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  • Can I share a TV card?

    - by Boris
    My environment: 2 PCs, a desktop and a laptop, both on Oneiric they are connected together by ethernet wire nfs-common is installed and configured: the desktop is the server a TV tuner card is installed on the desktop, I can watch TV with the software Me-TV It works fine, TV on desktop, and my network too: I share folders thanks to NFS. But I would like more: How can I share my TV tuner card from the desktop and be able to watch TV on the laptop too? If possible I would like a solution that allows me to keep using the software Me-TV, on both PCs. I bet that there is a solution to create a fake TV card on the 2nd PC with xNBD. I'm trying xnbd-server --target /dev/dvb/adapter0/demux0 but I cant make it work. Trying to understand some examples of xNBD command lines, it seems to be meant only for sharing disk player. If someone as ever used xNBD, he's welcome.

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  • after new install 12.04 black screen with blinking cursor

    - by gregor
    I installed 12.04 and I got after boot black screen.Next I started in filesafe mode but filesafeX (all options)do not work(black screen.Then I started root shell , remounted rw HD and on prompt built xorg.conf with: $X -configure I have edited xorg.conf to delete obsolete monitors and screens. After reboot I get black screen with blinking cursor (no terminals) what can I do? how to edit xorg.conf when this could be a problem?## Heading ## hardware:radeon hd5470 and i3 with i915

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  • How to Share Files Online with Ubuntu One

    - by Chris Hoffman
    Ubuntu One, Ubuntu’s built-in cloud file storage service, allows you to make files publically available online or share them privately with others. You can share files over the Internet right from Ubuntu’s file browser. Ubuntu One has two file-sharing methods: Publish, which makes a file publically available on the web to anyone who knows its address, and Share, which shares a folder with other Ubuntu One users. HTG Explains: What Is Two-Factor Authentication and Should I Be Using It? HTG Explains: What Is Windows RT and What Does It Mean To Me? HTG Explains: How Windows 8′s Secure Boot Feature Works & What It Means for Linux

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  • U Central Florida Streamlines Administrative Apps

    - by jay.richey
    The University of Central Florida is wrapping up a multi-year implementation of new enterprise applications that includes a combination of Oracle software and Sun hardware to streamline its administrative processes and help manage student growth. The Orlando-based university currently has more than 56,000 students, making it the second largest American university by enrollment, behind only Arizona State University, which has more than 70,400 students. Read more...

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  • ODI 12c - Loading Files into Oracle, community post from ToadWorld

    - by David Allan
    There's a complete soup to nuts post from Deepak Vohra on the Oracle community pages of ToadWorld on loading a fixed length file into the Oracle database. This post is interesting from a few fronts; firstly this is the out of the box experience, no specialized KMs so just basic integration from getting the software installed to running a mapping. Also it demonstrates fixed length file integration including how to use the ODI UI to define the fields and pertinent properties.  Check the blog post out below.... http://www.toadworld.com/platforms/oracle/w/wiki/10935.loading-text-file-data-into-oracle-database-12c-with-oracle-data-integrator-12c.aspx Hopefully you also find this useful, many thanks to Deepak for sharing his experiences. You could take this example further and illustrate how to load into Oracle using the LKM File to Oracle via External table knowledge module which will perform much better and also leverage such things as using wildcards for loading many files into the 12c database.

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  • Mobile Linux Gets Support From Chip Vendors

    <b>Hardware Central:</b> "The development of Linux on mobile devices may be poised to get a boost thanks to the formation of a new industry group called Linaro, backed by a consortium of chip vendors including ARM, Freescale, Texas Instruments, Samsung and ST-Ericsson."

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  • SQL SERVER – Core Concepts – Elasticity, Scalability and ACID Properties – Exploring NuoDB an Elastically Scalable Database System

