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  • How do you gracefully upgrade mission critical systems to wildly disparate systems?

    - by Ernie
    In the span of the 12+ years of my career, I have yet to overcome this hurdle and I suspect the answer simply isn't easy or even possible, so I ask everyone here for their experience. Say that you're running into egregious problems that can only be fixed by moving from one platform to another - either from making a mistake in choosing the platform that was chosen years ago, or simply growing beyond what the system was originally designed for. You know for certain that the cruft that has built up over time will invariably mean that it will be nearly impossible to test for all the things that will certainly lead to tech support hell - which we all know leads to the loss of customers. Not that customers aren't already complaining about the egregious problems that already exist! The best possible way that I've discovered so far is to maybe devise a plan for the changeover, test it on a few clients, test it on a dozen clients, test it on a hundred clients, then finally finish the changeover for everyone and pray that you've worked out all the bugs with those first hundred and twenty, and that the animal by-products will not hit the ventilation system in the most spectacular fashion possible. However, that doesn't mean that it won't anyway. So say that you're moving from Exchange to Exim (or even just Sendmail to Exim). How do you handle it?

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  • What is the cleanest way to upgrade Fedora and also my individual installs while keeping /home?

    - by Don
    I am a professional programmer, using Fedora 10 (and a host of other packages individually installed). I use my system to telecommute. Every year or so, I go through the ritual dance, usually with a second computer and a KVM switch as I don't have office space for two monitors, to build the next version of Fedora and install all my favorite apps. Is there a better way? At least a nice way to keep track of what I need to 'add on' so that I don't have to manually install my app collection? Also, I keep /home on a separate raid-ed drive set so I can also fall prey to 'old-config-file-itis'.

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  • Cannot SSH anymore, what went wrong?

    - by lbwtz2
    I use to ssh to a remote server (no rsa-key, just password). Now the server do not accept the connection any more and throw me this error: ssh_exchange_identification: Connection closed by remote host While I can google a little to find a fix I can't figure out what went wrong since I haven't touched anything on the machine since last login. Can you help me find the cause? EDIT: Inspecting the logs I've found these: /var/auth.log /var/log/auth.log:Dec 26 16:40:32 vps sshd[15567]: error: fork: Cannot allocate memory /var/log/auth.log:Dec 26 16:41:05 vps sshd[15567]: error: fork: Cannot allocate memory /var/log/auth.log:Dec 26 16:43:47 vps sshd[15567]: error: fork: Cannot allocate memory /var/log/auth.log:Dec 27 03:20:06 vps sshd[15567]: error: fork: Cannot allocate memory /var/log/auth.log:Dec 27 16:15:02 vps sshd[15567]: error: fork: Cannot allocate memory And in the same span-time I've also found a lot of these: /var/log/auth.log:Dec 26 13:00:01 vps CRON[1716]: PAM unable to dlopen(/lib/security/pam_unix.so): libcrypt.so.1: cannot map zero-fill pages: Cannot allocate memory /var/log/auth.log:Dec 26 13:00:01 vps CRON[1716]: PAM adding faulty module: /lib/security/pam_unix.so What are these?

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  • when to upgrade server to include more cores, versus more processors, versus additional server?

    - by gkdsp
    The server hosting market is separated into single, double, qual, etc., processors, where each processor has several cores, or CPUs. My company will offer a Linux-based web application that relies on an Apache web server and a middle tier for business logic. The middle tier is used to crunch math, and return result to a client. Many clients may access the application simultaneously. The company will start with one processor having 4 cores. I'm trying to understand how the app uses the cores and then how to scale the application as business grows, in terms of servers/processors/cores. For example, I'd assume initially one core would be used for Apache, and the other 3 used to process client's requests for math crunching... Question 1: does that mean, with the 3 cores available, I can handle 3 separate client requests simultaneously (e.g. 1 for each of 3 cores)? I mean, except for the shared RAM, is this effectively like having 3 individual machines (from pt of view or processing client requests simulaneously)? Or, only one client's request may be processed at any one time, but that client's request is divided up into up to 3 cores depending on the type of process running that does the math crunching and whether or not it can take advantage of multi threading (so the # of cores impacts how fast any one client request completes)? I'm confused about what the cores mean to the application here. Question 2: As the business grows and more client requests need to be processed, should the server be upgraded to (A) a new machine with more cores, (B) a new machine with two processors, 4 cores each, or (C) keep the original server and add another server with a single processor? Which route provides the most efficient way to scale the application, in terms of processing more client requests per time interval? Is the choice, for example, limited by RAM (when you need more RAM than box can handle it's time to add another server), or something else? Question 3: Is the total number of client requests processed simultaneously equal to the number of cores times the number of servers (minus the one core for Apache)?

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  • What's the easiest way to upgrade a single laptop hard drive?

    - by rutherford
    My HD is coming near the end of it's life and I wondered if producing an image of the original was all that was required? What's the best software to use for this and how can I accomplish it - can I use my other laptop for the image file or do I need to buy an external HD to accomplish the clone? Does having several partitions of both FAT32 and NTFS with partition magic installed affect things at all? Is it just a matter of making the image, swapping in the new HD and copying the image to that?

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  • Why can't I access the WebUI of my DNS-323 NAS after a firmware upgrade?

    - by anonymous2
    Hi Everyone, I just bought a D-Link DNS-323 NAS Enclosure, and have run into a problem. I read that the firmware that had shipped with (1.07) did not support 2TB drives, so I downloaded firmware 1.08. Turned on the device for thwe first time and went straight to the WebUI (everything looked/worked fine) Proceeded with the firmware update, completed successfully. Rebooted and I cannot access the WebUI. I can see the NAS connected via my router interface I can also ping the ip adress assigned, but I cannot access the WebUI or find it via D-Link easy search software. I have tried the factory reset button, but that does not seem to be doing anything, the square blue light just keeps flashing from the moment the unit is powered on, whether I press the reset button or not, and the symptoms remain the same... PS. I did/do not have any drives installed yet. Please help?

