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  • Organization &amp; Architecture UNISA Studies &ndash; Chap 4

    - by MarkPearl
    Learning Outcomes Explain the characteristics of memory systems Describe the memory hierarchy Discuss cache memory principles Discuss issues relevant to cache design Describe the cache organization of the Pentium Computer Memory Systems There are key characteristics of memory… Location – internal or external Capacity – expressed in terms of bytes Unit of Transfer – the number of bits read out of or written into memory at a time Access Method – sequential, direct, random or associative From a users perspective the two most important characteristics of memory are… Capacity Performance – access time, memory cycle time, transfer rate The trade off for memory happens along three axis… Faster access time, greater cost per bit Greater capacity, smaller cost per bit Greater capacity, slower access time This leads to people using a tiered approach in their use of memory   As one goes down the hierarchy, the following occurs… Decreasing cost per bit Increasing capacity Increasing access time Decreasing frequency of access of the memory by the processor The use of two levels of memory to reduce average access time works in principle, but only if conditions 1 to 4 apply. A variety of technologies exist that allow us to accomplish this. Thus it is possible to organize data across the hierarchy such that the percentage of accesses to each successively lower level is substantially less than that of the level above. A portion of main memory can be used as a buffer to hold data temporarily that is to be read out to disk. This is sometimes referred to as a disk cache and improves performance in two ways… Disk writes are clustered. Instead of many small transfers of data, we have a few large transfers of data. This improves disk performance and minimizes processor involvement. Some data designed for write-out may be referenced by a program before the next dump to disk. In that case the data is retrieved rapidly from the software cache rather than slowly from disk. Cache Memory Principles Cache memory is substantially faster than main memory. A caching system works as follows.. When a processor attempts to read a word of memory, a check is made to see if this in in cache memory… If it is, the data is supplied, If it is not in the cache, a block of main memory, consisting of a fixed number of words is loaded to the cache. Because of the phenomenon of locality of references, when a block of data is fetched into the cache, it is likely that there will be future references to that same memory location or to other words in the block. Elements of Cache Design While there are a large number of cache implementations, there are a few basic design elements that serve to classify and differentiate cache architectures… Cache Addresses Cache Size Mapping Function Replacement Algorithm Write Policy Line Size Number of Caches Cache Addresses Almost all non-embedded processors support virtual memory. Virtual memory in essence allows a program to address memory from a logical point of view without needing to worry about the amount of physical memory available. When virtual addresses are used the designer may choose to place the cache between the MMU (memory management unit) and the processor or between the MMU and main memory. The disadvantage of virtual memory is that most virtual memory systems supply each application with the same virtual memory address space (each application sees virtual memory starting at memory address 0), which means the cache memory must be completely flushed with each application context switch or extra bits must be added to each line of the cache to identify which virtual address space the address refers to. Cache Size We would like the size of the cache to be small enough so that the overall average cost per bit is close to that of main memory alone and large enough so that the overall average access time is close to that of the cache alone. Also, larger caches are slightly slower than smaller ones. Mapping Function Because there are fewer cache lines than main memory blocks, an algorithm is needed for mapping main memory blocks into cache lines. The choice of mapping function dictates how the cache is organized. Three techniques can be used… Direct – simplest technique, maps each block of main memory into only one possible cache line Associative – Each main memory block to be loaded into any line of the cache Set Associative – exhibits the strengths of both the direct and associative approaches while reducing their disadvantages For detailed explanations of each approach – read the text book (page 148 – 154) Replacement Algorithm For associative and set associating mapping a replacement algorithm is needed to determine which of the existing blocks in the cache must be replaced by a new block. There are four common approaches… LRU (Least recently used) FIFO (First in first out) LFU (Least frequently used) Random selection Write Policy When a block resident in the cache is to be replaced, there are two cases to consider If no writes to that block have happened in the cache – discard it If a write has occurred, a process needs to be initiated where the changes in the cache are propagated back to the main memory. There are several approaches to achieve this including… Write Through – all writes to the cache are done to the main memory as well at the point of the change Write Back – when a block is replaced, all dirty bits are written back to main memory The problem is complicated when we have multiple caches, there are techniques to accommodate for this but I have not summarized them. Line Size When a block of data is retrieved and placed in the cache, not only the desired word but also some number of adjacent words are retrieved. As the block size increases from very small to larger sizes, the hit ratio will at first increase because of the principle of locality, which states that the data in the vicinity of a referenced word are likely to be referenced in the near future. As the block size increases, more useful data are brought into cache. The hit ratio will begin to decrease as the block becomes even bigger and the probability of using the newly fetched information becomes less than the probability of using the newly fetched information that has to be replaced. Two specific effects come into play… Larger blocks reduce the number of blocks that fit into a cache. Because each block fetch overwrites older cache contents, a small number of blocks results in data being overwritten shortly after they are fetched. As a block becomes larger, each additional word is farther from the requested word and therefore less likely to be needed in the near future. The relationship between block size and hit ratio is complex, and no set approach is judged to be the best in all circumstances.   Pentium 4 and ARM cache organizations The processor core consists of four major components: Fetch/decode unit – fetches program instruction in order from the L2 cache, decodes these into a series of micro-operations, and stores the results in the L2 instruction cache Out-of-order execution logic – Schedules execution of the micro-operations subject to data dependencies and resource availability – thus micro-operations may be scheduled for execution in a different order than they were fetched from the instruction stream. As time permits, this unit schedules speculative execution of micro-operations that may be required in the future Execution units – These units execute micro-operations, fetching the required data from the L1 data cache and temporarily storing results in registers Memory subsystem – This unit includes the L2 and L3 caches and the system bus, which is used to access main memory when the L1 and L2 caches have a cache miss and to access the system I/O resources

