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• Detecting source of memory usage on a Linux box

  - by apeace

  I have a toy Linux box with 256mb RAM running Ubuntu 10.04.1 LTS. Here is the output of free -m: total used free shared buffers cached Mem: 245 122 122 0 19 64 -/+ buffers/cache: 38 206 Swap: 511 0 511 Unless I'm reading this wrong, 122mb is being used and only 84mb of that is disk cache. Here are all processes I'm running sorted by memory usage (ps -eo pmem,pcpu,rss,vsize,args | sort -k 1 -r): %MEM %CPU RSS VSZ COMMAND 5.0 0.0 12648 633140 node /home/node/main/sites.js 1.5 0.0 3884 251736 /usr/sbin/console-kit-daemon --no-daemon 1.3 0.0 3328 77108 sshd: apeace [priv] 0.9 0.0 2344 19624 -bash 0.7 0.0 1776 23620 /sbin/init 0.6 0.0 1624 77108 sshd: apeace@pts/0 0.6 0.0 1544 9940 redis-server /etc/redis/redis.conf 0.6 0.0 1524 25848 /usr/sbin/ntpd -p /var/run/ntpd.pid -g -u 103:105 0.5 0.0 1324 119880 rsyslogd -c4 0.4 0.0 1084 49308 /usr/sbin/sshd 0.4 0.0 1028 44376 /usr/sbin/exim4 -bd -q30m 0.3 0.0 904 6876 ps -eo pmem,pcpu,rss,vsize,args 0.3 0.0 888 21124 cron 0.3 0.0 868 23472 dbus-daemon --system --fork 0.2 0.0 732 19624 -bash 0.2 0.0 628 6128 /sbin/getty -8 38400 tty1 0.2 0.0 628 16952 upstart-udev-bridge --daemon 0.2 0.0 564 16800 udevd --daemon 0.2 0.0 552 16796 udevd --daemon 0.2 0.0 548 16796 udevd --daemon 0.0 0.0 0 0 [xenwatch] 0.0 0.0 0 0 [xenbus] 0.0 0.0 0 0 [sync_supers] 0.0 0.0 0 0 [netns] 0.0 0.0 0 0 [migration/3] 0.0 0.0 0 0 [migration/2] 0.0 0.0 0 0 [migration/1] 0.0 0.0 0 0 [migration/0] 0.0 0.0 0 0 [kthreadd] 0.0 0.0 0 0 [kswapd0] 0.0 0.0 0 0 [kstriped] 0.0 0.0 0 0 [ksoftirqd/3] 0.0 0.0 0 0 [ksoftirqd/2] 0.0 0.0 0 0 [ksoftirqd/1] 0.0 0.0 0 0 [ksoftirqd/0] 0.0 0.0 0 0 [ksnapd] 0.0 0.0 0 0 [kseriod] 0.0 0.0 0 0 [kjournald] 0.0 0.0 0 0 [khvcd] 0.0 0.0 0 0 [khelper] 0.0 0.0 0 0 [kblockd/3] 0.0 0.0 0 0 [kblockd/2] 0.0 0.0 0 0 [kblockd/1] 0.0 0.0 0 0 [kblockd/0] 0.0 0.0 0 0 [flush-202:1] 0.0 0.0 0 0 [events/3] 0.0 0.0 0 0 [events/2] 0.0 0.0 0 0 [events/1] 0.0 0.0 0 0 [events/0] 0.0 0.0 0 0 [crypto/3] 0.0 0.0 0 0 [crypto/2] 0.0 0.0 0 0 [crypto/1] 0.0 0.0 0 0 [crypto/0] 0.0 0.0 0 0 [cpuset] 0.0 0.0 0 0 [bdi-default] 0.0 0.0 0 0 [async/mgr] 0.0 0.0 0 0 [aio/3] 0.0 0.0 0 0 [aio/2] 0.0 0.0 0 0 [aio/1] 0.0 0.0 0 0 [aio/0] Now, I know that ps is not the best for viewing process memory usage, but that's because it tends to report more memory than is actually being used...meaning no matter how you look at it all my processes combined shouldn't be using near 122mb, even if you account for the disk cache. What's more, memory usage is growing all the time. I've had to restart my server once a week, because once my 256mb fills up it starts swapping, which it wouldn't do just for disk cache. Shouldn't there be some way for me to see the culprit?! I'm new to server admin, so please if there's something obvious I'm overlooking point it out to me. Just for good measure, the output of cat /proc/meminfo: MemTotal: 251140 kB MemFree: 124604 kB Buffers: 20536 kB Cached: 66136 kB SwapCached: 0 kB Active: 65004 kB Inactive: 37576 kB Active(anon): 15932 kB Inactive(anon): 164 kB Active(file): 49072 kB Inactive(file): 37412 kB Unevictable: 0 kB Mlocked: 0 kB SwapTotal: 524284 kB SwapFree: 524284 kB Dirty: 8 kB Writeback: 0 kB AnonPages: 15916 kB Mapped: 10668 kB Shmem: 188 kB Slab: 18604 kB SReclaimable: 10088 kB SUnreclaim: 8516 kB KernelStack: 536 kB PageTables: 1444 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 649852 kB Committed_AS: 64224 kB VmallocTotal: 34359738367 kB VmallocUsed: 752 kB VmallocChunk: 34359737600 kB DirectMap4k: 262144 kB DirectMap2M: 0 kB EDIT: I had misinterpreted the meaning of free -m at first. But even so: the important thing is that my OS eventually begins to use swap memory if I don't restart my server, which disk caching wouldn't do. So where do I look to see what is using all this memory?