    - by pinaldave
    I have been recently exploring Elasticity and Scalability attributes of databases. You can see that in my earlier blog posts about NuoDB where I wanted to look at Elasticity and Scalability concepts. The concepts are very interesting, and intriguing as well. I have discussed these concepts with my friend Joyti M and together we have come up with this interesting read. The goal of this article is to answer following simple questions What is Elasticity? What is Scalability? How ACID properties vary from NOSQL Concepts? What are the prevailing problems in the current database system architectures? Why is NuoDB  an innovative and welcome change in database paradigm? Elasticity This word’s original form is used in many different ways and honestly it does do a decent job in holding things together over the years as a person grows and contracts. Within the tech world, and specifically related to software systems (database, application servers), it has come to mean a few things - allow stretching of resources without reaching the breaking point (on demand). What are resources in this context? Resources are the usual suspects – RAM/CPU/IO/Bandwidth in the form of a container (a process or bunch of processes combined as modules). When it is about increasing resources the simplest idea which comes to mind is the addition of another container. Another container means adding a brand new physical node. When it is about adding a new node there are two questions which comes to mind. 1) Can we add another node to our software system? 2) If yes, does adding new node cause downtime for the system? Let us assume we have added new node, let us see what the new needs of the system are when a new node is added. Balancing incoming requests to multiple nodes Synchronization of a shared state across multiple nodes Identification of “downstate” and resolution action to bring it to “upstate” Well, adding a new node has its advantages as well. Here are few of the positive points Throughput can increase nearly horizontally across the node throughout the system Response times of application will increase as in-between layer interactions will be improved Now, Let us put the above concepts in the perspective of a Database. When we mention the term “running out of resources” or “application is bound to resources” the resources can be CPU, Memory or Bandwidth. The regular approach to “gain scalability” in the database is to look around for bottlenecks and increase the bottlenecked resource. When we have memory as a bottleneck we look at the data buffers, locks, query plans or indexes. After a point even this is not enough as there needs to be an efficient way of managing such large workload on a “single machine” across memory and CPU bound (right kind of scheduling)  workload. We next move on to either read/write separation of the workload or functionality-based sharing so that we still have control of the individual. But this requires lots of planning and change in client systems in terms of knowing where to go/update/read and for reporting applications to “aggregate the data” in an intelligent way. What we ideally need is an intelligent layer which allows us to do these things without us getting into managing, monitoring and distributing the workload. Scalability In the context of database/applications, scalability means three main things Ability to handle normal loads without pressure E.g. X users at the Y utilization of resources (CPU, Memory, Bandwidth) on the Z kind of hardware (4 processor, 32 GB machine with 15000 RPM SATA drives and 1 GHz Network switch) with T throughput Ability to scale up to expected peak load which is greater than normal load with acceptable response times Ability to provide acceptable response times across the system E.g. Response time in S milliseconds (or agreed upon unit of measure) – 90% of the time The Issue – Need of Scale In normal cases one can plan for the load testing to test out normal, peak, and stress scenarios to ensure specific hardware meets the needs. With help from Hardware and Software partners and best practices, bottlenecks can be identified and requisite resources added to the system. Unfortunately this vertical scale is expensive and difficult to achieve and most of the operational people need the ability to scale horizontally. This helps in getting better throughput as there are physical limits in terms of adding resources (Memory, CPU, Bandwidth and Storage) indefinitely. Today we have different options to achieve scalability: Read & Write Separation The idea here is to do actual writes to one store and configure slaves receiving the latest data with acceptable delays. Slaves can be used for balancing out reads. We can also explore functional separation or sharing as well. We can separate data operations by a specific identifier (e.g. region, year, month) and consolidate it for reporting purposes. For functional separation the major disadvantage is when schema changes or workload pattern changes. As the requirement grows one still needs to deal with scale need in manual ways by providing an abstraction in the middle tier code. Using NOSQL solutions The idea is to flatten out the structures in general to keep all values which are retrieved together at the same store and provide flexible schema. The issue with the stores is that they are compromising on mostly consistency (no ACID guarantees) and one has to use NON-SQL dialect to work with the store. The other major issue is about education with NOSQL solutions. Would one really want to make these compromises on the ability to connect and retrieve in simple SQL manner and learn other skill sets? Or for that matter give up on ACID guarantee and start dealing with consistency issues? Hybrid Deployment – Mac, Linux, Cloud, and Windows One of the challenges today that we see across On-premise vs Cloud infrastructure is a difference in abilities. Take for example SQL Azure – it is wonderful in its concepts of throttling (as it is shared deployment) of resources and ability to scale using federation. However, the same abilities are not available on premise. This is not a mistake, mind you – but a compromise of the sweet spot of workloads, customer requirements and operational SLAs which can be supported by the team. In today’s world it is imperative that databases are available across operating systems – which are a commodity and used by developers of all hues. An Ideal Database Ability List A system which allows a linear scale of the system (increase in throughput with reasonable response time) with the addition of resources A system which does not compromise on the ACID guarantees and require developers to learn new paradigms A system which does not force fit a new way interacting with database by learning Non-SQL dialect A system which does not force fit its mechanisms for providing availability across its various modules. Well NuoDB is the first database which has all of the above abilities and much more. In future articles I will cover my hands-on experience with it. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: NuoDB

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  • PASS 13 Dispatches: moving to the cloud

    - by Tony Davis
    PASS Summit 13, Day 1 keynote by Quentin Clarke and we're hearing about “redefiniing mission critical in the cloud”. With a move to the Windows Azure cloud comes the promise of capacity on demand, automatic HA, backups, patching and so on, as well as passing responsibility to MS for managing hardware, upgrades and so on. However, for many databases and applications the best route to the cloud is not necessarily obvious. For most, the path of least resistance is IaaS – SQL Server in a Azure VM. It removes the hardware burden but you still have to manage your databases and implementing HA for SQL Server is your responsibility. Also, scaling up comes at quite a cost – the biggest VM (8 CPU cores, 56 GB RAM, 16 1TB drives with 500 IOPS each) weighs in at over over $4500 per month. With PaaS, in the form of Windows SQL Database, you get a “3-copies replica set” so HA comes out-of the box, and removes the majority of the administration burden, but you are moving your database into a very different environment. For a start, it's a shared environment, with other customers using the same compute nodes in the cluster, and potentially even sharing the same database (multi-tenancy). Unless you pay for SQL DB Premium edition, the resources available for your workload will depends on how nicely others “play” in the shared environment. You'll potentially need to do a lot of tuning, and application rewriting to avoid throttling issues, optimising application-database communication to deal with increased latency between the two, and so on. You'll need aggressive application caching. You'll also need retry logic and to deal with (expected) node failure and the need to reconnect. In Tuesday's PASS Summit pre-con from the SQLCAT team, they spent a lot of time covering some of the telemetric techniques (collect into Azure storage the necessary monitoring data) to perform capacity planning, work out the hotspots and bottlenecks in your cloud applications. Tools like WAD (Windows Azure Diagnostics), performance counters SQL Database DMVs, and others, will be essential. Of course, to truly exploit the vast horizontal scaling that is available from the existence of thousands of compute nodes, you'll also need to need to consider how to “shard” your data so Azure can move it between nodes at will. Finding the right path to the Cloud isn't easy, but it's coming. I spoke to people one year ago who saw no real benefit in trying to move their infrastructure and databases to the cloud, but now at their company, it's the conversation that won't go away. Tony.  

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  • Has Little Endian won?

    - by espertus
    When teaching recently about the Big vs. Little Endian battle, a student asked whether it had been settled, and I realized I didn't know. Looking at the Wikipedia article, it seems that the most popular current OS/architecture pairs use Little Endian but that Internet Protocol specifies Big Endian for transferring numeric values in packet headers. Would that be a good summary of the current status? Do current network cards or CPUs provide hardware support for switching byte order?