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  • A Small Blog About Huge Pages

    - by rickramsey
    Video Interview: What Are Linux Huge Pages?, by Ed Whalen, Oracle ACE Blog: There's Been a Change In How Huge Pages Are Allocated, by Tanel Poder, Oracle ACE Director Blog: Performance Issues with Transparent Huge Pages (thank you, Bjoern Rost!) Web: About the Car, by Smart Ridez LLC, of Woodland Hills, California - Rick Follow me on: Blog | Facebook | Twitter | Personal Twitter | YouTube | The Great Peruvian Novel

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  • Is there going to be Twinview ( or alternative) implemented for nouveau ?

    - by lisak
    as I've had heavy issues with nvidia driver regarding performance of basic X window operations (window moving, resizing, scrolling). I switched to nouveau driver. But I lost the possibility of having dual screen that I had previously thanks to nvidia twinview feature... Anyway I rather have fluent X than dual screen, but having dual screen would be nice, so I'm wondering if there is already an nouveau alternative to nvidia's twinview or if it is going to be implemented.

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  • Wait, Chrome Dev Tools could do THAT?

    Wait, Chrome Dev Tools could do THAT? Your browser is one of the most and best instrumented development platforms -- you may just not realize it yet. In this episode we'll take a whirlwind tour of how to analyze network performance, rendering and layout pipeline, as well as detecting memory leaks in your Javascript code, and using audits and extensions to build faster and better apps! From: GoogleDevelopers Views: 207 16 ratings Time: 33:40 More in Science & Technology

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  • ISV Exastack program: IBIS, Performix, Cardtek

    - by Javier Puerta
    Impact Business Information Solutions (IBIS) accelerates insights for Health Sciences decision-makers to achieve new levels productivity using Oracle’s extreme-performance system, Oracle Exadata Database Machine. Read More. Perfomix Inc Achieves Oracle Exadata Optimized Status. Read more. Cardtek Group Company SmartSoft's payment processing solution achieves Oracle Exadata Optimized status. Read more.

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  • Sybase IQ 15.4 annoncé : Sybase parie sur Hadoop et MapReduce, et défie sa maison mère ?

    Sybase IQ 15.4 annoncé pour fin novembre Sybase veut repousser les limites du Big Data avec Hadoop et MapReduce Alors que la grand messe annuelle de SAP, le SAPPHIRE NOW, battait son plein, la nouvelle filiale de l'éditeur allemand Sybase a annoncé en totale indépendance la sortie de Sybase IQ 15.4, son serveur analytique haute performance structuré en colonnes pour gérer les "big data". Alors que de son côté SAP met en avant HANA, sa nouvelle technologie de mise en cache des données (ou "In-Memory Computing") pour accélérer la vitesse de traite...

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  • Capitalize on Engineering and Information Assets throughout the Enterprise

    To facilitate information exchange, drive performance and improve corporate governance, organizations are investing in Oracle Universal Content Management to store, track and manage their digital information assets. Combined with Oracle's AutoVue visualization solutions and CADTop, Sword Group's CAD integration for UCM, engineering centric organizations can now access, view and collaborate on engineering and CAD documents throughout the enterprise for improved visibility and more informed decision making.

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  • DBA Reporting Presentation - Cambridge UG

    - by NeilHambly
    I'm now able to Report (sorry for the pun!) that my presentation on DBA Reporting I gave @ the User group on 25th November @ Red-Gate Offices in Cambridge So I have attached the Presentation in PDF format for you all to replay and view if you weren't able to attend. Here a few links you may also want to check out on some of those products we discussed Various ones like SQL NEXUS / DAIG / PAL / Internals Viewer http://www.codeplex.com/ SQL Server 2005 Performance Dashboard Reports http://www...(read more)

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  • Did Ubuntu 10.04 Achieve Its Ten Second Boot Goal?