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• strange data annotations issue in MVC 2

  - by femi

  Hello, I came across something strange when creating an edit form with MVC 2. i realised that my error messages come up on form sumission even when i have filled ut valid data! i am using a buddy class which i have configured correctly ( i know that cos i can see my custom errors). Here is the code from the viewmodel that generates this; <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<TG_Careers.Models.Applicant>" %> <script src="/Scripts/MicrosoftAjax.js" type="text/javascript"></script> <script src="/Scripts/MicrosoftMvcAjax.js" type="text/javascript"></script> <script src="/Scripts/MicrosoftMvcValidation.js" type="text/javascript"></script> <%= Html.ValidationSummary() %> <% Html.EnableClientValidation(); %> <% using (Html.BeginForm()) {%> <div class="confirm-module"> <table cellpadding="4" cellspacing="2"> <tr> <td><%= Html.LabelFor(model => model.FirstName) %> </td> <td><%= Html.EditorFor(model => model.FirstName) %></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.FirstName) %></td> </tr> <tr> <td><%= Html.LabelFor(model => model.MiddleName) %></td> <td><%= Html.EditorFor(model => model.MiddleName) %></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.MiddleName) %></td> </tr> <tr> <td><%= Html.LabelFor(model => model.LastName) %></td> <td><%= Html.EditorFor(model => model.LastName) %></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.LastName) %></td> </tr> <tr> <td><%= Html.LabelFor(model => model.Gender) %></td> <td><%= Html.EditorFor(model => model.Gender) %></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.Gender) %></td> </tr> <tr> <td><%= Html.LabelFor(model => model.MaritalStatus) %></td> <td> <%= Html.EditorFor(model => model.MaritalStatus) %></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.MaritalStatus) %></td> </tr> <tr> <td><%= Html.LabelFor(model => model.DateOfBirth) %></td> <td><%= Html.EditorFor(model => model.DateOfBirth) %></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.DateOfBirth) %></td> </tr> <tr> <td><%= Html.LabelFor(model => model.Address) %></td> <td><%= Html.EditorFor(model => model.Address) %></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.Address) %></td> </tr> <tr> <td><%= Html.LabelFor(model => model.City) %></td> <td><%= Html.EditorFor(model => model.City) %></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.City) %></td> </tr> <tr> <td><%= Html.LabelFor(model => model.State) %></td> <td><%= Html.EditorFor(model => model.State) %></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.State) %></td> </tr> <tr> <td><%= Html.LabelFor(model => model.StateOfOriginID) %></td> <td><%= Html.DropDownList("StateOfOriginID", new SelectList(ViewData["States"] as IEnumerable, "StateID", "Name", Model.StateOfOriginID))%></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.StateOfOriginID) %></td> </tr> <tr> <td><%= Html.LabelFor(model => model.CompletedNYSC) %></td> <td><%= Html.EditorFor(model => model.CompletedNYSC) %></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.CompletedNYSC) %></td> </tr> <tr> <td><%= Html.LabelFor(model => model.YearsOfExperience) %></td> <td><%= Html.EditorFor(model => model.YearsOfExperience) %></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.YearsOfExperience) %></td> </tr> <tr> <td><%= Html.LabelFor(model => model.MobilePhone) %></td> <td><%= Html.EditorFor(model => model.MobilePhone) %></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.MobilePhone) %></td> </tr> <tr> <td><%= Html.LabelFor(model => model.DayPhone) %></td> <td> <%= Html.EditorFor(model => model.DayPhone) %></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.DayPhone) %></td> </tr> <tr> <td><%= Html.LabelFor(model => model.CVFileName) %></td> <td><%= Html.EditorFor(model => model.CVFileName) %></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.CVFileName) %></td> </tr> <tr> <td><%= Html.LabelFor(model => model.CurrentPosition) %></td> <td><%= Html.EditorFor(model => model.CurrentPosition) %></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.CurrentPosition) %></td> </tr> <tr> <td><%= Html.LabelFor(model => model.EmploymentCommenced) %></td> <td><%= Html.EditorFor(model => model.EmploymentCommenced) %></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.EmploymentCommenced) %></td> </tr> <tr> <td><%= Html.LabelFor(model => model.DateofTakingupCurrentPosition) %></td> <td><%= Html.EditorFor(model => model.DateofTakingupCurrentPosition) %></td> </tr> <tr> <td colspan="2"><%= Html.ValidationMessageFor(model => model.DateofTakingupCurrentPosition) %></td> </tr> <tr> <td>&nbsp;</td> <td>&nbsp;</td> </tr> <tr> <td colspan="2">&nbsp;</td> </tr> </table> <p> <input type="submit" value="Save Profile Details" /> </p> </div> <% } %> Any ideas on this one please? Thanks

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• Windows7 issue in mutli- tasking and memory

  - by Nitesh

  I seeming some problem in my windows OS recently, let me first say my system configuration. processor - Intel(R) Core(TM)2 Quad CPU Q8400 @ 2.66 GHz Installed memory (RAM) - 4.00 GB (3.00 GB usable) System type - 32 bit operating system I am using two OS in this system, first one is Windows7 and the other is centOS. Well, I am using this from a long time there was no problem , and all of a sudden since from couple weeks I am facing problems in my Windows7 OS. In windows7 i was nearing using multiple jobs almost every time i log in, there was no problem but now i don't no what happen I am not able to do multiple jobs at same time. For example- 1 I am now not able to listen to music in windows media player and view photo's. All of a sudden the system stops working and does not respond and then respond after 5mins and the music get played where it got stopped after 5 mins. 2 When i start browersing internet it hangs all of sudden and doesn't respond for 2 or 3 mins and gets loading. I mean it just happens for every operation i do in the system. Even now typing was also difficult, it gets hanged very frequently even though i am doing single task. I have never come across this kind of problem before. So the first thing i did was to see the useage of the processor and the memory. Well, i thick the useage of the processor was fine, for single task the useage was some where around 3 to 5%. Well, it was something weird i found in the memory, in spite of no task that i was running it was using somewhere around 34 to 41% of memory. So i opened the task manager and click on resource monitor in performance tab. And in the memory section of the monitoring tool i found the usage of my RAM, it was something like this. Hardware reserved - 1029 MB In Use - 1430 MB Modified - 49 MB Standby - 1566 MB free - 22 MB And i could also see Available 1588 MB Cached 1615 MB Total 3067 MB Installed 4096 MB well, this if all i could find out and i have no idea why my computer is acting so weird all of a sudden and the performance problem is growing day by day and i also don't know if there is problem in Bios, i have let it for default settings from long time. please help me and Thank you in advance for reading this and helping me.

