebserviceListenerHttpSoap12Endpoint" /> </client> </system.serviceModel> </configuration>

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• NHibernate Performance Optimization | Suggestions invited!!!

  - by user336749

  Hi, I’m facing an issue with NHibernate performance and can you please suggest me some optimizations? Below mentioned is a small summary of my application architecture I have a windows service which is listening to a messaging bus. On receiving a message the service creates an object out of which a property is the received xml snippet and saves the message to the DB (uses NH). There is a WPF UI with a readonly connection to the DB, and on refresh of the UI it displays the objects on the screen. While the UI does a refresh, it retrieves the xml and deserializes it , from which the object’s properties are derived and binded to the screen. For example assume an xml XXX is received by the service, it deserializes the xml , creates the book object and save it to the DB and a property/column is SCHEMA which contains the xml snippet. The UI while refreshed searches all book objects by ID and creates the book objects out of the xml which is being saved (yes, the xml is the constructor param). Now my issue is that the refresh takes more than 2 minutes to display say 50 book objects. I analyzed it using the NHibernate profiler, and found that the time spend within the DB is negligible, however time spent to create the entities is proportionally huge(10ms:1990 ms).I guess it’s due to the fairly huge size of xml snippet and it’s deserialization. My question is, how can I improve the performance. I dispose sessions after every refresh and is not lazy loading (please note that the time spend in DB is negligible). On every refresh it’s possible that all objects are updated by some downstream systems or maybe one of them are updated.Can I implement some sort of caching mechanism in this case? Thanks in advance for any suggestions. Regards, -Mike

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• Developers: How does BitLocker affect performance?

  - by Chris

  I'm an ASP.NET / C# developer. I use VS2010 all the time. I am thinking of enabling BitLocker on my laptop to protect the contents, but I am concerned about performance degradation. Developers who use IDEs like Visual Studio are working on lots and lots of files at once. More than the usual office worker, I would think. So I was curious if there are other developers out there who develop with BitLocker enabled. How has the performance been? Is it noticeable? If so, is it bad? My laptop is a 2.53GHz Core 2 Duo with 4GB RAM and an Intel X25-M G2 SSD. It's pretty snappy but I want it to stay that way. If I hear some bad stories about BitLocker, I'll keep doing what I am doing now, which is keeping stuff RAR'ed with a password when I am not actively working on it, and then SDeleting it when I am done (but it's such a pain).

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• Misaligned Pointer Performance

  - by Elite Mx

  Aren't misaligned pointers (in the BEST possible case) supposed to slow down performance and in the worst case crash your program (assuming the compiler was nice enough to compile your invalid c program). Well, the following code doesn't seem to have any performance differences between the aligned and misaligned versions. Why is that? /* brutality.c */ #ifdef BRUTALITY xs = (unsigned long *) ((unsigned char *) xs + 1); #endif ... /* main.c */ #include <stdio.h> #include <stdlib.h> #define size_t_max ((size_t)-1) #define max_count(var) (size_t_max / (sizeof var)) int main(int argc, char *argv[]) { unsigned long sum, *xs, *itr, *xs_end; size_t element_count = max_count(*xs) >> 4; xs = malloc(element_count * (sizeof *xs)); if(!xs) exit(1); xs_end = xs + element_count - 1; sum = 0; for(itr = xs; itr < xs_end; itr++) *itr = 0; #include "brutality.c" itr = xs; while(itr < xs_end) sum += *itr++; printf("%lu\n", sum); /* we could free the malloc-ed memory here */ /* but we are almost done */ exit(0); } Compiled and tested on two separate machines using gcc -pedantic -Wall -O0 -std=c99 main.c for i in {0..9}; do time ./a.out; done

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• ssh + tinyproxy: poor performance