    <b>Phoronix:</b> "Canonical expressed their plans to achieve a ten-second boot time in June of last year for Ubuntu 10.04 LTS, with their reference system being a Dell Mini 9 netbook. In February, we last checked on Ubuntu's boot performance and found it close, but not quite there yet..."

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  • Oracle OpenWorld - Events of Interest

    - by Larry Wake
    I mentioned the "Focus On Oracle Solaris" document the other day, which lists many of the Solaris-related events at Oracle OpenWorld this year; today I thought I'd highlight a few sessions you might find interesting. Monday, October 1st: 4:45 PM - Get Proactive: Best Practices for Maintaining and Upgrading Oracle Solaris (Moscone South 252) This session covers best practices for upgrading and patching and how to take advantage of unique technologies in Oracle Solaris 10 and 11. Learn how to get maximum value from My Oracle Support for both reactive and proactive requirements. Understand the benefits of secure remote access and how Oracle Support experts use collaborative shared sessions combined with Oracle Solaris technologies such as DTrace. Tuesday, October 2nd: 10:15 AM -  How to Increase Performance and Agility with an Open Data Center Fabric (Moscone South 200) If you haven't had a chance to hear about Xsigo Systems, this is a golden opportunity while you're at OpenWorld. Now part of Oracle, Xsigo's network virtualization technology is designed to increase both application performance and management efficiency, through a combination of software-defined network technology and the industry’s fastest fabric, allowing data center to converge Ethernet and Fibre Channel connectivity to a single fabric, to reduce complexity by 70 percent and CapEx by 50 percent while providing more I/O bandwidth to your applications. Wednesday, October 3rd: 10:15 AM - General Session: Oracle Solaris 11 Strategy, Engineering Insights, and Roadmap (Moscone South 103) Markus Flierl, head of Oracle Solaris Core Engineering, will outline the strategy and roadmap for Oracle Solaris,  how Oracle Solaris 11 is being deployed in cloud computing and the unique optimizations in Oracle Solaris 11 for the Oracle stack. The session also offers a sneak peek at the latest technology under development in Oracle Solaris, and what customers can expect to see in the coming updates. Plus, there are several Hands-On Labs: Monday, October 1st: 10:45 AM - 11:45 AM - Reduce Risk with Oracle Solaris Access Control to Restrain Users and Isolate Applications (Marriott Marquis - Salon 14/15) 4:45 PM - 5:45 PM - Managing Your Data with Built-In Oracle Solaris ZFS Data Services in Release 11  (Marriott Marquis - Salon 14/15) Tuesday, October 2nd: 1:15 PM - 2:15 PM - Virtualizing Your Oracle Solaris 11 Environment  (Marriott Marquis - Salon 10/11) Wednesday, October 3rd: 3:30 PM - 4:30 PM - Large-Scale Installation and Deployment of Oracle Solaris 11 (Marriott Marquis - Salon 14/15) There's plenty more--see the "Focus On Oracle Solaris" guide. See you next week in San Francisco!

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  • Oracle’s Visual CRM Solution

    Visual CRM adds the powerful visualization and document centric collaboration capabilities of Oracle’s AutoVue to Oracle’s best-in-class CRM solutions. By introducing a visual aspect to call center, field service, and ordering processes, Visual CRM helps teams provide faster responses to customer issues, optimize field service performance, and shorten ordering cycles while minimizing order errors.With Visual CRM, organizations can achieve improved customer service levels and field service operations which help drive margin, top line revenue, and customer retention.

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  • Gain Visibility

    This Industry AppsCast will discuss the importance of visibility across all projects enterprise wide and how Oracle's Primavera PPM solutions provides transparency into project status performance across all projects in your portfolio.

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  • An innovative architecture to develop business web forms (3) - Configure GridView

    This is third article in the series to introduce an innovative architecture to develop web forms in enterprise software which is high performance, productivity, configurability and maintainability than writing ASPX/MVC code directly. The article introduces how to configure gridview for search result...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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  • Does anyone do hardware benchmarks on compiling code?

    - by Colen
    I've seen a bunch of sites that benchmark new hardware on gaming performance, zipping some files, encoding a movie, or whatever. Are there any that test the impact of new hardware (like SSDs, new CPUs, RAM speeds, or whatever) on compile and link speeds, either linux or windows? It'd be really good to find out what mattered the most for compile speed and be able to focus on that, instead of just extrapolating from other benchmarks.

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  • OpenJDK default options to always use the server VM

    - by montrealmike
    I got a warning message: jvm uses the client vm, make sure to run java with the server vm for best performance by adding -server to the command line In fact, when i run java -version i get: OpenJDK Runtime Environment (IcedTea7 2.3.2) (7u7-2.3.2a-0ubuntu0.12.04.1) OpenJDK Client VM (build 23.2-b09, mixed mode, sharing) How does one go about and change OpenJDK's defaults to always start under the server VM?