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  • How can I make Ubuntu One work on windows? It says "File Sync starting..." forever

    - by morph
    I'm using Ubuntu One 2.0.1 on Windows 7 64-bit, and I want to sync my files but the application refuses to. It says "File Sync starting" forever. I left it from morning to evening and it's still the same. Also, I tried reinstalling and deleting registry files then installing again but this didn't help. Im sharing my Pictures, Music and Documents folders. In Ubuntu, sync is working ok. I searched Google and found many people having same problem without a solution.

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  • Speaking at the Great Indian Developer Summit this week

    This week I will be speaking at the Great Indian Developer Summit in Bangalore, India for the second year in a row. My sessions are: GIDS.Net (Tuesday) Data Warehousing Made Easy What's New in SQL Server 2008 R2 (PowerPivot is shown here as well!) Sharing Business Logic between Silverlight and .NET GIDS.Web (Wednesday) Building Line of Business Applications with Silverlight 4.0 (RIA Services) GIDS.Seminar (Friday) Agile Tools and Teams In addition to my talks, Telerik will also staff a booth and have demos of all of our products and some tee shirts to give away. I will also be at the booth all day to answer your questions on my talks. See you at GIDS! Technorati Tags: Telerik,Agile,Silverlight,PowerPivot Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Amazon SOA: database as a Service

    - by Martin Lee
    There is an interesting interview with Werner Vogels which is partly about how Amazon does Service Oriented Architecture: For us service orientation means encapsulating the data with the business logic that operates on the data, with the only access through a published service interface. No direct database access is allowed from outside the service, and there’s no data sharing among the services. I do not understand that. Why do they need to 'wrap' a database into some layer if it already can be consumed as a service by other service through database adaptors? Does Amazon do that just because they need to expose the database to third parties or because of anything else? Why "no direct database access is allowed"? What are the advantages of such an architectural decision?

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  • SQL Server Capacity Planner

    - by Colt
    Apart from the capacity planner tool for System Center and SharePoint Server, I was looking for a tool which can help me to estimate the capacity of SQL Server. I found an article on Microsoft.com for SQL Server 2000 sizing but unfortunately the links are obseleted and dead: Dell PowerMatch Server Sizing Software Compaq Active Answer Resources Finally I found an article that is "close" to my interest: Hardware and Software Requirements for Installing SQL Server 2008 If any of you heard of any tools in capacity planning or sizing for SQL Server, please drop me a message. Thanks,Colt

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  • Solution For Printer Problems

    The Most Common Fixes For Printer Problems A Printer is a hardware device that gives an impression in a text or graphic format. In general, the printer is not part of your computer system; you have ... [Author: Kaisar Adnan - Computers and Internet - April 12, 2010]

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  • How to fix v4l2 Input/output error, vostro 1510 ubuntu 13.04 64bits?

    - by Fabio C. Barrionuevo da Luz
    I clean install upgrade to ubuntu 13.04 64btis, but the cheese and simplecv are no longer functioning properly. In previous versions of Ubuntu, everything worked normally. By running the two programs, I get the following message: libv4l2: error turning on stream: Input/output error ps: sorry, my English is very ugly. full hardware description of my notebook on this link: https://gist.github.com/luzfcb/5873728

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  • PTLQueue : a scalable bounded-capacity MPMC queue