  - by Paul

  I am currently in China and I would like to still visit some blocked websites (facebook, youtube). I have VPS in the USA and I have installed tinyproxy on it. I log in on my VPS with SSH port-forwarding and I have configured my browser appropriately. Everything works more or less: I can surf to those websites but everything is inusually slow and sometimes data transfer stops abruptly. This probably has to do with the fact that I see some errors in my shell on the VPS like : channel 6: open failed: connect failed: Also in the log-file of tinyproxy I see some bad things: ERROR Sep 06 14:52:14 [28150]: getpeer_information: getpeername() error: Transport endpoint is not connected ERROR Sep 06 14:52:15 [28153]: writebuff: write() error "Connection reset by peer" on file descriptor 7 ERROR Sep 06 14:52:15 [28168]: readbuff: recv() error "Connection reset by peer" on file descriptor 7 ERROR Sep 06 14:52:15 [28151]: readbuff: recv() error "Connection reset by peer" on file descriptor 7 ERROR Sep 06 14:52:15 [28143]: readbuff: recv() error "Connection reset by peer" on file descriptor 7 ERROR Sep 06 14:52:17 [28147]: writebuff: write() error "Connection reset by peer" on file descriptor 7 ERROR Sep 06 14:52:23 [28137]: writebuff: write() error "Connection reset by peer" on file descriptor 7 ERROR Sep 06 14:52:26 [28168]: getpeer_information: getpeername() error: Transport endpoint is not connected ERROR Sep 06 14:52:27 [28186]: read_request_line: Client (file descriptor: 7) closed socket before read. ERROR Sep 06 14:52:31 [28160]: getpeer_information: getpeername() error: Transport endpoint is not connected

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• Citrix Performance monitoring

  - by Dr I

  Hi people, I has a strange thing which appears on my Citrix Farm today. My users are equiped with a Thin client Axel Model 80F, and today, one of them sustained a problem on it. He opened a citrix's Publish Desktop session (Host by a farm of Windows 2003 R2 SP2 Servers), he loaded Lotus Notes and a mail who contained an PDF attached file. Once he has opened his PDF File, his session has freezed. We've just reboot the Thin Client, and log in again on the session (which hasn't been closed during the process). Once we have log in again, we try to read the pdf and once again afer half a page the session freeze again (I can see the mouse moving on the screen but can make anything). Then I close the session, reboot correctly the thin client, and "Tada" with the same manipulationsn averything is correct and we don't facing any freeze. Well Now my question is: Is that bug came from the thin client or the server about you? I've checked on my farm and I don't have any alert from the Citrix's Monitoring console logs. According to me it's due to the Thin Client BUT I ddon't have enought monitoring tools to be sure of that. So do you have some quite godd monitoring tools or method? My config: Windows 2003 R2 SP2 Citrix Xenapp 5.0

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• Websphere - Performance Monitoring Infrastructure servlet login GET

  - by virtual-lab

  I am trying to make an http call to the WebSphere PMI servlet. Websphere has security enabled and therefore I am asked to enter user credentials in order to display the xml. What actually doesn't work as I expect is that username and password in the url are not recognized and the BASIC authorization form is displayed. Obviously it doesn't work from a third party application point of view, I need to pass those variables as GET request. Any suggestion?

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• Poor home office network performance and cannot figure out where the issue is