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  • Can't create system image. 0x80780119 error after upgrade from 8 to 8.1

    - by cichy202
    I have upgraded my Windows 8 PC to 8.1 yesterday and it seemed like everything is working fine until I tried to create System Image. I got an error 0x80780119 saying that there is to little space on one of the partitions. I started looking into this problem and indeed one of the partitions does not meet the requirements. There are following partitions on my drive: DISKPART> list partition Partition ### Type Size Offset ------------- ---------------- ------- ------- Partition 1 Recovery 300 MB 1024 KB Partition 2 System 100 MB 301 MB Partition 3 Reserved 128 MB 401 MB Partition 4 Primary 74 GB 529 MB Partition 5 Primary 390 GB 75 GB Partition 1 has only 13MB free space. Partition 2 has 70MB free space, partition 3 is MSFTRES, partition 4 is my C drive with around 35GB free and partition 5 is not included in system image. Partitions were create like this during installation of Windows 8 - clean install from scratch. I am using UEFI so the drive is GPT formatted. So I thought, OK I can resize my C drive a little, move the partitions and expand the 1st one. I tried using GParted but it is not able to move the MSFTRES partition. It does not recognize the file system on it. So the question is: Is it possible to "clean up" the 1st partition in anyway? If not, is there anything special about MSFTRES partition? Or can I just remove it and create it a little further and just flag it as msftres with GParted?

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  • Asus ux31e zenbook SSD non-standard / cant upgrade hdd?

    - by FstaRocka
    I bought a ux31e asus zenbook, and the drive crashed last week. I just cancelled an mSata ssd order because I fear asus has used a non standard ssd!!! what a bunch of crooks, ive lost all my respect for this company! Can anyone confirm what and why? My SSD model is xm11 128gb - it looks like a ram chip and only has two tongues with 12 and 6 pins respectively. The drive I was about to order mSata had 8 where mine had 6 - i never bothered counting the rest. This article seems to confirm! UX31 UX21 Zenbook Article "It looks like SSD uses a non-standard format"

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  • How do I upgrade to PHP 5.4 in CentOS 6.3 with yum?

    - by Vicary
    I found some blog posts about this, but it's rather lack of descriptions on possible side effects. I could really use some detailed on these steps: How to add a repo that provides PHP 5.4 into yum Can this seamlessly replaces the current PHP version in CentOS? How can I switch back to the official repo when it supports PHP 5.4? (current 5.3.3 in my system) Will there be any potential to break PHP modules I currently using?

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  • How do I upgrade mongodb 1.8 to 2.2 on ubuntu?

    - by Alex Waters
    Following this guide: http://docs.mongodb.org/manual/tutorial/install-mongodb-on-ubuntu/ I ended up with mongodb 18 on my Ubuntu 10.04. I've just read the 2.2 mongodb release notes on upgrading and it says to just replace the binary. Would that be /usr/lib/mongodb/mongod ? It looks like the 2.2 tar has several files I might need to copy over: mongo, mongod, mongoexport, mongodump, mongofiles, mongoimport, mongorestore, mongos, xulwrapper Can I just copy and paste all of those over to replace the old versions of those files?

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  • 10 Windows Tweaking Myths Debunked