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• Memory upgrade to 8GB on unibody MacBook

  - by dlamblin

  I bought the 13" unibody MacBook one month prior to it's upgrade to become the new improved 13" unibody MacBook Pro (with unopenable battery compartment, extra 3 hours of battery life, more color gammut, SD slot, firewire 800 port, and a new 8Gb memory limit). My MacBook says it is limited to 4GB of DDR3 1066mhz memory, in 2 SO-DIMMs. But that was written back when you couldn't get 2 4GB SO-DIMMs. Now that you can get them, the very similar MacBook Pro is shipping with 4GB standard, and can be upgraded to 8GB. I've asked (Apple reps), and I'm repeatedly told that my model cannot be upgraded to 8. When I ask for the reason they alway say: "Because that's the published limit at the time your mac was built." I find this unconvincing. If they said: "Because the memory controller in the chipset is limited to 4GB, despite being seemingly identical to the memory controller in the same chipset newest MacBook model," then I'd just take their word for it. Has anyone tried it, or found any research as to whether two 4GB DDR3 1066mhz SO-DIMMs can be installed in the unibody MacBook without FireWire?

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• dhclient requests filling memory?

  - by shanethehat

  Dammit Jim, I'm a web developer, not a sys admin. With that out of the way, my client's has a CentOS server (6.2) that is only serving a single Magento site (and the associated MySQL server) and it is frequently running out of memory, despite the site only currently being open to 5 users. I'm investigating the logs to try to figure out why the memory usage is so high, but I don't really know what I'm looking at. It seems that there are a lot of entries in /var/log/messages concerning DHCP requests, approximately one every 15 seconds, that look like this: Apr 7 14:23:06 s15940039 dhclient[815]: DHCPREQUEST on eth0 to 172.30.102.85 port 67 (xid=0x6b5cd2a7) Is this normal? I don't see anything else in here that I don't recognise, but then I'm not sure I'd know the problem if I did see it. 4 days ago the server ran out of memory completely and locked up, requiring a restart. The DHCP messages did not start up again for 23 hours, but then carried on as before. I have read this question which describes the same issue, but in my case a fresh DHCP lease does not ever seem to be issued. Is this something I should push back to the hosting provider, or have I not yet found the source of the memory problem?

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• What causes memory fragmentation in .NET

  - by Matt

  I am using Red Gates ANTS memory profiler to debug a memory leak. It keeps warning me that: Memory Fragmentation may be causing .NET to reserver too much free memory. or Memory Fragmentation is affecting the size of the largest object that can be allocated Because I have OCD, this problem must be resolved. What are some standard coding practices that help avoid memory fragmentation. Can you defragment it through some .NET methods? Would it even help?

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• Analyzing Memory Usage: Java vs C++ Negligible?

  - by Anthony

  How does the memory usage of an integer object written in Java compare\contrast with the memory usage of a integer object written in C++? Is the difference negligible? No difference? A big difference? I'm guessing it's the same because an int is an int regardless of the language (?) The reason why I asked this is because I was reading about the importance of knowing when a program's memory requirements will prevent the programmer from solving a given problem. What fascinated me is the amount of memory required for creating a single Java object. Take for example, an integer object. Correct me if I'm wrong but a Java integer object requires 24 bytes of memory: 4 bytes for its int instance variable 16 bytes of overhead (reference to the object's class, garbage collection info & synchronization info) 4 bytes of padding As another example, a Java array (which is implemented as an object) requires 48+bytes: 24 bytes of header info 16 bytes of object overhead 4 bytes for length 4 bytes for padding plus the memory needed to store the values How do these memory usages compare with the same code written in C++? I used to be oblivious about the memory usage of the C++ and Java programs I wrote, but now that I'm beginning to learn about algorithms, I'm having a greater appreciation for the computer's resources.

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• Sun T5120: Memory issue with 8GB DIMMs, "Unsupported memory configuration"

  - by watain

  I'm trying to upgrade RAM in a Sun T5120 server, replacing 2GB (Sun P/N: 501-7953-01) with 8GB DIMMs (Sun P/N: 511-1262-01). When bringing up the host system, I get the following errors on the ILOM: -> show faulty Target | Property | Value --------------------+------------------------+--------------------------------- /SP/faultmgmt/0 | fru | /SYS/MB /SP/faultmgmt/0/ | timestamp | Dec 14 15:29:42 faults/0 | | /SP/faultmgmt/0/ | sp_detected_fault | /SYS/MB/CMP0/MCU3 Forced fail faults/0 | | (IBIST) /SP/faultmgmt/0/ | timestamp | Dec 14 15:29:28 faults/1 | | /SP/faultmgmt/0/ | sp_detected_fault | /SYS/MB/CMP0/MCU2 Forced fail faults/1 | | (IBIST) /SP/faultmgmt/0/ | timestamp | Dec 14 15:29:13 faults/2 | | /SP/faultmgmt/0/ | sp_detected_fault | /SYS/MB/CMP0/MCU1 Forced fail faults/2 | | (IBIST) /SP/faultmgmt/0/ | timestamp | Dec 14 15:28:59 faults/3 | | /SP/faultmgmt/0/ | sp_detected_fault | /SYS/MB/CMP0/MCU0 Forced fail faults/3 | | (IBIST) /SP/faultmgmt/1 | fru | /SYS /SP/faultmgmt/1/ | timestamp | Dec 14 15:29:42 faults/0 | | /SP/faultmgmt/1/ | sp_detected_fault | Dec 14 15:29:42 ERROR: faults/0 | | Unsupported memory | | configuration As you can see, the only error message I get is "Unsupported memory configuration". Note that I'm absolutely sure that I placed in the DIMMs in the correct slots. Might this issue be related to the Voltage of the DIMMs? Any suggestions on how to trouble-shoot this issue? This issue seems to be similar to the one explained at "Inserted disabled" while upgrading Sun Sparc t5120 memory. However the given link http://docs.sun.com/source/820-4445-10/chapter1.html seems to point to an inexistent page...