    - by Dave
    Title: Fast concurrent MPMC queue -- I've used the following concurrent queue algorithm enough that it warrants a blog entry. I'll sketch out the design of a fast and scalable multiple-producer multiple-consumer (MPSC) concurrent queue called PTLQueue. The queue has bounded capacity and is implemented via a circular array. Bounded capacity can be a useful property if there's a mismatch between producer rates and consumer rates where an unbounded queue might otherwise result in excessive memory consumption by virtue of the container nodes that -- in some queue implementations -- are used to hold values. A bounded-capacity queue can provide flow control between components. Beware, however, that bounded collections can also result in resource deadlock if abused. The put() and take() operators are partial and wait for the collection to become non-full or non-empty, respectively. Put() and take() do not allocate memory, and are not vulnerable to the ABA pathologies. The PTLQueue algorithm can be implemented equally well in C/C++ and Java. Partial operators are often more convenient than total methods. In many use cases if the preconditions aren't met, there's nothing else useful the thread can do, so it may as well wait via a partial method. An exception is in the case of work-stealing queues where a thief might scan a set of queues from which it could potentially steal. Total methods return ASAP with a success-failure indication. (It's tempting to describe a queue or API as blocking or non-blocking instead of partial or total, but non-blocking is already an overloaded concurrency term. Perhaps waiting/non-waiting or patient/impatient might be better terms). It's also trivial to construct partial operators by busy-waiting via total operators, but such constructs may be less efficient than an operator explicitly and intentionally designed to wait. A PTLQueue instance contains an array of slots, where each slot has volatile Turn and MailBox fields. The array has power-of-two length allowing mod/div operations to be replaced by masking. We assume sensible padding and alignment to reduce the impact of false sharing. (On x86 I recommend 128-byte alignment and padding because of the adjacent-sector prefetch facility). Each queue also has PutCursor and TakeCursor cursor variables, each of which should be sequestered as the sole occupant of a cache line or sector. You can opt to use 64-bit integers if concerned about wrap-around aliasing in the cursor variables. Put(null) is considered illegal, but the caller or implementation can easily check for and convert null to a distinguished non-null proxy value if null happens to be a value you'd like to pass. Take() will accordingly convert the proxy value back to null. An advantage of PTLQueue is that you can use atomic fetch-and-increment for the partial methods. We initialize each slot at index I with (Turn=I, MailBox=null). Both cursors are initially 0. All shared variables are considered "volatile" and atomics such as CAS and AtomicFetchAndIncrement are presumed to have bidirectional fence semantics. Finally T is the templated type. I've sketched out a total tryTake() method below that allows the caller to poll the queue. tryPut() has an analogous construction. Zebra stripping : alternating row colors for nice-looking code listings. See also google code "prettify" : https://code.google.com/p/google-code-prettify/ Prettify is a javascript module that yields the HTML/CSS/JS equivalent of pretty-print. -- pre:nth-child(odd) { background-color:#ff0000; } pre:nth-child(even) { background-color:#0000ff; } border-left: 11px solid #ccc; margin: 1.7em 0 1.7em 0.3em; background-color:#BFB; font-size:12px; line-height:65%; " // PTLQueue : Put(v) : // producer : partial method - waits as necessary assert v != null assert Mask = 1 && (Mask & (Mask+1)) == 0 // Document invariants // doorway step // Obtain a sequence number -- ticket // As a practical concern the ticket value is temporally unique // The ticket also identifies and selects a slot auto tkt = AtomicFetchIncrement (&PutCursor, 1) slot * s = &Slots[tkt & Mask] // waiting phase : // wait for slot's generation to match the tkt value assigned to this put() invocation. // The "generation" is implicitly encoded as the upper bits in the cursor // above those used to specify the index : tkt div (Mask+1) // The generation serves as an epoch number to identify a cohort of threads // accessing disjoint slots while s-Turn != tkt : Pause assert s-MailBox == null s-MailBox = v // deposit and pass message Take() : // consumer : partial method - waits as necessary auto tkt = AtomicFetchIncrement (&TakeCursor,1) slot * s = &Slots[tkt & Mask] // 2-stage waiting : // First wait for turn for our generation // Acquire exclusive "take" access to slot's MailBox field // Then wait for the slot to become occupied while s-Turn != tkt : Pause // Concurrency in this section of code is now reduced to just 1 producer thread // vs 1 consumer thread. // For a given queue and slot, there will be most one Take() operation running // in this section. // Consumer waits for producer to arrive and make slot non-empty // Extract message; clear mailbox; advance Turn indicator // We have an obvious happens-before relation : // Put(m) happens-before corresponding Take() that returns that same "m" for T v = s-MailBox if v != null : s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 // unlock slot to admit next producer and consumer return v Pause tryTake() : // total method - returns ASAP with failure indication for auto tkt = TakeCursor slot * s = &Slots[tkt & Mask] if s-Turn != tkt : return null T v = s-MailBox // presumptive return value if v == null : return null // ratify tkt and v values and commit by advancing cursor if CAS (&TakeCursor, tkt, tkt+1) != tkt : continue s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 return v The basic idea derives from the Partitioned Ticket Lock "PTL" (US20120240126-A1) and the MultiLane Concurrent Bag (US8689237). The latter is essentially a circular ring-buffer where the elements themselves are queues or concurrent collections. You can think of the PTLQueue as a partitioned ticket lock "PTL" augmented to pass values from lock to unlock via the slots. Alternatively, you could conceptualize of PTLQueue as a degenerate MultiLane bag where each slot or "lane" consists of a simple single-word MailBox instead of a general queue. Each lane in PTLQueue also has a private Turn field which acts like the Turn (Grant) variables found in PTL. Turn enforces strict FIFO ordering and restricts concurrency on the slot mailbox field to at most one simultaneous put() and take() operation. PTL uses a single "ticket" variable and per-slot Turn (grant) fields while MultiLane has distinct PutCursor and TakeCursor cursors and abstract per-slot sub-queues. Both PTL and MultiLane advance their cursor and ticket variables with atomic fetch-and-increment. PTLQueue borrows from both PTL and MultiLane and has distinct put and take cursors and per-slot Turn fields. Instead of a per-slot queues, PTLQueue uses a simple single-word MailBox field. PutCursor and TakeCursor act like a pair of ticket locks, conferring "put" and "take" access to a given slot. PutCursor, for instance, assigns an incoming put() request to a slot and serves as a PTL "Ticket" to acquire "put" permission to that slot's MailBox field. To better explain the operation of PTLQueue we deconstruct the operation of put() and take() as follows. Put() first increments PutCursor obtaining a new unique ticket. That ticket value also identifies a slot. Put() next waits for that slot's Turn field to match that ticket value. This is tantamount to using a PTL to acquire "put" permission on the slot's MailBox field. Finally, having obtained exclusive "put" permission on the slot, put() stores the message value into the slot's MailBox. Take() similarly advances TakeCursor, identifying a slot, and then acquires and secures "take" permission on a slot by waiting for Turn. Take() then waits for the slot's MailBox to become non-empty, extracts the message, and clears MailBox. Finally, take() advances the slot's Turn field, which releases both "put" and "take" access to the slot's MailBox. Note the asymmetry : put() acquires "put" access to the slot, but take() releases that lock. At any given time, for a given slot in a PTLQueue, at most one thread has "put" access and at most one thread has "take" access. This restricts concurrency from general MPMC to 1-vs-1. We have 2 ticket locks -- one for put() and one for take() -- each with its own "ticket" variable in the form of the corresponding cursor, but they share a single "Grant" egress variable in the form of the slot's Turn variable. Advancing the PutCursor, for instance, serves two purposes. First, we obtain a unique ticket which identifies a slot. Second, incrementing the cursor is the doorway protocol step to acquire the per-slot mutual exclusion "put" lock. The cursors and operations to increment those cursors serve double-duty : slot-selection and ticket assignment for locking the slot's MailBox field. At any given time