    - by Chris Hoffman
    Windows is big, complicated, and misunderstood. You’ll still stumble across bad advice from time to time when browsing the web. These Windows tweaking, performance, and system maintenance tips are mostly just useless, but some are actively harmful. Luckily, most of these myths have been stomped out on mainstream sites and forums. However, if you start searching the web, you’ll still find websites that recommend you do these things. Erase Cache Files Regularly to Speed Things Up You can free up disk space by running an application like CCleaner, another temporary-file-cleaning utility, or even the Windows Disk Cleanup tool. In some cases, you may even see an old computer speed up when you erase a large amount of useless files. However, running CCleaner or similar utilities every day to erase your browser’s cache won’t actually speed things up. It will slow down your web browsing as your web browser is forced to redownload the files all over again, and reconstruct the cache you regularly delete. If you’ve installed CCleaner or a similar program and run it every day with the default settings, you’re actually slowing down your web browsing. Consider at least preventing the program from wiping out your web browser cache. Enable ReadyBoost to Speed Up Modern PCs Windows still prompts you to enable ReadyBoost when you insert a USB stick or memory card. On modern computers, this is completely pointless — ReadyBoost won’t actually speed up your computer if you have at least 1 GB of RAM. If you have a very old computer with a tiny amount of RAM — think 512 MB — ReadyBoost may help a bit. Otherwise, don’t bother. Open the Disk Defragmenter and Manually Defragment On Windows 98, users had to manually open the defragmentation tool and run it, ensuring no other applications were using the hard drive while it did its work. Modern versions of Windows are capable of defragmenting your file system while other programs are using it, and they automatically defragment your disks for you. If you’re still opening the Disk Defragmenter every week and clicking the Defragment button, you don’t need to do this — Windows is doing it for you unless you’ve told it not to run on a schedule. Modern computers with solid-state drives don’t have to be defragmented at all. Disable Your Pagefile to Increase Performance When Windows runs out of empty space in RAM, it swaps out data from memory to a pagefile on your hard disk. If a computer doesn’t have much memory and it’s running slow, it’s probably moving data to the pagefile or reading data from it. Some Windows geeks seem to think that the pagefile is bad for system performance and disable it completely. The argument seems to be that Windows can’t be trusted to manage a pagefile and won’t use it intelligently, so the pagefile needs to be removed. As long as you have enough RAM, it’s true that you can get by without a pagefile. However, if you do have enough RAM, Windows will only use the pagefile rarely anyway. Tests have found that disabling the pagefile offers no performance benefit. Enable CPU Cores in MSConfig Some websites claim that Windows may not be using all of your CPU cores or that you can speed up your boot time by increasing the amount of cores used during boot. They direct you to the MSConfig application, where you can indeed select an option that appears to increase the amount of cores used. In reality, Windows always uses the maximum amount of processor cores your CPU has. (Technically, only one core is used at the beginning of the boot process, but the additional cores are quickly activated.) Leave this option unchecked. It’s just a debugging option that allows you to set a maximum number of cores, so it would be useful if you wanted to force Windows to only use a single core on a multi-core system — but all it can do is restrict the amount of cores used. Clean Your Prefetch To Increase Startup Speed Windows watches the programs you run and creates .pf files in its Prefetch folder for them. The Prefetch feature works as a sort of cache — when you open an application, Windows checks the Prefetch folder, looks at the application’s .pf file (if it exists), and uses that as a guide to start preloading data that the application will use. This helps your applications start faster. Some Windows geeks have misunderstood this feature. They believe that Windows loads these files at boot, so your boot time will slow down due to Windows preloading the data specified in the .pf files. They also argue you’ll build up useless files as you uninstall programs and .pf files will be left over. In reality, Windows only loads the data in these .pf files when you launch the associated application and only stores .pf files for the 128 most recently launched programs. If you were to regularly clean out the Prefetch folder, not only would programs take longer to open because they won’t be preloaded, Windows will have to waste time recreating all the .pf files. You could also modify the PrefetchParameters setting to disable Prefetch, but there’s no reason to do that. Let Windows manage Prefetch on its own. Disable QoS To Increase Network Bandwidth Quality of Service (QoS) is a feature that allows your computer to prioritize its traffic. For example, a time-critical application like Skype could choose to use QoS and prioritize its traffic over a file-downloading program so your voice conversation would work smoothly, even while you were downloading files. Some people incorrectly believe that QoS always reserves a certain amount of bandwidth and this bandwidth is unused until you disable it. This is untrue. In reality, 100% of bandwidth is normally available to all applications unless a program chooses to use QoS. Even if a program does choose to use QoS, the reserved space will be available to other programs unless the program is actively using it. No bandwidth is ever set aside and left empty. Set DisablePagingExecutive to Make Windows Faster The DisablePagingExecutive registry setting is set to 0 by default, which allows drivers and system code to be paged to the disk. When set to 1, drivers and system code will be forced to stay resident in memory. Once again, some people believe that Windows isn’t smart enough to manage the pagefile on its own and believe that changing this option will force Windows to keep important files in memory rather than stupidly paging them out. If you have more than enough memory, changing this won’t really do anything. If you have little memory, changing this setting may force Windows to push programs you’re using to the page file rather than push unused system files there — this would slow things down. This is an option that may be helpful for debugging in some situations, not a setting to change for more performance. Process Idle Tasks to Free Memory Windows does things, such as creating scheduled system restore points, when you step away from your computer. It waits until your computer is “idle” so it won’t slow your computer and waste your time while you’re using it. Running the “Rundll32.exe advapi32.dll,ProcessIdleTasks” command forces Windows to perform all of these tasks while you’re using the computer. This is completely pointless and won’t help free memory or anything like that — all you’re doing is forcing Windows to slow your computer down while you’re using it. This command only exists so benchmarking programs can force idle tasks to run before performing benchmarks, ensuring idle tasks don’t start running and interfere with the benchmark. Delay or Disable Windows Services There’s no real reason to disable Windows services anymore. There was a time when Windows was particularly heavy and computers had little memory — think Windows Vista and those “Vista Capable” PCs Microsoft was sued over. Modern versions of Windows like Windows 7 and 8 are lighter than Windows Vista and computers have more than enough memory, so you won’t see any improvements from disabling system services included with Windows. Some people argue for not disabling services, however — they recommend setting services from “Automatic” to “Automatic (Delayed Start)”. By default, the Delayed Start option just starts services two minutes after the last “Automatic” service starts. Setting services to Delayed Start won’t really speed up your boot time, as the services will still need to start — in fact, it may lengthen the time it takes to get a usable desktop as services will still be loading two minutes after booting. Most services can load in parallel, and loading the services as early as possible will result in a better experience. The “Delayed Start” feature is primarily useful for system administrators who need to ensure a specific service starts later than another service. If you ever find a guide that recommends you set a little-known registry setting to improve performance, take a closer look — the change is probably useless. Want to actually speed up your PC? Try disabling useless startup programs that run on boot, increasing your boot time and consuming memory in the background. This is a much better tip than doing any of the above, especially considering most Windows PCs come packed to the brim with bloatware.     