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• iPhone - Memory Management - Using Leaks tool and getting some bizarre readings.

  - by Robert

  Hey all, putting the finishing touches on a project of mine so I figured I would run through it and see if and where I had any memory leaks. Found and fixed most of them but there are a couple of things regarding the memory leaks and object alloc that I am confused about. 1) There are 2 memory leaks that do not show me as responsible. There are 8 leaks attributed to AudioToolbox with the function being RegisterEmbeddedAudioCodecs(). This accounts for about 1.5 kb of leaks. The other one is detected immediately when the app begins. Core Graphics is responsible with the extra info being open_handle_to_dylib_path. For the audio leak I have looked over my audio code and to me it seems ok. self.musicPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:songFilePath] error:NULL]; [musicPlayer prepareToPlay]; [musicPlayer play] is called later on in a function. 2) Is it normal for there to be a spike in Object Allocation whenever a new view or controller is presented? My total memory usage is very, very low except for whenever I present a view controller. It spikes then immediately goes back down. I am guessing that this is just the phone handling all the information for switching or something. Blegh. Wall of text. Thanks in advance to anyone who helps! =)

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• Out of memory Problem

  - by Sunil

  I'm running a C++ program in Ubuntu 10.04 (32-bit system architecture). If I calculate the amount of memory that my program uses, it comes up to 800MB. I have a 4GB RAM in place. But still before the program even finishes it throws an out of memory exception. Why is that happening ? Is it because of the structure of the memory or implementation problems or what could possibly trigger this issue ? I've had seen this problem quite a number of times before but never understood the reason behind it. Have any of you handled this case before ?

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• Munin fills server memory

  - by danilo

  In the last weeks, it happened several times to me that my vserver (Debian Lenny) was out of RAM (500M) and therefore wasn't able to run apache anymore. When looking at the processes with top, I saw that there were many open munin-limits and munin-cron processes that consumed most of the memory. My guess would be that sometimes Apache temporarily needs more memory, which prevents munin-cron from running. And if munin-cron isn't able to stop itself, it would fill the memory until nothing is left. I don't know whether this guess is true, but could maybe someone know what the problem is and how to prevent it? If necessary I'll remove munin, but I'd prefer to keep it running.

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• How is dynamic memory allocation handled when extreme reliability is required?

  - by sharptooth

  Looks like dynamic memory allocation without garbage collection is a way to disaster. Dangling pointers there, memory leaks here. Very easy to plant an error that is sometimes hard to find and that has severe consequences. How are these problems addressed when mission-critical programs are written? I mean if I write a program that controls a spaceship like Voyager 1 that has to run for years and leave a smallest leak that leak can accumulate and halt the program sooner or later and when that happens it translates into epic fail. How is dynamic memory allocation handled when a program needs to be extremely reliable?

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• ASP.NET MVC Postbacks and HtmlHelper Controls ignoring Model Changes