a slot MailBox field can be in one of the following states: empty with no pending operations -- neutral state; empty with one or more waiting take() operations pending -- deficit; occupied with no pending operations; occupied with one or more waiting put() operations -- surplus; empty with a pending put() or pending put() and take() operations -- transitional; or occupied with a pending take() or pending put() and take() operations -- transitional. The partial put() and take() operators can be implemented with an atomic fetch-and-increment operation, which may confer a performance advantage over a CAS-based loop. In addition we have independent PutCursor and TakeCursor cursors. Critically, a put() operation modifies PutCursor but does not access the TakeCursor and a take() operation modifies the TakeCursor cursor but does not access the PutCursor. This acts to reduce coherence traffic relative to some other queue designs. It's worth noting that slow threads or obstruction in one slot (or "lane") does not impede or obstruct operations in other slots -- this gives us some degree of obstruction isolation. PTLQueue is not lock-free, however. The implementation above is expressed with polite busy-waiting (Pause) but it's trivial to implement per-slot parking and unparking to deschedule waiting threads. It's also easy to convert the queue to a more general deque by replacing the PutCursor and TakeCursor cursors with Left/Front and Right/Back cursors that can move either direction. Specifically, to push and pop from the "left" side of the deque we would decrement and increment the Left cursor, respectively, and to push and pop from the "right" side of the deque we would increment and decrement the Right cursor, respectively. We used a variation of PTLQueue for message passing in our recent OPODIS 2013 paper. ul { list-style:none; padding-left:0; padding:0; margin:0; margin-left:0; } ul#myTagID { padding: 0px; margin: 0px; list-style:none; margin-left:0;} -- -- There's quite a bit of related literature in this area. I'll call out a few relevant references: Wilson's NYU Courant Institute UltraComputer dissertation from 1988 is classic and the canonical starting point : Operating System Data Structures for Shared-Memory MIMD Machines with Fetch-and-Add. Regarding provenance and priority, I think PTLQueue or queues effectively equivalent to PTLQueue have been independently rediscovered a number of times. See CB-Queue and BNPBV, below, for instance. But Wilson's dissertation anticipates the basic idea and seems to predate all the others. Gottlieb et al : Basic Techniques for the Efficient Coordination of Very Large Numbers of Cooperating Sequential Processors Orozco et al : CB-Queue in Toward high-throughput algorithms on many-core architectures which appeared in TACO 2012. Meneghin et al : BNPVB family in Performance evaluation of inter-thread communication mechanisms on multicore/multithreaded architecture Dmitry Vyukov : bounded MPMC queue (highly recommended) Alex Otenko : US8607249 (highly related). John Mellor-Crummey : Concurrent queues: Practical fetch-and-phi algorithms. Technical Report 229, Department of Computer Science, University of Rochester Thomasson : FIFO Distributed Bakery Algorithm (very similar to PTLQueue). Scott and Scherer : Dual Data Structures I'll propose an optimization left as an exercise for the reader. Say we wanted to reduce memory usage by eliminating inter-slot padding. Such padding is usually "dark" memory and otherwise unused and wasted. But eliminating the padding leaves us at risk of increased false sharing. Furthermore lets say it was usually the case that the PutCursor and TakeCursor were numerically close to each other. (That's true in some use cases). We might still reduce false sharing by incrementing the cursors by some value other than 1 that is not trivially small and is coprime with the number of slots. Alternatively, we might increment the cursor by one and mask as usual, resulting in a logical index. We then use that logical index value to index into a permutation table, yielding an effective index for use in the slot array. The permutation table would be constructed so that nearby logical indices would map to more distant effective indices. (Open question: what should that permutation look like? Possibly some perversion of a Gray code or De Bruijn sequence might be suitable). As an aside, say we need to busy-wait for some condition as follows : "while C == 0 : Pause". Lets say that C is usually non-zero, so we typically don't wait. But when C happens to be 0 we'll have to spin for some period, possibly brief. We can arrange for the code to be more machine-friendly with respect to the branch predictors by transforming the loop into : "if C == 0 : for { Pause; if C != 0 : break; }". Critically, we want to restructure the loop so there's one branch that controls entry and another that controls loop exit. A concern is that your compiler or JIT might be clever enough to transform this back to "while C == 0 : Pause". You can sometimes avoid this by inserting a call to a some type of very cheap "opaque" method that the compiler can't elide or reorder. On Solaris, for instance, you could use :"if C == 0 : { gethrtime(); for { Pause; if C != 0 : break; }}". It's worth noting the obvious duality between locks and queues. If you have strict FIFO lock implementation with local spinning and succession by direct handoff such as MCS or CLH,then you can usually transform that lock into a queue. Hidden commentary and annotations - invisible : * And of course there's a well-known duality between queues and locks, but I'll leave that topic for another blog post. * Compare and contrast : PTLQ vs PTL and MultiLane * Equivalent : Turn; seq; sequence; pos; position; ticket * Put = Lock; Deposit Take = identify and reserve slot; wait; extract & clear; unlock * conceptualize : Distinct PutLock and TakeLock implemented as ticket lock or PTL Distinct arrival cursors but share per-slot "Turn" variable provides exclusive role-based access to slot's mailbox field put() acquires exclusive access to a slot for purposes of "deposit" assigns slot round-robin and then acquires deposit access rights/perms to that slot take() acquires exclusive access to slot for purposes of "withdrawal" assigns slot round-robin and then acquires withdrawal access rights/perms to that slot At any given time, only one thread can have withdrawal access to a slot at any given time, only one thread can have deposit access to a slot Permissible for T1 to have deposit access and T2 to simultaneously have withdrawal access * round-robin for the purposes of; role-based; access mode; access role mailslot; mailbox; allocate/assign/identify slot rights; permission; license; access permission; * PTL/Ticket hybrid Asymmetric usage ; owner oblivious lock-unlock pairing K-exclusion add Grant cursor pass message m from lock to unlock via Slots[] array Cursor performs 2 functions : + PTL ticket + Assigns request to slot in round-robin fashion Deconstruct protocol : explication put() : allocate slot in round-robin fashion acquire PTL for "put" access store message into slot associated with PTL index take() : Acquire PTL for "take" access // doorway step seq = fetchAdd (&Grant, 1) s = &Slots[seq & Mask] // waiting phase while s-Turn != seq : pause Extract : wait for s-mailbox to be full v = s-mailbox s-mailbox = null Release PTL for both "put" and "take" access s-Turn = seq + Mask + 1 * Slot round-robin assignment and lock "doorway" protocol leverage the same cursor and FetchAdd operation on that cursor FetchAdd (&Cursor,1) + round-robin slot assignment and dispersal + PTL/ticket lock "doorway" step waiting phase is via "Turn" field in slot * PTLQueue uses 2 cursors -- put and take. Acquire "put" access to slot via PTL-like lock Acquire "take" access to slot via PTL-like lock 2 locks : put and take -- at most one thread can access slot's mailbox Both locks use same "turn" field Like multilane : 2 cursors : put and take slot is simple 1-capacity mailbox instead of queue Borrow per-slot turn/grant from PTL Provides strict FIFO Lock slot : put-vs-put take-vs-take at most one put accesses slot at any one time at most one put accesses take at any one time reduction to 1-vs-1 instead of N-vs-M concurrency Per slot locks for put/take Release put/take by advancing turn * is instrumental in ... * P-V Semaphore vs lock vs K-exclusion * See also : FastQueues-excerpt.java dice-etc/queue-mpmc-bounded-blocking-circular-xadd/ * PTLQueue is the same as PTLQB - identical * Expedient return; ASAP; prompt; immediately * Lamport's Bakery algorithm : doorway step then waiting phase Threads arriving at doorway obtain a unique ticket number Threads enter in ticket order * In the terminology of Reed and Kanodia a ticket lock corresponds to the busy-wait implementation of a semaphore using an eventcount and a sequencer It can also be thought of as an optimization of Lamport's bakery lock was designed for fault-tolerance rather than performance Instead of spinning on the release counter, processors using a bakery lock repeatedly examine the tickets of their peers --