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  • Multiple vulnerabilities in Firefox

    - by Ritwik Ghoshal
    CVE DescriptionCVSSv2 Base ScoreComponentProduct and Resolution CVE-2012-3982 Denial of service (DoS) vulnerability 10.0 Firefox Solaris 10 SPARC: 145080-13 X86: 145081-12 CVE-2012-3983 Denial of service (DoS) vulnerability 10.0 CVE-2012-3986 Permissions, Privileges, and Access Controls vulnerability 6.4 CVE-2012-3988 Resource Management Errors vulnerability 9.3 CVE-2012-3990 Resource Management Errors vulnerability 10.0 CVE-2012-3991 Permissions, Privileges, and Access Controls vulnerability 9.3 CVE-2012-3992 Permissions, Privileges, and Access Controls vulnerability 5.8 CVE-2012-3993 Design Error vulnerability 9.3 CVE-2012-3994 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability 4.3 CVE-2012-3995 Improper Restriction of Operations within the Bounds of a Memory Buffer vulnerability 10.0 CVE-2012-4179 Resource Management Errors vulnerability 10.0 CVE-2012-4180 Improper Restriction of Operations within the Bounds of a Memory Buffer vulnerability 10.0 CVE-2012-4181 Resource Management Errors vulnerability 10.0 CVE-2012-4182 Resource Management Errors vulnerability 10.0 CVE-2012-4183 Resource Management Errors vulnerability 10.0 CVE-2012-4184 Permissions, Privileges, and Access Controls vulnerability 9.3 CVE-2012-4185 Improper Restriction of Operations within the Bounds of a Memory Buffer vulnerability 10.0 CVE-2012-4186 Improper Restriction of Operations within the Bounds of a Memory Buffer vulnerability 10.0 CVE-2012-4187 Improper Restriction of Operations within the Bounds of a Memory Buffer vulnerability 10.0 CVE-2012-4188 Improper Restriction of Operations within the Bounds of a Memory Buffer vulnerability 10.0 CVE-2012-4192 Permissions, Privileges, and Access Controls vulnerability 4.3 CVE-2012-4193 Design Error vulnerability 9.3 CVE-2012-4194 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability 4.3 CVE-2012-4195 Permissions, Privileges, and Access Controls vulnerability 5.1 CVE-2012-4196 Permissions, Privileges, and Access Controls vulnerability 5.0 This notification describes vulnerabilities fixed in third-party components that are included in Oracle's product distributions.Information about vulnerabilities affecting Oracle products can be found on Oracle Critical Patch Updates and Security Alerts page. Note: Solaris 10 patches SPARC: 145080-13 X86: 145081-12 contain the fix for all CVEs between Firefox version 10.0.7 and 10.0.12.

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  • Ubuntu 13.10, kernel 3.11 blank screen issue with hybrid graphics

    - by Lagerbaer
    On my HP Envy, which has both an Intel on-chip graphics card and an Nvidia Geforce: *-display UNCLAIMED description: 3D controller product: GK208M [GeForce GT 740M] vendor: NVIDIA Corporation physical id: 0 bus info: pci@0000:01:00.0 version: a1 width: 64 bits clock: 33MHz capabilities: cap_list configuration: latency=0 resources: memory:d2000000-d2ffffff memory:a0000000-afffffff memory:b0000000-b1ffffff ioport:5000(size=128) memory:b2000000-b207ffff *-display description: VGA compatible controller product: 4th Gen Core Processor Integrated Graphics Controller vendor: Intel Corporation physical id: 2 bus info: pci@0000:00:02.0 version: 06 width: 64 bits clock: 33MHz capabilities: vga_controller bus_master cap_list rom configuration: driver=i915 latency=0 resources: irq:46 memory:d3000000-d33fffff memory:c0000000-cfffffff ioport:6000(size=64) I have trouble with all newer kernels. I basically had to install 12.04 LTS and use their 3.5 kernel family to get the system to boot. The 3.8 from 12.10 or the newest 3.11 from Ubuntu 13.10 leave me with a black screen upon boot. On one occasion I did hear the "log in" sound, but the screen did not display anything. I have purged all nvidia drivers so I guess it should just use the intel drivers, but apparently this is all messed up with newer kernel versions. This is different from the other "nvidia boots into blank screen" bug in that I don't rely solely on an nvidia card. Surely the intel on-chip card should be supported and leave me with something different from a blank screen? Again, it only works with kernel versions 3.5.0-41-generic, not with the 3.11.0-12 one that ships with Ubuntu 13.10. When I go into the grub menu and change the boot options from 'quiet splash' to 'nomodeset' I am able to boot the system, but then I don't get any graphics and trying 'sudo service lightdm start' doesn't succeed (I get 100% CPU for apport, but this doesn't do anything either, so I kill it). Help, I'm all out of ideas. EDIT: Let me add that I'm using the EFI boot system and have a dual-boot installation with Windows 8.

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  • cannot boot ubuntu 13.10 with my usb, Can i change the kernal on my laptop to run it?

