Are there good free CDNs on the Web

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Are there some good free CDNs on the Web? There are some free CDNs in the Web. Cloudflare: https://www.cloudflare.com CloudFlare protects and accelerates any website online. Once your website is a part of the CloudFlare community, its web traffic is routed through our intelligent global network. We automatically optimize the delivery of your web pages
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QEMU/KVM Network Mechanisms

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Introduction As we know, network subsystems are important in computer systems since they are I/O systems and need to be optimized with many algorithms and skills. This article will introduce how QEMU/KVM [2] network part works. In order to put everything simple and easy to understand, we will begin with several examples and then understand
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I/O Microscopy: Tasks’ Disk I/O Information with High Accuracy

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Abstract Most popular task monitor systems (such as top, iotop, proc, etc) can only get tasks’ disk I/O information like tasks’ I/O utilization percentage every seconds due to kernel timer/tick frequency and high time cost of system interfaces. This article presents I/O Microscopy, a new way to get tasks’ disk I/O information with high accuracy.
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Make Better Decisions for Your Businesses with Data Visualization

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In today’s time, data visualization has become a significant part of the success story of an organization. With the help of right techniques, visualizing data can reveal insights which the management staff can use in their decision-making in order to make sound data-driven decisions. Mapping software is among the robust data visualization tools that you
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x-data-plane feature in QEMU/KVM

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Abstract In systems, sometimes, we use one global lock to keep synchronization among different threads. This principle also happens in QEMU/KVM (http://wiki.qemu.org/Main_Page) system. However, this may cause lock contention problem. The performance/scalability of whole system will be decreased. In order to solve this problem in QEMU/KVM, x-data-plane feature is designed/implemented, which the high-level idea is
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How migration thread works inside of Linux Kernel

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Abstract In computer systems, resources have to be balanced so that the performance will be better based on the same hardware. In Linux Kernel system, we will see some migration kernel threads running as daemons to do this kind of jobs as follows. In this article, we will discuss how Linux Kernel balances its hardware/software
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Which Checksum Tool on Linux is Faster?

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It is common practice to calculate the checksums for files to check its integrity. For large files, the checksum computation is slow. Now I am wondering why it is so slow and whether choosing another tool will be better. In this post, I try three common tools md5sum, sha1sum and crc32 to compute checksums on
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What Is the Name of the Linux-based OS: A Survey

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You may already well know “Linux” and may also use the “operating system based on the Linux kernel” directly or indirectly (you are indirectly using it now as this site is hosted on Linux). But how should we name the OS based on Linux? You may know there is GNU/Linux naming controversy. Different people have
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SSD Enabled For DreamHost Shared Hosting: Simple Performance Measurement

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SSD is common for VPS and PaaS virtual machines for higher I/O performance. Now, it is coming to shared hosting too. DreamHost states that “Now with solid state drives (SSDs), our standard web hosting loads pages 200% faster”. We ourselves are happy to know this performance improvement with the price kept the same. Good work,
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Making GPT Partition Table and Creating Partitions Using parted in Linux

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My best favorite disk partition table manipulation tools are cfdisk/fdisk on Linux. However, for large disks, cfdisk/fdisk (of the versions by this post is written) will just give up with a message suggesting GPT partition table format and using GNU parted like WARNING: The size of this disk is 6.0 TB (6001042391040 bytes). DOS partition
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How to Create Fedora 20 Domain-U on Fedora 20 Domain-0

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In this post, creating a file-backed virtual block device (VBD) and installing Fedora 20 in the Xen DomU via internet will be introduced. This domain is created on a Fedora 20 Dom0 as introduced in https://www.systutorials.com/installing-xen-on-fedora-20-as-domain-0/. For better performance, you may consider using LVM backed VM. Create file-backed VBD The actual space of VBD will
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How to Install, Run and Uninstall VMware Player and VirtualBox on Fedora Linux

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VMware Player and VirtualBox are two cool and free full virtualization solutions and both can run on top of a Linux host. In this post, I introduce how to install, run, and uninstall VMware Player and VirtualBox on Fedora Linux. VMware Player Install VMware Player Download the installation bundle from VMware’s website. For example, the
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Improving ssh/scp Performance by Choosing Suitable Ciphers

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Update on Oct. 9, 2014: You should be aware of the possible security problems of blowfish and it is suggested not to be used. Instead, you may consider ChaCha20 as suggested by Tony Arcieri. To use this with OpenSSH, you need to specify the Ciphers in your .ssh/config files as chacha20-poly1305@openssh.com possibly with another default
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Accelerating WordPress with WP Super Cache, Opcache and Autoptimize

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WordPress can be very fast after some effort on performance optimization with the help from its plenty of plugins. Possible ways include using cache to cut down the number of database queries, improves HTML/JavaScript/CSS code, and optimizing PHP’s performance with opcode cache. In this post, we introduce how to speed up WordPress with OPcache, page
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Making Emacs Start Up Faster

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I use Emacs in terminals and start/close Emacs frequently as needed like in a file checking-editing-closing loop. However, Emacs seems take some time to start up especially some heavy modes are used. How to make Emacs start up faster? (If you just want the solution/script first, find the command in the summary section.) My solution
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Big Data Benchmark from AMPLab of UC Berkeley

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Benchmarks are important to understand the performance and quantitative and qualitative comparison of different systems. Many analytic frameworks, such as Hive, Impala and Shark, are designed and implemented these years and become fundamental software for processing big data. How to benchmark these big data analytic systems is an interesting problem. The Big Data Benchmark The
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SSH Port Forwarding on Linux

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Port forwarding (or tunnelling) is a method to forward one network traffic to another. We will introduce how to forward ports using SSH tunnel in this post. A simple example Let’s start with a simple and useful example: we want to forward local port 8080 to server:port. We can easily do this by using ssh
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Managing Xen Dom0′s CPU and Memory

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The performance of Xen’s Dom0 is important for the overall system. The disk and network drivers are running on Dom0. I/O intensive guests’ workloads may consume lots Dom0′s CPU cycles. The Linux kernel calculates various network related parameters based on the amount of memory at boot time. The kernel also allocate memory for storing memory
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How to Measure Time Accurately in Programs

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It is quite common to measure the time in programs using APIs like clock() and gettimeofday(). We may also want to measure the time “accurately” for certain purposes, such as measuring a small piece of code’s execution time for performance analysis, or measuring the time in time-sensitive game software. It is hard to measure the
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Favorite Sayings by John Ousterhout – Precious Experience and Advice for Building Systems

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John Ousterhout is a professor of Deparment of Computer Science from Stanford University. One recent project he is working on is the RAMCloud, a “new class of storage, based entirely in DRAM, that is 2-3 orders of magnitude faster than existing storage systems”. He posts his “Favorite Sayings” on his homepage. These sayings are precious
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