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  • DHCP server with multiple interfaces on ubuntu, destroys default gateway

    - by Henrik Alstad
    I use Ubuntu, and I have many interfaces. eth0, which is my internet connection, and it gets its info from a DHCP-server totally outisde of my control. I then have eth1,eth2,eth3 and eth4 which I have created a DHCP-server for.(ISC DHCP-Server) It seems to work, and I even get an IP-address from the foreign DHCP-server on the internet facing interface. However, for some reason it seems my gateway for eth0 became screwed after I installed my local DHCP-server for eth1-eth4. (I think so because I got an IP for eth0, and I can ping other stuff on the local network, but I cannot get access to the internet). My eth0-specific info in /etc/network/interfaces: auto lo iface lo inet loopback auto eth0 iface eth0 inet dhcp auto eth1 iface eth1 inet static address 10.0.1.1 netmask 255.255.255.0 network 10.0.1.0 broadcast 10.0.1.255 gateway 10.0.1.1 mtu 8192 auto eth2 iface eth2 inet static address 10.0.2.1 netmask 255.255.255.0 network 10.0.2.0 broadcast 10.0.2.255 gateway 10.0.2.1 mtu 8192 My /etc/default/isc-dhcp-server: INTERFACES="eth1 eth2 eth3 eth4" So why does my local DHCP-server fuck up the gateway for eth0, when I tell it not to listen to eth0? Anyone see the problem or what I can do to fix it? The problem seems indeed to be the gateways. "netstat -nr" gives: 0.0.0.0 --- 10.X.X.X ---- 0.0.0.0 --- UG 0 0 0 eth3 It should have been 0.0.0.0 129.2XX.X.X 0.0.0.0 UG 0 0 0 eth0 So for some reason, my local DHCP-server overrides the gateway I get from the network DHCP. Edit: dhcp.conf looks like this(I included info only for eth1 subnet): ddns-update-style none; not authoritative; subnet 10.0.1.0 netmask 255.255.255.0 { interface eth1; option domain-name "example.org"; option domain-name-servers ns1.example.org, ns2.example.org; default-lease-time 600; max-lease-time 7200; range 10.0.1.10 10.0.1.100; host camera1_1 { hardware ethernet 00:30:53:11:24:6E; fixed-address 10.0.1.10; } host camera2_1 { hardware ethernet 00:30:53:10:16:70; fixed-address 10.0.1.11; } } Also, it seems that the gateway is correctly set if I run "/etc/init.d/networking restart" in a terminal, but that's not helpful for me, I need the correct gateway to be set during startup, and i'd rather find the source of the problem

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  • Where can I buy freely redistributable (creative commons) game assets?

    - by Erlend
    I'd like to know about any 3D asset shops out there that specialize in game assets and, most importantly, license their assets under an open license like Creative Commons or similarly permissive. We are looking to buy some professional looking assets for use and redistribution with our open source 3D game engine. The problem is that all the commercial 3D assets we've come by are only sold under very restrictive licenses, which won't allow us to include the models in our code repository (since free code hosting repositories require that all your data, including media, is open source or otherwise copyleft) nor in turn redistribute the assets as part of our downloadable SDK. I realize this sounds like a weak business idea, since users could just buy the asset and start sharing it with everyone. But somehow this has worked for hundreds of WordPress theme shops, so I was hoping maybe someone's trying similar things for commercial game assets.