    - by Carlos Dunick
    Currently i am running 12.04 and looking for an upgrade to 13.10 I first tried a bootable 64bit usb and failed. With the message saying "Kernal requires an x86-64 CPU but only detected an I686 CPU Unable to boot please use a kernal appropriate for your CPU" then tried 32bit and same message came up. Is this due to my laptop simply being to slow? or can/should i change the kernal somehow? Acer Aspire 5710z Intel Pentium dual core processor, 1.73Ghz, 533 MHz FSB, 1 MB L2 cache. 2GB DDR2 lspci 00:00.0 Host bridge: Intel Corporation Mobile 945GM/PM/GMS, 943/940GML and 945GT Express Memory Controller Hub (rev 03) 00:02.0 VGA compatible controller: Intel Corporation Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller (rev 03) 00:02.1 Display controller: Intel Corporation Mobile 945GM/GMS/GME, 943/940GML Express Integrated Graphics Controller (rev 03) 00:1b.0 Audio device: Intel Corporation NM10/ICH7 Family High Definition Audio Controller (rev 02) 00:1c.0 PCI bridge: Intel Corporation NM10/ICH7 Family PCI Express Port 1 (rev 02) 00:1c.2 PCI bridge: Intel Corporation NM10/ICH7 Family PCI Express Port 3 (rev 02) 00:1c.3 PCI bridge: Intel Corporation NM10/ICH7 Family PCI Express Port 4 (rev 02) 00:1d.0 USB controller: Intel Corporation NM10/ICH7 Family USB UHCI Controller #1 (rev 02) 00:1d.1 USB controller: Intel Corporation NM10/ICH7 Family USB UHCI Controller #2 (rev 02) 00:1d.2 USB controller: Intel Corporation NM10/ICH7 Family USB UHCI Controller #3 (rev 02) 00:1d.3 USB controller: Intel Corporation NM10/ICH7 Family USB UHCI Controller #4 (rev 02) 00:1d.7 USB controller: Intel Corporation NM10/ICH7 Family USB2 EHCI Controller (rev 02) 00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev e2) 00:1f.0 ISA bridge: Intel Corporation 82801GBM (ICH7-M) LPC Interface Bridge (rev 02) 00:1f.1 IDE interface: Intel Corporation 82801G (ICH7 Family) IDE Controller (rev 02) 00:1f.2 SATA controller: Intel Corporation 82801GBM/GHM (ICH7-M Family) SATA Controller [AHCI mode] (rev 02) 00:1f.3 SMBus: Intel Corporation NM10/ICH7 Family SMBus Controller (rev 02) 04:00.0 Ethernet controller: Broadcom Corporation NetLink BCM5787M Gigabit Ethernet PCI Express (rev 02) 05:00.0 Network controller: Broadcom Corporation BCM4311 802.11b/g WLAN (rev 01) 06:00.0 FLASH memory: ENE Technology Inc ENE PCI Memory Stick Card Reader Controller 06:00.1 SD Host controller: ENE Technology Inc ENE PCI SmartMedia / xD Card Reader Controller 06:00.2 FLASH memory: ENE Technology Inc Memory Stick Card Reader Controller 06:00.3 FLASH memory: ENE Technology Inc ENE PCI Secure Digital / MMC Card Reader Controller

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  • String Sharing/Reference issue with objects in Delphi

    - by jenakai123
    My application builds many objects in memory based on filenames (among other string based information). I was hoping to optimise memory usage by storing the path and filename separately, and then sharing the path between objects in the same path. I wasn't trying to look at using a string pool or anything, basically my objects are sorted so if I have 10 objects with the same path I want objects 2-10 to have their path "pointed" at object 1's path (eg object[2].Path=object[1].Path); I have a problem though, I don't believe that my objects are in fact sharing a reference to the same string after I think I am telling them to (by the object[2].Path=object[1].Path assignment). When I do an experiment with a string list and set all the values to point to the first value in the list I can see the "memory conservation" in action, but when I use objects I see absolutely no change at all, admittedly I am only using task manager (private working set) to watch for memory use changes. Here's a contrived example, I hope this makes sense. I have an object: TfileObject=class(Tobject) FpathPart: string; FfilePart: string; end; Now I create 1,000,000 instances of the object, using a new string for each one: var x: integer; MyFilePath: string; fo: TfileObject; begin for x := 1 to 1000000 do begin // create a new string for every iteration of the loop MyFilePath:=ExtractFilePath(Application.ExeName); fo:=TfileObject.Create; fo.FpathPart:=MyFilePath; FobjectList.Add(fo); end; end; Run this up and task manager says I am using 68MB of memory or something. (Note that if I allocated MyFilePath outside of the loop then I do save memory because of 1 instance of the string, but this is a contrived example and not actually how it would happen in the app). Now I want to "optimise" my memory usage by making all objects share the same instance of the path string, since it's the same value: var x: integer; begin for x:=1 to FobjectList.Count-1 do begin TfileObject(FobjectList[x]).FpathPart:=TfileObject(FobjectList[0]).FpathPart; end; end; Task Manager shows absouletly no change. However if I do something similar with a TstringList: var x: integer; begin for x := 1 to 1000000 do begin FstringList.Add(ExtractFilePath(Application.ExeName)); end; end; Task Manager says 60MB memory use. Now optimise with: var x: integer; begin for x := 1 to FstringList.Count - 1 do FstringList[x]:=FstringList[0]; end; Task Manager shows the drop in memory usage that I would expect, now 10MB. So I seem to be able to share strings in a string list, but not in objects. I am obviously missing something conceptually, in code or both! I hope this makes sense, I can really see the ability to conserve memory using this technique as I have a lot of objects all with lots of string information, that data is sorted in many different ways and I would like to be able to iterate over this data once it is loaded into memory and free some of that memory back up again by sharing strings in this way. Thanks in advance for any assistance you can offer.