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  • OBIA on Teradata - Part 4

    - by Mohan Ramanuja
    Monitoring Tools Name Action Teradata Manager (PMON) Check for down resources UNIX Check the /var/adm/streams log DBC.Software_Event_Log Check for hardware errors. Tunable ParametersFollowing parameters could be tuned for better performance Maximum Response Buffer Size (MAXRESPSIZE) Session Data Unit (SDU) Transport Date Unit (TDU) Related Links http://forums.teradata.com/forum http://www.info.teradata.com/Datawarehouse/eBrowseBy.cfm?page=TeradataDatabase http://www.teradataforum.com/ncr_pdf.htm http://www.teradata.com/blogs/ http://www.teradatamagazine.com/

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  • Introduction to Indexes

    Indexes are critical to good performance. However many people don't understand how indexes well. MVP Gail Shaw provides us with an introductory article on the basics of indexing. Join SQL Backup’s 35,000+ customers to compress and strengthen your backups "SQL Backup will be a REAL boost to any DBA lucky enough to use it." Jonathan Allen. Download a free trial now.

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  • Write and fprintf for file I/O

    - by Darryl Gove
    fprintf() does buffered I/O, where as write() does unbuffered I/O. So once the write() completes, the data is in the file, whereas, for fprintf() it may take a while for the file to get updated to reflect the output. This results in a significant performance difference - the write works at disk speed. The following is a program to test this: #include <fcntl.h #include <unistd.h #include <stdio.h #include <stdlib.h #include <errno.h #include <stdio.h #include <sys/time.h #include <sys/types.h #include <sys/stat.h static double s_time; void starttime() { s_time=1.0*gethrtime(); } void endtime(long its) { double e_time=1.0*gethrtime(); printf("Time per iteration %5.2f MB/s\n", (1.0*its)/(e_time-s_time*1.0)*1000); s_time=1.0*gethrtime(); } #define SIZE 10*1024*1024 void test_write() { starttime(); int file = open("./test.dat",O_WRONLY|O_CREAT,S_IWGRP|S_IWOTH|S_IWUSR); for (int i=0; i<SIZE; i++) { write(file,"a",1); } close(file); endtime(SIZE); } void test_fprintf() { starttime(); FILE* file = fopen("./test.dat","w"); for (int i=0; i<SIZE; i++) { fprintf(file,"a"); } fclose(file); endtime(SIZE); } void test_flush() { starttime(); FILE* file = fopen("./test.dat","w"); for (int i=0; i<SIZE; i++) { fprintf(file,"a"); fflush(file); } fclose(file); endtime(SIZE); } int main() { test_write(); test_fprintf(); test_flush(); } Compiling and running I get 0.2MB/s for write() and 6MB/s for fprintf(). A large difference. There's three tests in this example, the third test uses fprintf() and fflush(). This is equivalent to write() both in performance and in functionality. Which leads to the suggestion that fprintf() (and other buffering I/O functions) are the fastest way of writing to files, and that fflush() should be used to enforce synchronisation of the file contents.

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  • Fusion Human Capital Management - Enterprise Grade Software As a Service

    Tune into this conversation with Anand Subbaraman, Senior Director of Product Strategy for Fusion HCM and Technology, to learn how Oracle is delivering offer a complete HCM SaaS application with single-vendor accountability. Unlike other vendors, which rely on other partners to complete their solutions, Oracle Fusion HCM includes integrated modules for HR, Payroll, Benefits, Compensation, Performance, along with industry-firsts such as Workforce Predictions, Network at Work, and Talent Review - all available on the Cloud.

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  • Filing the XBRL version of Oracle's 2011 10K with the SEC using Oracle Hyperion Disclosure Management

    Oracle Hyperion Disclosure Management is designed to "demystify" the creation of XBRL documents. Featuring deep integration with existing Oracle financial reporting tools, it is the easiest and most straightforward approach to XBRL reporting for Oracle's enterprise performance management and enterprise resource planning customers. In this podcast hear how Oracle itself has improved its SEC XBRL submission process through the implementation of Oracle Hyperion Disclosure Management.

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  • Speaking About SQL Server

    - by AllenMWhite
    There's a lot of excitement in the SQL Server world right now, with the RTM (Release to Manufacturing) release of SQL Server 2012 , and the availability of SQL Server Data Tools (SSDT) . My personal speaking schedule has exploded as well. Just this past Saturday I presented a session called Gather SQL Server Performance Data with PowerShell . There are a lot of events coming up, and I hope to see you at one or more of them. Here's a list of what's scheduled so far: First, I'll be presenting a session...(read more)

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