  - by Rick Strahl

  So here's a binding behavior in ASP.NET MVC that I didn't really get until today: HtmlHelpers controls (like .TextBoxFor() etc.) don't bind to model values on Postback, but rather get their value directly out of the POST buffer from ModelState. Effectively it looks like you can't change the display value of a control via model value updates on a Postback operation. To demonstrate here's an example. I have a small section in a document where I display an editable email address: This is what the form displays on a GET operation and as expected I get the email value displayed in both the textbox and plain value display below, which reflects the value in the mode. I added a plain text value to demonstrate the model value compared to what's rendered in the textbox. The relevant markup is the email address which needs to be manipulated via the model in the Controller code. Here's the Razor markup: <div class="fieldcontainer"> <label> Email: &nbsp; <small>(username and <a href="http://gravatar.com">Gravatar</a> image)</small> </label> <div> @Html.TextBoxFor( mod=> mod.User.Email, new {type="email",@class="inputfield"}) @Model.User.Email </div> </div>   So, I have this form and the user can change their email address. On postback the Post controller code then asks the business layer whether the change is allowed. If it's not I want to reset the email address back to the old value which exists in the database and was previously store. The obvious thing to do would be to modify the model. Here's the Controller logic block that deals with that:// did user change email? if (!string.IsNullOrEmpty(oldEmail) && user.Email != oldEmail) { if (userBus.DoesEmailExist(user.Email)) { userBus.ValidationErrors.Add("New email address exists already. Please…"); user.Email = oldEmail; } else // allow email change but require verification by forcing a login user.IsVerified = false; }… model.user = user; return View(model); The logic is straight forward - if the new email address is not valid because it already exists I don't want to display the new email address the user entered, but rather the old one. To do this I change the value on the model which effectively does this:model.user.Email = oldEmail; return View(model); So when I press the Save button after entering in my new email address ([email protected]) here's what comes back in the rendered view: Notice that the textbox value and the raw displayed model value are different. The TextBox displays the POST value, the raw value displays the actual model value which are different. This means that MVC renders the textbox value from the POST data rather than from the view data when an Http POST is active. Now I don't know about you but this is not the behavior I expected - initially. This behavior effectively means that I cannot modify the contents of the textbox from the Controller code if using HtmlHelpers for binding. Updating the model for display purposes in a POST has in effect - no effect. (Apr. 25, 2012 - edited the post heavily based on comments and more experimentation) What should the behavior be? After getting quite a few comments on this post I quickly realized that the behavior I described above is actually the behavior you'd want in 99% of the binding scenarios. You do want to get the POST values back into your input controls at all times, so that the data displayed on a form for the user matches what they typed. So if an error occurs, the error doesn't mysteriously disappear getting replaced either with a default value or some value that you changed on the model on your own. Makes sense. Still it is a little non-obvious because the way you create the UI elements with MVC, it certainly looks like your are binding to the model value:@Html.TextBoxFor( mod=> mod.User.Email, new {type="email",@class="inputfield",required="required" }) and so unless one understands a little bit about how the model binder works this is easy to trip up. At least it was for me. Even though I'm telling the control which model value to bind to, that model value is only used initially on GET operations. After that ModelState/POST values provide the display value. Workarounds The default behavior should be fine for 99% of binding scenarios. But if you do need fix up values based on your model rather than the default POST values, there are a number of ways that you can work around this. Initially when I ran into this, I couldn't figure out how to set the value using code and so the simplest solution to me was simply to not use the MVC Html Helper for the specific control and explicitly bind the model via HTML markup and @Razor expression: <input type="text" name="User.Email" id="User_Email" value="@Model.User.Email" /> And this produces the right result. This is easy enough to create, but feels a little out of place when using the @Html helpers for everything else. As you can see by the difference in the name and id values, you also are forced to remember the naming conventions that MVC imposes in order for ModelBinding to work properly which is a pain to remember and set manually (name is the same as the property with . syntax, id replaces dots with underlines). Use the ModelState Some of my original confusion came because I didn't understand how the model binder works. The model binder basically maintains ModelState on a postback, which holds a value and binding errors for each of the Post back value submitted on the page that can be mapped to the model. In other words there's one ModelState entry for each bound property of the model. Each ModelState entry contains a value property that holds AttemptedValue and RawValue properties. The AttemptedValue is essentially the POST value retrieved from the form. The RawValue is the value that the model holds. When MVC binds controls like @Html.TextBoxFor() or @Html.TextBox(), it always binds values on a GET operation. On a POST operation however, it'll always used the AttemptedValue to display the control. MVC binds using the ModelState on a POST operation, not the model's value. So, if you want the behavior that I was expecting originally you can actually get it by clearing the ModelState in the controller code:ModelState.Clear(); This clears out all the captured ModelState values, and effectively binds to the model. Note this will produce very similar results - in fact if there are no binding errors you see exactly the same behavior as if binding from ModelState, because the model has been updated from the ModelState already and binding to the updated values most likely produces the same values you would get with POST back values. The big difference though is that any values that couldn't bind - like say putting a string into a numeric field - will now not display back the value the user typed, but the default field value or whatever you changed the model value to. This is the behavior I was actually expecting previously. But - clearing out all values might be a bit heavy handed. You might want to fix up one or two values in a model but rarely would you want the entire model to update from the model. So, you can also clear out individual values on an as needed basis:if (userBus.DoesEmailExist(user.Email)) { userBus.ValidationErrors.Add("New email address exists already. Please…"); user.Email = oldEmail; ModelState.Remove("User.Email"); } This allows you to remove a single value from the ModelState and effectively allows you to replace that value for display from the model. Why? While researching this I came across a post from Microsoft's Brad Wilson who describes the default binding behavior best in a forum post: The reason we use the posted value for editors rather than the model value is that the model may not be able to contain the value that the user typed. Imagine in your "int" editor the user had typed "dog". You want to display an error message which says "dog is not valid", and leave "dog" in the editor field. However, your model is an int: there's no way it can store "dog". So we keep the old value. If you don't want the old values in the editor, clear out the Model State. That's where the old value is stored and pulled from the HTML helpers. There you have it. It's not the most intuitive behavior, but in hindsight this behavior does make some sense even if at first glance it looks like you should be able to update values from the model. The solution of clearing ModelState works and is a reasonable one but you have to know about some of the innards of ModelState and how it actually works to figure that out.© Rick Strahl, West Wind Technologies, 2005-2012Posted in ASP.NET  MVC   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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• Tips on ensuring Model Quality

  - by [email protected]

  Given enough data that represents well the domain and models that reflect exactly the decision being optimized, models usually provide good predictions that ensure lift. Nevertheless, sometimes the modeling situation is less than ideal. In this blog entry we explore the problems found in a few such situations and how to avoid them.1 - The Model does not reflect the problem you are trying to solveFor example, you may be trying to solve the problem: "What product should I recommend to this customer" but your model learns on the problem: "Given that a customer has acquired our products, what is the likelihood for each product". In this case the model you built may be too far of a proxy for the problem you are really trying to solve. What you could do in this case is try to build a model based on the result from recommendations of products to customers. If there is not enough data from actual recommendations, you could use a hybrid approach in which you would use the [bad] proxy model until the recommendation model converges.2 - Data is not predictive enoughIf the inputs are not correlated with the output then the models may be unable to provide good predictions. For example, if the input is the phase of the moon and the weather and the output is what car did the customer buy, there may be no correlations found. In this case you should see a low quality model.The solution in this case is to include more relevant inputs.3 - Not enough cases seenIf the data learned does not include enough cases, at least 200 positive examples for each output, then the quality of recommendations may be low. The obvious solution is to include more data records. If this is not possible, then it may be possible to build a model based on the characteristics of the output choices rather than the choices themselves. For example, instead of using products as output, use the product category, price and brand name, and then combine these models.4 - Output leaking into input giving the false impression of good quality modelsIf the input data in the training includes values that have changed or are available only because the output happened, then you will find some strong correlations between the input and the output, but these strong correlations do not reflect the data that you will have available at decision (prediction) time. For example, if you are building a model to predict whether a web site visitor will succeed in registering, and the input includes the variable DaysSinceRegistration, and you learn when this variable has already been set, you will probably see a big correlation between having a Zero (or one) in this variable and the fact that registration was successful.The solution is to remove these variables from the input or make sure they reflect the value as of the time of decision and not after the result is known. 