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  • .NET Code Evolution

    - by Alois Kraus
    Originally posted on: http://geekswithblogs.net/akraus1/archive/2013/07/24/153504.aspxAt my day job I do look at a lot of code written by other people. Most of the code is quite good and some is even a masterpiece. And there is also code which makes you think WTF… oh it was written by me. Hm not so bad after all. There are many excuses reasons for bad code. Most often it is time pressure followed by not enough ambition (who cares) or insufficient training. Normally I do care about code quality quite a lot which makes me a (perceived) slow worker who does write many tests and refines the code quite a lot because of the design deficiencies. Most of the deficiencies I do find by putting my design under stress while checking for invariants. It does also help a lot to step into the code with a debugger (sometimes also Windbg). I do this much more often when my tests are red. That way I do get a much better understanding what my code really does and not what I think it should be doing. This time I do want to show you how code can evolve over the years with different .NET Framework versions. Once there was  time where .NET 1.1 was new and many C++ programmers did switch over to get rid of not initialized pointers and memory leaks. There were also nice new data structures available such as the Hashtable which is fast lookup table with O(1) time complexity. All was good and much code was written since then. At 2005 a new version of the .NET Framework did arrive which did bring many new things like generics and new data structures. The “old” fashioned way of Hashtable were coming to an end and everyone used the new Dictionary<xx,xx> type instead which was type safe and faster because the object to type conversion (aka boxing) was no longer necessary. I think 95% of all Hashtables and dictionaries use string as key. Often it is convenient to ignore casing to make it easy to look up values which the user did enter. An often followed route is to convert the string to upper case before putting it into the Hashtable. Hashtable Table = new Hashtable(); void Add(string key, string value) { Table.Add(key.ToUpper(), value); } This is valid and working code but it has problems. First we can pass to the Hashtable a custom IEqualityComparer to do the string matching case insensitive. Second we can switch over to the now also old Dictionary type to become a little faster and we can keep the the original keys (not upper cased) in the dictionary. Dictionary<string, string> DictTable = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase); void AddDict(string key, string value) { DictTable.Add(key, value); } Many people do not user the other ctors of Dictionary because they do shy away from the overhead of writing their own comparer. They do not know that .NET has for strings already predefined comparers at hand which you can directly use. Today in the many core area we do use threads all over the place. Sometimes things break in subtle ways but most of the time it is sufficient to place a lock around the offender. Threading has become so mainstream that it may sound weird that in the year 2000 some guy got a huge incentive for the idea to reduce the time to process calibration data from 12 hours to 6 hours by using two threads on a dual core machine. Threading does make it easy to become faster at the expense of correctness. Correct and scalable multithreading can be arbitrarily hard to achieve depending on the problem you are trying to solve. Lets suppose we want to process millions of items with two threads and count the processed items processed by all threads. A typical beginners code might look like this: int Counter; void IJustLearnedToUseThreads() { var t1 = new Thread(ThreadWorkMethod); t1.Start(); var t2 = new Thread(ThreadWorkMethod); t2.Start(); t1.Join(); t2.Join(); if (Counter != 2 * Increments) throw new Exception("Hmm " + Counter + " != " + 2 * Increments); } const int Increments = 10 * 1000 * 1000; void ThreadWorkMethod() { for (int i = 0; i < Increments; i++) { Counter++; } } It does throw an exception with the message e.g. “Hmm 10.222.287 != 20.000.000” and does never finish. The code does fail because the assumption that Counter++ is an atomic operation is wrong. The ++ operator is just a shortcut for Counter = Counter + 1 This does involve reading the counter from a memory location into the CPU, incrementing value on the CPU and writing the new value back to the memory location. When we do look at the generated assembly code we will see only inc dword ptr [ecx+10h] which is only one instruction. Yes it is one instruction but it is not atomic. All modern CPUs have several layers of caches (L1,L2,L3) which try to hide the fact how slow actual main memory accesses are. Since cache is just another word for redundant copy it can happen that one CPU does read a value from main memory into the cache, modifies it and write it back to the main memory. The problem is that at least the L1 cache is not shared between CPUs so it can happen that one CPU does make changes to values which did change in meantime in the main memory. From the exception you can see we did increment the value 20 million times but half of the changes were lost because we did overwrite the already changed value from the other thread. This is a very common case and people do learn to protect their  data with proper locking.   void Intermediate() { var time = Stopwatch.StartNew(); Action acc = ThreadWorkMethod_Intermediate; var ar1 = acc.BeginInvoke(null, null); var ar2 = acc.BeginInvoke(null, null); ar1.AsyncWaitHandle.WaitOne(); ar2.AsyncWaitHandle.WaitOne(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Intermediate did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Intermediate() { for (int i = 0; i < Increments; i++) { lock (this) { Counter++; } } } This is better and does use the .NET Threadpool to get rid of manual thread management. It does give the expected result but it can result in deadlocks because you do lock on this. This is in general a bad idea since it can lead to deadlocks when other threads use your class instance as lock object. It is therefore recommended to create a private object as lock object to ensure that nobody else can lock your lock object. When you read more about threading you will read about lock free algorithms. They are nice and can improve performance quite a lot but you need to pay close attention to the CLR memory model. It does make quite weak guarantees in general but it can still work because your CPU architecture does give you more invariants than the CLR memory model. For a simple counter there is an easy lock free alternative present with the Interlocked class in .NET. As a general rule you should not try to write lock free algos since most likely you will fail to get it right on all CPU architectures. void Experienced() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); t1.Wait(); t2.Wait(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Experienced did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Experienced() { for (int i = 0; i < Increments; i++) { Interlocked.Increment(ref Counter); } } Since time does move forward we do not use threads explicitly anymore but the much nicer Task abstraction which was introduced with .NET 4 at 2010. It is educational to look at the generated assembly code. The Interlocked.Increment method must be called which does wondrous things right? Lets see: lock inc dword ptr [eax] The first thing to note that there is no method call at all. Why? Because the JIT compiler does know very well about CPU intrinsic functions. Atomic operations which do lock the memory bus to prevent other processors to read stale values are such things. Second: This is the same increment call prefixed with a lock instruction. The only reason for the existence of the Interlocked class is that the JIT compiler can compile it to the matching CPU intrinsic functions which can not only increment by one but can also do an add, exchange and a combined compare and exchange operation. But be warned that the correct usage of its methods can be tricky. If you try to be clever and look a the generated IL code and try to reason about its efficiency you will fail. Only the generated machine code counts. Is this the best code we can write? Perhaps. It is nice and clean. But can we make it any faster? Lets see how good we are doing currently. Level Time in s IJustLearnedToUseThreads Flawed Code Intermediate 1,5 (lock) Experienced 0,3 (Interlocked.Increment) Master 0,1 (1,0 for int[2]) That lock free thing is really a nice thing. But if you read more about CPU cache, cache coherency, false sharing you can do even better. int[] Counters = new int[12]; // Cache line size is 64 bytes on my machine with an 8 way associative cache try for yourself e.g. 64 on more modern CPUs void Master() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Master, 0); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Master, Counters.Length - 1); t1.Wait(); t2.Wait(); Counter = Counters[0] + Counters[Counters.Length - 1]; if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Master did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Master(object number) { int index = (int) number; for (int i = 0; i < Increments; i++) { Counters[index]++; } } The key insight here is to use for each core its own value. But if you simply use simply an integer array of two items, one for each core and add the items at the end you will be much slower than the lock free version (factor 3). Each CPU core has its own cache line size which is something in the range of 16-256 bytes. When you do access a value from one location the CPU does not only fetch one value from main memory but a complete cache line (e.g. 16 bytes). This means that you do not pay for the next 15 bytes when you access them. This can lead to dramatic performance improvements and non obvious code which is faster although it does have many more memory reads than another algorithm. So what have we done here? We have started with correct code but it was lacking knowledge how to use the .NET Base Class Libraries optimally. Then we did try to get fancy and used threads for the first time and failed. Our next try was better but it still had non obvious issues (lock object exposed to the outside). Knowledge has increased further and we have found a lock free version of our counter which is a nice and clean way which is a perfectly valid solution. The last example is only here to show you how you can get most out of threading by paying close attention to your used data structures and CPU cache coherency. Although we are working in a virtual execution environment in a high level language with automatic memory management it does pay off to know the details down to the assembly level. Only if you continue to learn and to dig deeper you can come up with solutions no one else was even considering. I have studied particle physics which does help at the digging deeper part. Have you ever tried to solve Quantum Chromodynamics equations? Compared to that the rest must be easy ;-). Although I am no longer working in the Science field I take pride in discovering non obvious things. This can be a very hard to find bug or a new way to restructure data to make something 10 times faster. Now I need to get some sleep ….