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  • Atlanta Laptop Repair

    Is your laptop running slow or crashing? To the average person laptop problems can be confusing. You do not know whether it';s hardware or a software issue that is causing the problem. An experienced ... [Author: Steven Yaniz - Computers and Internet - March 30, 2010]

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  • Video White Paper: Mega-Project Management: Reducing Risk & Complexity across the Value Chain

    - by Melissa Centurio Lopes
    Watch this short video white paper, to learn how Oracle Primavera can help you keep projects on track and protect your investments. You can also download the full white paper “Mega-Project Management: Reducing Risk & Complexity Across the Value Chain” to gain more in depth information about strategies for collaborating and sharing information and data in a systematic way across the value chain. Download the white paper in order to learn how your company can get the expected payoff from your next mega project. Register now to download the full complementary white paper, and discover how to: Improve decision-making and accountability through enterprise-wide visibility, workflows, and collaboration Reduce financial and performance risk

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  • ACE a Session at Oracle OpenWorld

    - by Oracle OpenWorld Blog Team
    By Bob Rhubart Oracle ACE Sessions at Oracle OpenWorldAs you're finalizing your Oracle OpenWorld travel plans and taking advantage of Schedule Builder to plan your week in San Francisco, make sure you add some Oracle ACE sessions to your schedule."What's an Oracle ACE?" you ask. Members of the Oracle ACE Program are the most active members of the Oracle community, frequently sharing their substantial insights and real-world expertise with Oracle technologies through articles, blogs, social networks, and as presenters at Oracle OpenWorld and other events.With so many great sessions at this year's event, building your schedule can involve making a lot of tough choices. But you'll find that the sessions led by Oracle ACEs will be the icing on the cake of your Oracle OpenWorld content experience.To see a full list of Oracle ACE sessions at Oracle OpenWorld and other Oracle conferences that same week, check out this blog post that lists them all.

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  • Can Microsoft Build Appliances?

    - by andrewbrust
    Billy Hollis, my Visual Studio Live! colleague and fellow Microsoft Regional Director said recently, and I am paraphrasing, that the computing world, especially on the consumer side, has shifted from one of building hardware and software that makes things possible to do, to building products and technologies that make things easy to do.  Billy crystalized things perfectly, as he often does. In this new world of “easy to do,” Apple has done very well and Microsoft has struggled.  In the old world, customers wanted a Swiss Army Knife, with the most gimmicks and gadgets possible.  In the new world, people want elegantly cutlery.  They may want cake cutters and utility knives too, but they don’t want one device that works for all three tasks.  People don’t want tools, they want utensils.  People don’t want machines.  They want appliances. Microsoft Appliances: They Do Exist Microsoft has built a few appliance-like devices.  I would say XBox 360 is an appliance,  It’s versatile, mind you, but it’s the kind of thing you plug in, turn on and use, as opposed to set-up, tune, and open up to upgrade the internals.  Windows Phone 7 is an appliance too.  It’s a true smartphone, unlike Windows Mobile which was a handheld computer with a radio stack.  Zune is an appliance too, and a nice one.  It hasn’t attained much traction in the market, but that’s probably because the seminal consumer computing appliance -- the iPod – got there so much more quickly. In the embedded world, Mediaroom, Microsoft’s set-top product for the cable industry (used by AT&T U-Verse and others) is an appliance.  So is Microsoft’s Sync technology, used in Ford automobiles.  Even on the enterprise side, Microsoft has an appliance: SQL Server Parallel Data Warehouse Edition (PDW) combines Microsoft software with select OEMs’ server, networking and storage hardware.  You buy the appliance units from the OEMs, plug them in, connect them and go. I would even say that Bing is an appliance.  Not in the hardware sense, mind you.  But from the software perspective, it’s a single-purpose product that you visit or run, use and then move on.  You don’t have to install it (except the iOS and Android native apps where it’s pretty straightforward), you don’t have to customize it, you don’t have to program it.  Basically, you just use it. Microsoft Appliances that Should Exist But Microsoft builds a bunch of things that are not appliances.  Media Center is not an appliance, and it most certainly should be.  Instead, it’s an app that runs on Windows 7.  It runs full-screen and you can use this configuration to conceal the fact that Windows is under it, but eventually something will cause you to abandon that masquerade (like Patch Tuesday). The next version of Windows Home Server won’t, in my opinion, be an appliance either.  Now that the Drive Extender technology is gone, and users can’t just add and remove drives into and from a single storage pool, the product is much more like a IT server and less like an appliance-premised one.  Much has been written about this decision by Microsoft.  I’ll just sum it up in one word: pity. Microsoft doesn’t have anything remotely appliance-like in the tablet category, either.  Until it does, it likely won’t have much market share in that space either.  And of course, the bulk of Microsoft’s product catalog on the business side is geared to enterprise machines and not personal appliances. Appliance DNA: They Gotta Have It. The consumerization of IT is real, because businesspeople are consumers too.  They appreciate the fit and finish of appliances at home, and they increasingly feel entitled to have it at work too.  Secure and reliable push email in a smartphone is necessary, but it isn’t enough.  People want great apps and a pleasurable user experience too.  The full Microsoft Office product is needed at work, but a PC with a keyboard and mouse, or maybe a touch screen that uses a stylus (or requires really small fingers), to run Office isn’t enough either.  People want a flawless touch experience available for the times they want to read and take quick notes.  Until Microsoft realizes this fully and internalizes it, it will suffer defeats in the consumer market and even setbacks in the business market.  Think about how slow the Office upgrade cycle is…now imagine if the next version of Office had a first-class alternate touch UI and consider the possible acceleration in adoption rates. Can Microsoft make the appliance switch?  Can the appliance mentality become pervasive at the company?  Can Microsoft hasten its release cycles dramatically and shed the “some assembly required” paradigm upon which many of its products are based?  Let’s face it, the chances that Microsoft won’t make this transition are significant. But there are also encouraging signs, and they should not be ignored.  The appliances we have already discussed, especially Xbox, Zune and Windows Phone 7, are the most obvious in this regard.  The fact that SQL Server has an appliance SKU now is a more subtle but perhaps also more significant outcome, because that product sits so smack in the middle of Microsoft’s enterprise stack.  Bing is encouraging too, especially given its integrated travel, maps and augmented reality capabilities.  As Bing gains market share, Microsoft has tangible proof that it can transform and win, even when everyone outside the company, and many within it, would bet otherwise. That Great Big Appliance in the Sky Perhaps the most promising (and evolving) proof points toward the appliance mentality, though, are Microsoft’s cloud offerings -- Azure and BPOS/Office 365.  While the cloud does not represent a physical appliance (quite the opposite in fact) its ability to make acquisition, deployment and use of technology simple for the user is absolutely an embodiment of the appliance mentality and spirit.  Azure is primarily a platform as a service offering; it doesn’t just provide infrastructure.  SQL Azure does likewise for databases.  And Office 365 does likewise for SharePoint, Exchange and Lync. You don’t administer, tune and manage servers; instead, you create databases or site collections or mailboxes and start using them. Upgrades come automatically, and it seems like releases will come more frequently.  Fault tolerance and content distribution is just there.  No muss.  No fuss.  You use these services; you don’t have to set them up and think about them.  That’s how appliances work.  To me, these signs point out that Microsoft has the full capability of transforming itself.  But there’s a lot of work ahead.  Microsoft may say they’re “all in” on the cloud, but the majority of the company is still oriented around its old products and models.  There needs to be a wholesale cultural transformation in Redmond.  It can happen, but product management, program management, the field and executive ranks must unify in the effort. So must partners, and even customers.  New leaders must rise up and Microsoft must be able to see itself as a winner.  If Microsoft does this, it could lock-in decades of new success, and be a standard business school case study for doing so.  If not, the company will have missed an opportunity, and may see its undoing.