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• SQL SERVER – Weekly Series – Memory Lane – #053 – Final Post in Series

  - by Pinal Dave

  It has been a fantastic journey to write memory lane series for an entire year. This series gave me the opportunity to go back and see what I have contributed to this blog throughout the last 7 years. This was indeed fantastic series as this provided me the opportunity to witness how technology has grown throughout the year and how I have progressed in my career while writing this blog post. This series was indeed fantastic experience readers as many joined during the last few years and were not sure what they have missed in recent years. Let us continue with the final episode of the Memory Lane Series. Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2007 Get Current User – Get Logged In User Here is the straight script which list logged in SQL Server users. Disable All Triggers on a Database – Disable All Triggers on All Servers Question : How to disable all the triggers for a database? Additionally, how to disable all the triggers for all servers? For answer execute the script in the blog post. Importance of Master Database for SQL Server Startup I have received following questions many times. I will list all the questions here and answer them together. What is the purpose of Master database? Should our backup Master database? Which database is must have database for SQL Server for startup? Which are the default system database created when SQL Server 2005 is installed for the first time? What happens if Master database is corrupted? Answers to all of the questions are very much related. 2008 DECLARE Multiple Variables in One Statement SQL Server is a great product and it has many features which are very unique to SQL Server. Regarding feature of SQL Server where multiple variable can be declared in one statement, it is absolutely possible to do. 2009 How to Enable Index – How to Disable Index – Incorrect syntax near ‘ENABLE’ Many times I have seen that the index is disabled when there is a large update operation on the table. Bulk insert of very large file updates in any table using SSIS is usually preceded by disabling the index and followed by enabling the index. I have seen many developers running the following query to disable the index. 2010 List of all the Views from Database Many emails I received suggesting that they have hundreds of the view and now have no clue what is going on and how many of them have indexes and how many does not have an index. Some even asked me if there is any way they can get a list of the views with the property of Index along with it. Here is the quick script which does exactly the same. You can also include many other columns from the same view. Minimum Maximum Memory – Server Memory Options I was recently reading about SQL Server Memory Options over here. While reading this one line really caught my attention is minimum value allowed for maximum memory options. The default setting for min server memory is 0, and the default setting for max server memory is 2147483647. The minimum amount of memory you can specify for max server memory is 16 megabytes (MB). 2011 Fundamentals of Columnstore Index There are two kinds of storage in a database. Row Store and Column Store. Row store does exactly as the name suggests – stores rows of data on a page – and column store stores all the data in a column on the same page. These columns are much easier to search – instead of a query searching all the data in an entire row whether the data are relevant or not, column store queries need only to search a much lesser number of the columns. How to Ignore Columnstore Index Usage in Query In summary the question in simple words “How can we ignore using the column store index in selective queries?” Very interesting question – you can use I can understand there may be the cases when the column store index is not ideal and needs to be ignored the same. You can use the query hint IGNORE_NONCLUSTERED_COLUMNSTORE_INDEX to ignore the column store index. The SQL Server Engine will use any other index which is best after ignoring the column store index. 2012 Storing Variable Values in Temporary Array or Temporary List SQL Server does not support arrays or a dynamic length storage mechanism like list. Absolutely there are some clever workarounds and few extra-ordinary solutions but everybody can;t come up with such solution. Additionally, sometime the requirements are very simple that doing extraordinary coding is not required. Here is the simple case. Move Database Files MDF and LDF to Another Location It is not common to keep the Database on the same location where OS is installed. Usually Database files are in SAN, Separate Disk Array or on SSDs. This is done usually for performance reason and manageability perspective. Now the challenges comes up when database which was installed at not preferred default location and needs to move to a different location. Here is the quick tutorial how you can do it. UNION ALL and ORDER BY – How to Order Table Separately While Using UNION ALL If your requirement is such that you want your top and bottom query of the UNION resultset independently sorted but in the same result set you can add an additional static column and order by that column. Let us re-create the same scenario. Copy Data from One Table to Another Table – SQL in Sixty Seconds #031 – Video http://www.youtube.com/watch?v=FVWIA-ACMNo Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Memory Usage for Databases on Linux

  - by Kyle Brandt

  So with free output what we care about with application memory usage is generally the amount of free memory in the -/+ buffers/cache line. What about with database applications such as Oracle, is it important to have a good amount of cached and buffers available for a database to run well with all the IO? If that makes any sense, how do you figure out just how much?

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• Embedded Linux: Memory Fragmentation

  - by waffleman

  In many embedded systems, memory fragmentation is a concern. Particularly, for software that runs for long periods of time (months, years, etc...). For many projects, the solution is to simply not use dynamic memory allocation such as malloc/free and new/delete. Global memory is used whenever possible and memory pools for types that are frequently allocated and deallocated are good strategies to avoid dynamic memory management use. In Embedded Linux how is this addressed? I see many libraries use dynamic memory. Is there mechanism that the OS uses to prevent memory fragmentation? Does it clean up the heap periodically? Or should one avoid using these libraries in an embedded environment?

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• How to store bitmaps in memory?