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  • SQL SERVER – Installing AdventureWorks for SQL Server 2011

    - by pinaldave
    I just began with SQL Server 2011 Denali CTP1. The very first thing, I realized that there is no AdventureWorks Sample Database available for Denali. I quickly searched online and reached to Microsoft documentations where it provides information of the how to install (restore) AdventureWorks for SQL Server 2011 for Denali. Download the AdventureWorks from here. Run following script (replace your path of mdf file. CREATE DATABASE AdventureWorks2008R2 ON (FILENAME = 'C:\SQL 11 CTP1\CTP1\AdventureWorks2008R2_Data.mdf') FOR ATTACH_REBUILD_LOG ; When you run above script it will give you following message and you are DONE! File activation failure. The physical file name "C:\Program Files\Microsoft SQL Server\MSSQL11.MSSQLSERVER\MSSQL\DATA\AdventureWorks2008R2_Log.ldf" may be incorrect. New log file 'C:\SQL 11 CTP1\CTP1\AdventureWorks2008R2_log.ldf' was created. Converting database 'AdventureWorks2008R2' from version 679 to the current version 684. Database 'AdventureWorks2008R2' running the upgrade step from version 679 to version 680. Database 'AdventureWorks2008R2' running the upgrade step from version 680 to version 681. Database 'AdventureWorks2008R2' running the upgrade step from version 681 to version 682. Database 'AdventureWorks2008R2' running the upgrade step from version 682 to version 683. Database 'AdventureWorks2008R2' running the upgrade step from version 683 to version 684. I will soon write my experience about Denali. However, SQL Server Management Studio more started to look a like Visual Studio. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Backup and Restore, SQL Query, SQL Scripts, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology

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  • Why do apache2 upgrades remove and not re-install libapache2-mod-php5?

    - by nutznboltz
    We repeatedly see that when an apache2 update arrives and is installed it causes the libapache2-mod-php5 package to be removed and does not subsequently re-install it automatically. We must subsequently re-install the libapache2-mod-php5 manually in order to restore functionality to our web server. Please see the following github gist, it is a contiguous section of our server's dpkg.log showing the November 14, 2011 update to apache2: https://gist.github.com/1368361 it includes 2011-11-14 11:22:18 remove libapache2-mod-php5 5.3.2-1ubuntu4.10 5.3.2-1ubuntu4.10 Is this a known issue? Do other people see this too? I could not find any launchpad bug reports about it. Platform details: $ lsb_release -ds Ubuntu 10.04.3 LTS $ uname -srvm Linux 2.6.38-12-virtual #51~lucid1-Ubuntu SMP Thu Sep 29 20:27:50 UTC 2011 x86_64 $ dpkg -l | awk '/ii.*apache/ {print $2 " " $3 }' apache2 2.2.14-5ubuntu8.7 apache2-mpm-prefork 2.2.14-5ubuntu8.7 apache2-utils 2.2.14-5ubuntu8.7 apache2.2-bin 2.2.14-5ubuntu8.7 apache2.2-common 2.2.14-5ubuntu8.7 libapache2-mod-authnz-external 3.2.4-2+squeeze1build0.10.04.1 libapache2-mod-php5 5.3.2-1ubuntu4.10 Thanks At a high-level the update process looks like: package package_name do action :upgrade case node[:platform] when 'centos', 'redhat', 'scientific' options '--disableplugin=fastestmirror' when 'ubuntu' options '-o Dpkg::Options::="--force-confdef" -o Dpkg::Options::="--force-confold"' end end But at a lower level def install_package(name, version) run_command_with_systems_locale( :command = "apt-get -q -y#{expand_options(@new_resource.options)} install #{name}=#{version}", :environment = { "DEBIAN_FRONTEND" = "noninteractive" } ) end def upgrade_package(name, version) install_package(name, version) end So Chef is using "install" to do "update". This sort of moves the question around to "how does apt-get safe-upgrade" remember to re-install libapache-mod-php5? The exact sequence of packages that triggered this was: apache2 apache2-mpm-prefork apache2-mpm-worker apache2-utils apache2.2-bin apache2.2-common But the code is attempting to run checks to make sure the packages in that list are installed already before attempting to "upgrade" them. case node[:platform] when 'debian', 'centos', 'fedora', 'redhat', 'scientific', 'ubuntu' # first primitive way is to define the updates in the recipe # data bags will be used later %w/ apache2 apache2-mpm-prefork apache2-mpm-worker apache2-utils apache2.2-bin apache2.2-common /.each{ |package_name| Chef::Log.debug("is #{package_name} among local packages available for changes?") next unless node[:packages][:changes].keys.include?(package_name) Chef::Log.debug("is #{package_name} available for upgrade?") next unless node[:packages][:changes][package_name][:action] == 'upgrade' package package_name do action :upgrade case node[:platform] when 'centos', 'redhat', 'scientific' options '--disableplugin=fastestmirror' when 'ubuntu' options '-o Dpkg::Options::="--force-confdef" -o Dpkg::Options::="--force-confold"' end end tag('upgraded') } # after upgrading everything, run yum cache updater if tagged?('upgraded') # Remove old orphaned dependencies and kernel images and kernel headers etc. # Remove cached deb files. case node[:platform] when 'ubuntu' execute 'apt-get -y autoremove' execute 'apt-get clean' # Re-check what updates are available soon. when 'centos', 'fedora', 'redhat', 'scientific' node[:packages][:last_time_we_looked_at_yum] = 0 end untag('upgraded') end end But it's clear that it fails since the dpkg.log has 2011-11-14 11:22:25 install apache2-mpm-worker 2.2.14-5ubuntu8.7 on a system which does not currently have apache2-mpm-worker. I will have to discuss this with the author, thanks again.