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  • Ubuntu server spontaneous reboot

    - by user1941407
    I have got two ubuntu 12.04 servers(xeon e3). Sometimes(several days) each server spontaneously reboots. HDDs and other hardware are ok. Which logfile can help find a reason of the problem? UPDATED. hardware: xeon e3 processor, intel server motherboard, 32gb ddr3 ecc, mdadm mirror hdd raid for system, mdadm ssd raid for database(postgres). Both servers have similar (not identical) components. Smart is OK. It seems that the problem is in the software. Python process and database are running on this servers. Syslog (time of reboot): Aug 23 13:42:23 xeon hddtemp[1411]: /dev/sdc: WDC WD15NPVT-00Z2TT0: 34 C Aug 23 13:42:23 xeon hddtemp[1411]: /dev/sdd: WDC WD15NPVT-00Z2TT0: 34 C Aug 23 13:43:24 xeon hddtemp[1411]: /dev/sdc: WDC WD15NPVT-00Z2TT0: 34 C Aug 23 13:43:24 xeon hddtemp[1411]: /dev/sdd: WDC WD15NPVT-00Z2TT0: 34 C Aug 23 13:44:14 xeon sensord: Chip: acpitz-virtual-0 Aug 23 13:44:14 xeon sensord: Adapter: Virtual device Aug 23 13:44:14 xeon sensord: temp1: 27.8 C Aug 23 13:44:14 xeon sensord: temp2: 29.8 C Aug 23 13:44:14 xeon sensord: Chip: coretemp-isa-0000 Aug 23 13:44:14 xeon sensord: Adapter: ISA adapter Aug 23 13:44:14 xeon sensord: Physical id 0: 37.0 C Aug 23 13:44:14 xeon sensord: Core 0: 37.0 C Aug 23 13:44:14 xeon sensord: Core 1: 37.0 C Aug 23 13:44:14 xeon sensord: Core 2: 37.0 C Aug 23 13:44:14 xeon sensord: Core 3: 37.0 C Aug 23 13:44:24 xeon hddtemp[1411]: /dev/sdc: WDC WD15NPVT-00Z2TT0: 34 C Aug 23 13:44:24 xeon hddtemp[1411]: /dev/sdd: WDC WD15NPVT-00Z2TT0: 34 C Aug 23 13:47:01 xeon kernel: imklog 5.8.6, log source = /proc/kmsg started. Aug 23 13:47:01 xeon rsyslogd: [origin software="rsyslogd" swVersion="5.8.6" x-pid="582" x-info="http://www.rsyslog.com"] start Aug 23 13:47:01 xeon rsyslogd: rsyslogd's groupid changed to 103 Aug 23 13:47:01 xeon rsyslogd: rsyslogd's userid changed to 101 Aug 23 13:47:00 xeon rsyslogd-2039: Could not open output pipe '/dev/xconsole' [try http://www.rsyslog.com/e/2039 ] Aug 23 13:47:01 xeon kernel: [ 0.000000] Initializing cgroup subsys cpuset Aug 23 13:47:01 xeon kernel: [ 0.000000] Initializing cgroup subsys cpu Aug 23 13:47:01 xeon kernel: [ 0.000000] Initializing cgroup subsys cpuacct Aug 23 13:47:01 xeon kernel: [ 0.000000] Linux version 3.11.0-26-generic (buildd@komainu) (gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) ) #45~precise1-Ubuntu SMP Tue Jul 15 04:02:35 UTC 2014 (Ubuntu 3.11.0-26.45~precise1-generic 3.11.10.12) Aug 23 13:47:01 xeon kernel: [ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-3.11.0-26-generic root=UUID=0daa7f53-6c74-47d2-873e-ebd339cd39b0 ro splash quiet vt.handoff=7 Aug 23 13:47:01 xeon kernel: [ 0.000000] KERNEL supported cpus: Aug 23 13:47:01 xeon kernel: [ 0.000000] Intel GenuineIntel Aug 23 13:47:01 xeon kernel: [ 0.000000] AMD AuthenticAMD Aug 23 13:47:01 xeon kernel: [ 0.000000] Centaur CentaurHauls Aug 23 13:47:01 xeon kernel: [ 0.000000] e820: BIOS-provided physical RAM map: Aug 23 13:47:01 xeon kernel: [ 0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009bbff] usable Aug 23 13:47:01 xeon kernel: [ 0.000000] BIOS-e820: [mem 0x000000000009bc00-0x000000000009ffff] reserved Dmseg - nothing strange.

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