  - by Jeff Willener

  This is the most bizarre issue. I have worked with small to mid size networks for quite a long time and can say I'm comfortable connecting hardware. Where you will start to lose me is with managed switches and firewalls. To start, let me describe my network (sigh, shouldn't but I MUST solve this). 1) Comcast Cable Internet 2) Motorola SURFboard eXtreme Cable Modem. a) Model: SB6120 b) DOCSIS 3.0 and 2.0 support c) IPv4 and IPv6 support 3-A) Cisco Small Business RV220W Wireless N Firewall a) Latest firmware b) Model: RV220W-A-K9-NA c) WAN Port to Modem (2) d) vlan 1: work e) vlan 2: everything else. 3-B) D-Link DIR-615 Draft 802.11 N Wireless Router a) Latest firmware b) WAN Port to Modem (2) 4) Servers connected directly to firewall a) If firewall 3-A, then vlan 1 b) CAT5e patch cables c) Dell PowerEdge 1400SC w/ 10/100 integrated NIC (Domain Controller, DNS, former DHCP) d) Dell PowerEdge 400SC w/ 10/100/1000 integrated NIC (VMWare Server) 4) Linksys EZXS88W unmanaged Workgroup 10/100 Switch a) If firewall 3-A, then vlan 2 b) 25' CAT5e patch cable to firewall (3-A or 3-B) c) Connects xBox 360, Blu-Ray player, PC at TV 5) Office equipment connected directly to firewall a) If firewall 3-A, then vlan 1 b) ~80' CAT6 or CAT5e patch cable to firewall (3-A or 3-B) c) Connects 1) Dell Latitude laptop 10/100/1000 2) Dell Inspiron laptop 10/100 3) Dell Workstation 10/100/1000 (Pristine host, VMWare Workstation 7.x with many bridged VM's) 4) Brother Laser Printer 10/100 5) Epson All-In-One Workforce 310 10/100 5-A) NetGear FS116 unmanaged 10/100 switch a) I've had this switch for a long time and never had issues. 5-B) NetGear GS108 unmanaged 10/100/1000 switch a) Bought new for this issue and returned. 5-C) Linksys SE2500 unmanaged 10/100/1000 switch a) Bought new for this issue and returned. 5-D) TP-Link TL-SG10008D unmanaged 10/100/1000 a) Bought new for this issue and still have. 6) VLan 1 Wireless Connections (on same subnet if 3-B) a) Any of those at 5c b) HP Laptop 7) VLan 2 Wireless Connection (on same subnet if 3-B) a) IPad, IPod b) Compaq Laptop c) Epson Wireless Printer Shew, without hosting a diagram I hope that paints a good picture. The Issue The breakdown here is at item 5. No matter what I do I cannot have a switch at 5 and have to run everything wireless regardless of router. Issues related to using a switch (point 5 above) SpeedTest is good. Poor throughput to other devices if can communicate at all. Usually cannot ping other devices even on the same switch although, when able, ping times are good. Eventual lose of connectivity and can "sometimes" be restored by unplugging everything for several days, not minutes or hours but we're talking a week if at all. Directly connect to computer gives good internet connection however throughput to other devices connected to firewall is at best horrible. Yet printing doesn't seem to be an issue as long as they are connected via wireless. I have to force the RV220W to 1000Mb on the respective port if using a Gig Switch Issues related to using wireless in place of a switch (point 5 above) Poor throughput to other devices if can communicate. SpeedTest is good. Bottom line Internet speeds are awesome. By the way, Comcast went WAY above and beyond to make sure it was not them. They rewired EVERYTHING which did solve internet drops. Computer to computer connections are garbage Cannot get switch at 5 to work, yet other at 4 has never had an issue. Direct connection, bypass switch, is good for DHCP and internet. DNS must be on server, not firewall. Cisco insists its my switches but as you can see I have used four and two different cables with the same result. My gut feeling is something is happening with routing. But I'm not smart enough to know that answer. I run a lot of VM's at 5-c-3, could that cause it? What's different compared to my previous house is I have introduced Gigabit hardware (firewall/switches/computers). Some of my computers might have IPv6 turned on if I haven't turned it off already. I'm truly at a loss and hope anyone has some crazy idea how to solve this. Bottom line, I need a switch in my office behind the firewall. I've changed everything. The real crux is I will find a working solution and, again, after days it will stop working. So this means I cannot isolate if its a computer since I have to use them. Oh and a solution is not throwing more money at this. I'm well into $1k already. Yah, lame.