  - by Geotarget

  I'm working with general purpose image rendering, and high-performance image processing, and so I need to know how to store bitmaps in-memory. (24bpp/32bpp, compressed/raw, etc) I'm not working with 3D graphics or DirectX / OpenGL rendering and so I don't need to use graphics card compatible bitmap formats. My questions: What is the "usual" or "normal" way to store bitmaps in memory? (in C++ engines/projects?) How to store bitmaps for high-performance algorithms, such that read/write times are the fastest? (fixed array? with/without padding? 24-bpp or 32-bpp?) How to store bitmaps for applications handling a lot of bitmap data, to minimize memory usage? (JPEG? or a faster [de]compression algorithm?) Some possible methods: Use a fixed packed 24-bpp or 32-bpp int[] array and simply access pixels using pointer access, all pixels are allocated in one continuous memory chunk (could be 1-10 MB) Use a form of "sparse" data storage so each line of the bitmap is allocated separately, reusing more memory and requiring smaller contiguous memory segments Store bitmaps in its compressed form (PNG, JPG, GIF, etc) and unpack only when its needed, reducing the amount of memory used. Delete the unpacked data if its not used for 10 secs.

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• Recommended formats to store bitmaps in memory?

  - by Geotarget

  I'm working with general purpose image rendering, and high-performance image processing, and so I need to know how to store bitmaps in-memory. (24bpp/32bpp, compressed/raw, etc) I'm not working with 3D graphics or DirectX / OpenGL rendering and so I don't need to use graphics card compatible bitmap formats. My questions: What is the "usual" or "normal" way to store bitmaps in memory? (in C++ engines/projects?) How to store bitmaps for high-performance algorithms, such that read/write times are the fastest? (fixed array? with/without padding? 24-bpp or 32-bpp?) How to store bitmaps for applications handling a lot of bitmap data, to minimize memory usage? (JPEG? or a faster [de]compression algorithm?) Some possible methods: Use a fixed packed 24-bpp or 32-bpp int[] array and simply access pixels using pointer access, all pixels are allocated in one continuous memory chunk (could be 1-10 MB) Use a form of "sparse" data storage so each line of the bitmap is allocated separately, reusing more memory and requiring smaller contiguous memory segments Store bitmaps in its compressed form (PNG, JPG, GIF, etc) and unpack only when its needed, reducing the amount of memory used. Delete the unpacked data if its not used for 10 secs.

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• Finding source of leaking active memory on Mac OS Lion

  - by Tim Kemp

  My activity monitor shows 6GB of active RAM usage: Yet my Real Memory column shows nothing like that amount: (There's another screenful below that, all smaller.) Backing that up, the output from this command (which sums up memory usage of every running process): ps -axm -o "rss,comm" | awk 'BEGIN { s=0;}; {s=s+$1;}; END { printf("%.2f GB\n", (s/1024.0/1024));}' Gives 4.09GB, so it looks to me like 2GB has leaked. I see much wider ranges sometimes, perhaps 2 or 3GB from the ps command and as much as 7 or 8GB of Active usage reported by Activity Monitor. I've tried quitting everything and logging my user out and back in again, but the Active usage is still far higher than the RAM reported by ps and by each process to Activity Monitor. This 2GB of active RAM is basically unrecoverable unless I reboot. Is there any way to a) detect what's leaking and b) get it back? Thanks

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• Memory limiting solutions for greedy applications that can crash OS?

  - by Hooked

  I use my computer for scientific programming. It has a healthy 8GB of RAM and 12GB of swap space. Often, as my problems have gotten larger, I exceed all of the available RAM. Rather than crashing (which would be preferred), it seems Ubuntu starts loading everything into swap, including Unity and any open terminals. If I don't catch a run-away program in time, there is nothing I can do but wait - it takes 4-5 minutes to switch to a command prompt eg. Ctrl-Alt-F2 where I can kill the offending process. Since my own stupidity is out of scope of this forum, how can I prevent Ubuntu from crashing via thrashing when I use up all of the available memory from a single offending program? At-home experiment*! Open a terminal, launch python and if you have numpy installed try this: >>> import numpy >>> [numpy.zeros((10**4, 10**4)) for _ in xrange(50)] * Warning: may have adverse effects, monitor the process via iotop or top to kill it in time. If not, I'll see you after your reboot.

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• Monitor and Control Memory Usage in Google Chrome

  - by Asian Angel

  Do you want to know just how much memory Google Chrome and any installed extensions are using at a given moment? With just a few clicks you can see just what is going on under the hood of your browser. How Much Memory are the Extensions Using? Here is our test browser with a new tab and the Extensions Page open, five enabled extensions, and one disabled at the moment. You can access Chrome’s Task Manager using the Page Menu, going to Developer, and selecting Task manager… Or by right clicking on the Tab Bar and selecting Task manager. There is also a keyboard shortcut (Shift + Esc) available for the “keyboard ninjas”. Sitting idle as shown above here are the stats for our test browser. All of the extensions are sitting there eating memory even though some of them are not available/active for use on our new tab and Extensions Page. Not so good… If the default layout is not to your liking then you can easily modify the information that is available by right clicking and adding/removing extra columns as desired. For our example we added Shared Memory & Private Memory. Using the about:memory Page to View Memory Usage Want even more detail? Type about:memory into the Address Bar and press Enter. Note: You can also access this page by clicking on the Stats for nerds Link in the lower left corner of the Task Manager Window. Focusing on the four distinct areas you can see the exact version of Chrome that is currently installed on your system… View the Memory & Virtual Memory statistics for Chrome… Note: If you have other browsers running at the same time you can view statistics for them here too. See a list of the Processes currently running… And the Memory & Virtual Memory statistics for those processes. The Difference with the Extensions Disabled Just for fun we decided to disable all of the extension in our test browser… The Task Manager Window is looking rather empty now but the memory consumption has definitely seen an improvement. Comparing Memory Usage for Two Extensions with Similar Functions For our next step we decided to compare the memory usage for two extensions with similar functionality. This can be helpful if you are wanting to keep memory consumption trimmed down as much as possible when deciding between similar extensions. First up was Speed Dial”(see our review here). The stats for Speed Dial…quite a change from what was shown above (~3,000 – 6,000 K). Next up was Incredible StartPage (see our review here). Surprisingly both were nearly identical in the amount of memory being used. Purging Memory Perhaps you like the idea of being able to “purge” some of that excess memory consumption. With a simple command switch modification to Chrome’s shortcut(s) you can add a Purge Memory Button to the Task Manager Window as shown below.  Notice the amount of memory being consumed at the moment… Note: The tutorial for adding the command switch can be found here. One quick click and there is a noticeable drop in memory consumption. Conclusion We hope that our examples here will prove useful to you in managing the memory consumption in your own Google Chrome installation. If you have a computer with limited resources every little bit definitely helps out. Similar Articles Productive Geek Tips Stupid Geek Tricks: Compare Your Browser’s Memory Usage with Google ChromeMonitor CPU, Memory, and Disk IO In Windows 7 with Taskbar MetersFix for Firefox memory leak on WindowsHow to Purge Memory in Google ChromeHow to Make Google Chrome Your Default Browser TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips Acronis Online Backup DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows iFixit Offers Gadget Repair Manuals Online Vista style sidebar for Windows 7 Create Nice Charts With These Web Based Tools Track Daily Goals With 42Goals Video Toolbox is a Superb Online Video Editor Fun with 47 charts and graphs