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  • How to solve out of memory exception error in Entity FramWork?

    - by programmerist
    Hello; these below codes give whole data of my Rehber datas. But if i want to show web page via Gridview send me out of memory exception error. GenoTip.BAL: public static List<Rehber> GetAllDataOfRehber() { using (GenoTipSatisEntities genSatisCtx = new GenoTipSatisEntities()) { ObjectQuery<Rehber> rehber = genSatisCtx.Rehber; return rehber.ToList(); } } if i bind data directly dummy gridview like that no problem occures every thing is great!!! <asp:GridView ID="gwRehber" runat="server"> </asp:GridView> if above codes send data to Satis.aspx page: using GenoTip.BAL; namespace GenoTip.Web.ContentPages.Satis { public partial class Satis : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { gwRehber.DataSource = SatisServices.GetAllDataOfRehber(); gwRehber.DataBind(); //gwRehber.Columns[0].Visible = false; } } } } but i rearranged my gridview send me out of memory exception!!!! i need this arrangenment to show deta!!! <asp:GridView ID="gwRehber" runat="server"> <Columns> <%-- <asp:TemplateField> <ItemTemplate> <asp:Button runat="server" ID="btnID" CommandName="select" CommandArgument='<%# Eval("ID") %>' Text="Seç" /> </ItemTemplate> </asp:TemplateField>--%> <asp:BoundField DataField="Ad" HeaderText="Ad" /> <asp:BoundField DataField="BireyID" HeaderText="BireyID" Visible="false" /> <asp:BoundField DataField="Degistiren" HeaderText="Degistiren" /> <asp:BoundField DataField="EklemeTarihi" HeaderText="EklemeTarihi" /> <asp:BoundField DataField="DegistirmeTarihi" HeaderText="Degistirme Tarihi" Visible="false" /> <asp:BoundField DataField="Ekleyen" HeaderText="Ekleyen" /> <asp:BoundField DataField="ID" HeaderText="ID" Visible="false" /> <asp:BoundField DataField="Imza" HeaderText="Imza" /> <asp:BoundField DataField="KurumID" HeaderText="KurumID" Visible="false" /> </Columns> </asp:GridView> Error Detail : [OutOfMemoryException: 'System.OutOfMemoryException' türünde özel durum olusturuldu.] System.String.GetStringForStringBuilder(String value, Int32 startIndex, Int32 length, Int32 capacity) +29 System.Convert.ToBase64String(Byte[] inArray, Int32 offset, Int32 length, Base64FormattingOptions options) +146 System.Web.UI.ObjectStateFormatter.Serialize(Object stateGraph) +183 System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Serialize(Object state) +4 System.Web.UI.Util.SerializeWithAssert(IStateFormatter formatter, Object stateGraph) +37 System.Web.UI.HiddenFieldPageStatePersister.Save() +79 System.Web.UI.Page.SavePageStateToPersistenceMedium(Object state) +105 System.Web.UI.Page.SaveAllState() +236 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1099

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  • Windows Updates Fails Server 2008 0x80070490

    - by Mark Robinson
    I have a server with Windows Server 2008 Standard x64 Edition installed. This has been installed and running for several months and I have been able to successfully install previous Windows Updates. I have two pending updates that fail to install. (KB967723) Security update for Windows Server 2008 x64 Edition (KB976098) Update for Windows Server 2008 x64 Edition Fails with Error code: 80070490 Followed this off Microsoft support site, which basically says to repair Windows with the install DVD. When I get to the step to select upgrade I get the following error. Upgrade has been disabled. The upgrade cannot be started. To upgrade, cancel the installation and then choose to upgrade to a version of windows that is more recent then the version you are currently running. So basically feel like I've hit a dead end with out doing a complete reinstall. Any ideas ?

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