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• Oracle performance problem

  - by jreid42

  We are using an Oracle 11G machine that is very powerful; has redundant storage etc. It's a beast from what I have been told. We just got this DB for a tool that when I first came on as a coop had like 20 people using, now its upwards of 150 people. I am the only one working on it :( We currently have a system in place that distributes PERL scripts across our entire data center essentially giving us a sort of "grid" computing power. The Perl scripts run a sort of simulation and report back the results to the database. They do selects / inserts. The load is not very high for each script but it could be happening across 20-50 systems at the same time. We then have multiple data centers and users all hitting the same database with this same approach. Our main problem with this is that our database is getting overloaded with connections and having to drop some. We sometimes have upwards of 500 connections. These are old perl scripts and they do not handle this well. Essentially they fail and the results are lost. I would rather avoid having to rewrite a lot of these as they are poorly written, and are a headache to even look at. The database itself is not overloaded, just the connection overhead is too high. We open a connection, make a quick query and then drop the connection. Very short connections but many of them. The database team has basically said we need to lower the number of connections or they are going to ignore us. Because this is distributed across our farm we cant implement persistent connections. I do this with our webserver; but its on a fixed system. The other ones are perl scripts that get opened and closed by the distribution tool and thus arent always running. What would be my best approach to resolving this issue? The scripts themselves can wait for a connection to be open. They do not need to act immediately. Some sort of queing system? I've been suggested to set up a few instances of a tool called "SQL Relay". Maybe one in each data center. How reliable is this tool? How good is this approach? Would it work for what we need? We could have one for each data center and relay requests through it to our main database, keeping a pipeline of open persistent connections? Does this make sense? Is there any other suggestions you can make? Any ideas? Any help would be greatly appreciated. Sadly I am just a coop student working for a very big company and somehow all of this has landed all on my shoulders (there is literally nobody to ask for help; its a hardware company, everybody is hardware engineers, and the database team is useless and in India) and I am quite lost as what the best approach would be? I am extremely overworked and this problem is interfering with on going progress and basically needs to be resolved as quickly as possible; preferably without rewriting the whole system, purchasing hardware (not gonna happen), or shooting myself in the foot. HELP LOL!

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• Nginx Fastcgi performance issues

  - by Barry

  I am running several fastcgi servers behind Nginx. I run 3 Nginx workers and 6 fastcgi servers as upstream backends. When I run load tests of 1 req per sec, I can clearly see that on avarage a reply is 0.1sec, but from time to time there are 3.1 sec responses. It is a suspiciously deterministic number and it happens even at very small loads from time to time. Both CPU and Memory are of no issue at all. Any idea where this delay may be comming from? Any suggestions how to debug this? Many thanks, Barry.

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• Ubuntu server has slow performance