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• Data Model Dissonance

  - by Tony Davis

  So often at the start of the development of database applications, there is a premature rush to the keyboard. Unless, before we get there, we’ve mapped out and agreed the three data models, the Conceptual, the Logical and the Physical, then the inevitable refactoring will dog development work. It pays to get the data models sorted out up-front, however ‘agile’ you profess to be. The hardest model to get right, the most misunderstood, and the one most neglected by the various modeling tools, is the conceptual data model, and yet it is critical to all that follows. The conceptual model distils what the business understands about itself, and the way it operates. It represents the business rules that govern the required data, its constraints and its properties. The conceptual model uses the terminology of the business and defines the most important entities and their inter-relationships. Don’t assume that the organization’s understanding of these business rules is consistent or accurate. Too often, one department has a subtly different understanding of what an entity means and what it stores, from another. If our conceptual data model fails to resolve such inconsistencies, it will reduce data quality. If we don’t collect and measure the raw data in a consistent way across the whole business, how can we hope to perform meaningful aggregation? The conceptual data model has more to do with business than technology, and as such, developers often regard it as a worthy but rather arcane ceremony like saluting the flag or only eating fish on Friday. However, the consequences of getting it wrong have a direct and painful impact on many aspects of the project. If you adopt a silo-based (a.k.a. Domain driven) approach to development), you are still likely to suffer by starting with an incomplete knowledge of the domain. Even when you have surmounted these problems so that the data entities accurately reflect the business domain that the application represents, there are likely to be dire consequences from abandoning the goal of a shared, enterprise-wide understanding of the business. In reading this, you may recall experiences of the consequence of getting the conceptual data model wrong. I believe that Phil Factor, for example, witnessed the abandonment of a multi-million dollar banking project due to an inadequate conceptual analysis of how the bank defined a ‘customer’. We’d love to hear of any examples you know of development projects poleaxed by errors in the conceptual data model. Cheers, Tony

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• Achieving decoupling in Model classes

  - by Guven

  I am trying to test-drive (or at least write unit tests) my Model classes but I noticed that my classes end up being too coupled. Since I can't break this coupling, writing unit tests is becoming harder and harder. To be more specific: Model Classes: These are the classes that hold the data in my application. They resemble pretty much the POJO (plain old Java objects), but they also have some methods. The application is not too big so I have around 15 model classes. Coupling: Just to give an example, think of a simple case of Order Header - Order Item. The header knows the item and the item knows the header (needs some information from the header for performing certain operations). Then, let's say there is the relationship between Order Item - Item Report. The item report needs the item as well. At this point, imagine writing tests for Item Report; you need have a Order Header to carry out the tests. This is a simple case with 3 classes; things get more complicated with more classes. I can come up with decoupled classes when I design algorithms, persistence layers, UI interactions, etc... but with model classes, I can't think of a way to separate them. They currently sit as one big chunk of classes that depend on each other. Here are some workarounds that I can think of: Data Generators: I have a package that generates sample data for my model classes. For example, the OrderHeaderGenerator class creates OrderHeaders with some basic data in it. I use the OrderHeaderGenerator from my ItemReport unit-tests so that I get an instance to OrderHeader class. The problem is these generators get complicated pretty fast and then I also need to test these generators; defeating the purpose a little bit. Interfaces instead of dependencies: I can come up with interfaces to get rid of the hard dependencies. For example, the OrderItem class would depend on the IOrderHeader interface. So, in my unit tests, I can easily mock the behaviour of an OrderHeader with a FakeOrderHeader class that implements the IOrderHeader interface. The problem with this approach is the complexity that the Model classes would end up having. Would you have other ideas on how to break this coupling in the model classes? Or, how to make it easier to unit-test the model classes?

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• Clarification of the difference between PCI memory addressing and I/O addressing?

  - by KevinM

  Could someone please clarify the difference between memory and I/O addresses on the PCI/PCIe bus? I understand that I/O addresses are 32-bit, limited to the range 0 to 4GB, and do not map onto system memory (RAM), and that memory addresses are either 32-bit or 64-bit. I get the impression that memory addressing must map onto available RAM, is this true? That if a PCI device wishes to transfer data to a memory address, that address must exist in actual system RAM (and is allocated during PCI configuration) and not virtual memory. So if a PCI device only needs to transfer a small amount of data at a time, where there is no advantage to putting it into RAM or using DMA, then I/O addressing is fine (e.g. a parallel port implemented on a PCI card). And why do I keep reading that PCI/PCIe I/O addressing is being deprecated in favour of memory addressing? Thanks!

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