  - by Rich

  I have a custom built Ubuntu 11.04 server with a 6 disk software RAID 10 primary drive. On it I'm primarily running a PostgreSQL and a few other utilities that stream data from the web. I often find after a few hours of uptime the server starts to lag with all kinds of processes. For example, it may take 10-15 seconds after log-in to get a shell prompt. It might take 5-10 seconds for top to come up. An ls might take a second or two. When I look at top there is almost no CPU usage. There's a fair amount of memory used by the PostgreSQL server but not enough to bleed into swap. I have no idea where to go from here, other than to suspect the RAID10 (I've only ever had software RAID 1's before). Edit: Output from top: top - 11:56:03 up 1:46, 3 users, load average: 0.89, 0.73, 0.72 Tasks: 119 total, 1 running, 118 sleeping, 0 stopped, 0 zombie Cpu(s): 0.2%us, 0.0%sy, 0.0%ni, 93.5%id, 6.2%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 16325596k total, 3478248k used, 12847348k free, 20880k buffers Swap: 19534176k total, 0k used, 19534176k free, 3041992k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1747 woodsp 20 0 109m 10m 4888 S 1 0.1 0:42.70 python 357 root 20 0 0 0 0 S 0 0.0 0:00.40 jbd2/sda3-8 1 root 20 0 24324 2284 1344 S 0 0.0 0:00.84 init 2 root 20 0 0 0 0 S 0 0.0 0:00.00 kthreadd 3 root 20 0 0 0 0 S 0 0.0 0:00.24 ksoftirqd/0 6 root RT 0 0 0 0 S 0 0.0 0:00.00 migration/0 7 root RT 0 0 0 0 S 0 0.0 0:00.01 watchdog/0 8 root RT 0 0 0 0 S 0 0.0 0:00.00 migration/1 10 root 20 0 0 0 0 S 0 0.0 0:00.02 ksoftirqd/1 12 root RT 0 0 0 0 S 0 0.0 0:00.01 watchdog/1 13 root RT 0 0 0 0 S 0 0.0 0:00.00 migration/2 14 root 20 0 0 0 0 S 0 0.0 0:00.00 kworker/2:0 15 root 20 0 0 0 0 S 0 0.0 0:00.00 ksoftirqd/2 16 root RT 0 0 0 0 S 0 0.0 0:00.01 watchdog/2 17 root RT 0 0 0 0 S 0 0.0 0:00.00 migration/3 18 root 20 0 0 0 0 S 0 0.0 0:00.00 kworker/3:0 19 root 20 0 0 0 0 S 0 0.0 0:00.02 ksoftirqd/3 20 root RT 0 0 0 0 S 0 0.0 0:00.01 watchdog/3 21 root 0 -20 0 0 0 S 0 0.0 0:00.00 cpuset 22 root 0 -20 0 0 0 S 0 0.0 0:00.00 khelper 23 root 20 0 0 0 0 S 0 0.0 0:00.00 kdevtmpfs 24 root 0 -20 0 0 0 S 0 0.0 0:00.00 netns 26 root 20 0 0 0 0 S 0 0.0 0:00.00 sync_supers df -h rpsharp@ncp-skookum:~$ df -h Filesystem Size Used Avail Use% Mounted on /dev/sda3 1.8T 549G 1.2T 32% / udev 7.8G 4.0K 7.8G 1% /dev tmpfs 3.2G 492K 3.2G 1% /run none 5.0M 0 5.0M 0% /run/lock none 7.8G 0 7.8G 0% /run/shm /dev/sda2 952M 128K 952M 1% /boot/efi /dev/md0 5.5T 562G 4.7T 11% /usr/local free -m psharp@ncp-skookum:~$ free -m total used free shared buffers cached Mem: 15942 3409 12533 0 20 2983 -/+ buffers/cache: 405 15537 Swap: 19076 0 19076 tail -50 /var/log/syslog Jul 3 06:31:32 ncp-skookum rsyslogd: [origin software="rsyslogd" swVersion="5.8.6" x-pid="1070" x-info="http://www.rsyslog.com"] rsyslogd was HUPed Jul 3 06:39:01 ncp-skookum CRON[14211]: (root) CMD ( [ -x /usr/lib/php5/maxlifetime ] && [ -d /var/lib/php5 ] && find /var/lib/php5/ -depth -mindepth 1 -maxdepth 1 -type f -cmin +$(/usr/lib/php5/maxlifetime) ! -execdir fuser -s {} 2>/dev/null \; -delete) Jul 3 06:40:01 ncp-skookum CRON[14223]: (smmsp) CMD (test -x /etc/init.d/sendmail && /usr/share/sendmail/sendmail cron-msp) Jul 3 07:00:01 ncp-skookum CRON[14328]: (woodsp) CMD (/home/woodsp/bin/mail_tweetupdate # email an update) Jul 3 07:00:01 ncp-skookum CRON[14327]: (smmsp) CMD (test -x /etc/init.d/sendmail && /usr/share/sendmail/sendmail cron-msp) Jul 3 07:00:28 ncp-skookum sendmail[14356]: q63E0SoZ014356: from=woodsp, size=2328, class=0, nrcpts=2, msgid=<[email protected]>, relay=woodsp@localhost Jul 3 07:00:29 ncp-skookum sm-mta[14357]: q63E0Si6014357: from=<[email protected]>, size=2569, class=0, nrcpts=2, msgid=<[email protected]>, proto=ESMTP, daemon=MTA-v4, relay=localhost [127.0.0.1] Jul 3 07:00:29 ncp-skookum sendmail[14356]: q63E0SoZ014356: to=Spencer Wood <[email protected]>,Martin Lacayo <[email protected]>, ctladdr=woodsp (1004/1005), delay=00:00:01, xdelay=00:00:01, mailer=relay, pri=62328, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (q63E0Si6014357 Message accepted for delivery) Jul 3 07:00:29 ncp-skookum sm-mta[14359]: STARTTLS=client, relay=mx3.stanford.edu., version=TLSv1/SSLv3, verify=FAIL, cipher=DHE-RSA-AES256-SHA, bits=256/256 Jul 3 07:00:29 ncp-skookum sm-mta[14359]: q63E0Si6014357: to=<[email protected]>,<[email protected]>, ctladdr=<[email protected]> (1004/1005), delay=00:00:01, xdelay=00:00:00, mailer=esmtp, pri=152569, relay=mx3.stanford.edu. [171.67.219.73], dsn=2.0.0, stat=Sent (Ok: queued as 8F3505802AC) Jul 3 07:09:08 ncp-skookum CRON[14396]: (root) CMD ( [ -x /usr/lib/php5/maxlifetime ] && [ -d /var/lib/php5 ] && find /var/lib/php5/ -depth -mindepth 1 -maxdepth 1 -type f -cmin +$(/usr/lib/php5/maxlifetime) ! -execdir fuser -s {} 2>/dev/null \; -delete) Jul 3 07:17:01 ncp-skookum CRON[14438]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly) Jul 3 07:20:01 ncp-skookum CRON[14453]: (smmsp) CMD (test -x /etc/init.d/sendmail && /usr/share/sendmail/sendmail cron-msp) Jul 3 07:39:01 ncp-skookum CRON[14551]: (root) CMD ( [ -x /usr/lib/php5/maxlifetime ] && [ -d /var/lib/php5 ] && find /var/lib/php5/ -depth -mindepth 1 -maxdepth 1 -type f -cmin +$(/usr/lib/php5/maxlifetime) ! -execdir fuser -s {} 2>/dev/null \; -delete) Jul 3 07:40:01 ncp-skookum CRON[14562]: (smmsp) CMD (test -x /etc/init.d/sendmail && /usr/share/sendmail/sendmail cron-msp) Jul 3 08:00:01 ncp-skookum CRON[14668]: (smmsp) CMD (test -x /etc/init.d/sendmail && /usr/share/sendmail/sendmail cron-msp) Jul 3 08:09:01 ncp-skookum CRON[14724]: (root) CMD ( [ -x /usr/lib/php5/maxlifetime ] && [ -d /var/lib/php5 ] && find /var/lib/php5/ -depth -mindepth 1 -maxdepth 1 -type f -cmin +$(/usr/lib/php5/maxlifetime) ! -execdir fuser -s {} 2>/dev/null \; -delete) Jul 3 08:17:01 ncp-skookum CRON[14766]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly) Jul 3 08:20:01 ncp-skookum CRON[14781]: (smmsp) CMD (test -x /etc/init.d/sendmail && /usr/share/sendmail/sendmail cron-msp) Jul 3 08:39:01 ncp-skookum CRON[14881]: (root) CMD ( [ -x /usr/lib/php5/maxlifetime ] && [ -d /var/lib/php5 ] && find /var/lib/php5/ -depth -mindepth 1 -maxdepth 1 -type f -cmin +$(/usr/lib/php5/maxlifetime) ! -execdir fuser -s {} 2>/dev/null \; -delete) Jul 3 08:40:01 ncp-skookum CRON[14892]: (smmsp) CMD (test -x /etc/init.d/sendmail && /usr/share/sendmail/sendmail cron-msp) Output of hdparm -t /dev/sd{a,b,c,d,e,f} This looks suspicious? /dev/sda: Timing buffered disk reads: 2 MB in 4.84 seconds = 423.39 kB/sec /dev/sdb: Timing buffered disk reads: 420 MB in 3.01 seconds = 139.74 MB/sec /dev/sdc: Timing buffered disk reads: 390 MB in 3.00 seconds = 129.87 MB/sec /dev/sdd: Timing buffered disk reads: 416 MB in 3.00 seconds = 138.51 MB/sec /dev/sde: Timing buffered disk reads: 422 MB in 3.00 seconds = 140.50 MB/sec /dev/sdf: Timing buffered disk reads: 416 MB in 3.01 seconds = 138.26 MB/sec

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• Poor NFS Performance: OpenFiler

  - by Safin09

  Good Day Everyone, I have an issue with OpenFiler, a Linux-based operating that converts a computer system into a SAN/NAS appliance. Here is the problem. In my environment we have two Netapp Storevault 500 appliances that I normally perform backups to a NFS share. There are two backup cronjobs that use ghettoVCB to backup two groups of VM's. One group is a pool of 3 VMs. This takes 13 mins to complete. A second job that backups a pool of 5 VMs to a 2nd Storevault appliance which takes 2 hours. We then installed Openfiler on a old server that has 2 core Xeon processors. There is a software RAID 5 process in place. When performing the same backups to a NFS Openfiler share, the first backup job, which takes 13 mins, takes around 4 hours. The second backup job, which takes 2 hours, takes almost 10 hours to complete. This is unacceptable!!!! Especially considering the strain placed on the host ESX Server. I assumed that because of the software RAID 5, the overhead on the CPU explained the long backup times. I then installed Openfiler on a 2nd server, an IBM x306 machine which has a P4 Intel processor. This time no software RAID or any RAID at all. A single 750GB hard drive that contained the OS and the rest of the disk uses to backup VMs to a NFS share. I performed the first backup job of the pool of 3 VMs. This time the backup job took 1 and 1/2 hours to complete instead of 13 mins!!!!!!!!!! Is Openfiler simply poor at being an NFS Server!!!!!!!!!!!!! Has anyone else had these issues with Openfiler?

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• apache performance improvements and maxclients

  - by updog

  I know this has been asked a few (thousand) times around the internet but I was hoping someone whose in the know might be able to comment on my particular setup. I have a web server hosting one site (php/codeigniter) with a wordpress blog in a sub directory. The server has 2GB RAM, 3GHz CPU and I have offloaded the static assets to CloudFlare which is has reduced bandwidth for the actual server by almost 75%. The problem I have is when an email campaign is sent out that links to the site or blog, it slows down. Below is my settings in apache2.conf. Average apache process size is 80M and there is 1.5GB available for apache. <IfModule mpm_prefork_module> StartServers 8 MinSpareServers 5 MaxSpareServers 20 MaxClients 20 MaxRequestsPerChild 2000 </IfModule> I have already setup and installed apc and built some caching into the site and used w3totalcache on the blog. The number of concurrent users is around 2-300 when there is a campaign, are there any further optimisations before

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• Wi-Fi performance in Windows 8 RP on a MacBook Air (mid 2011)

  - by Steven Lu

  I was able to install the Boot Camp Windows software using the executable that it provided, and there are no unrecognized or unknown devices in Device Manager. Wi-Fi works but it seems to be limited to an extremely slow 1.5Mbits. Network Center reports an 802.11n connection (at 65Mbps usually) but transfers never reach above about 200kB/s. Being limited to 1/20th of the connection speed of my internet service is quite frustrating. Does anybody experience the same issue? I have been trying to identify the Broadcom Wi-Fi chipset and a driver that I could try to upgrade to but I have made very little progress on Google on this front.

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• Performance issue when configuring non HA VM in cluster

  - by laiys

  Hi, I saw this article http://technet.microsoft.com/en-us/library/cc764243.aspx Quote taken from the link “ Important It is recommended that you not deploy virtual machines that are not highly available on your host clusters. Although you can do this by using Hyper-V (VMM does not allow it), the non-highly available virtual machines will consume resources that otherwise would be available to the HAVMs What kind of resources (CPU,memory, NIC, etc) that non HA VM will consume? Just curious as not all VM (in production) not to be in Failover Cluster and Live Migration. If i put the VM into CSV but did not make it as HA, what impact does it make since i allocate same vCPU, vNic and VMemory into the VM. (not to mention that i lost failover feature). Curious to understand more about this. Please advise. Thanks

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