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Displaying posts with tag: Linux (reset)

Why buffered writes are sometimes stalled
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 Many people think buffered write (write()/pwrite()) is fast because it does not do disk access. But this is not always true. Buffered write sometimes does disk access by itself, or waits for some disk accesses by other threads. Here are three common cases where write() takes longer time (== causing stalls).

1. Read Modify Write

Suppose the following logic. Opening aaa.dat without O_DIRECT/O_SYNC, writing 1000 bytes sequentially for 100,000 times, then flushing by fsync().

fd=open("aaa.dat", O_WRONLY);
for(i=0; i< 100000; i++) {
write(fd, buf, 1000);
}
fsync(fd);
 You might think each write() will finish fast enough (at least less than 0.1ms) because it shouldn't do any disk access. But it is not always true.
 Operating System manages I/O by page. It's 4KB








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Open Source Enigma Project
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The wild and crazy guys over at S&T Geotronics, James Sanderson and Marc Tessier, have decided to go full tilt with a Kickstarter version of their DIY Open Enigma Project.  For those who missed the fanfare last year, they were featured on Instructables showing how to build an Arduino-based encryption machine that works exactly like a WWII era Enigma.  You know, the thing that

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Sandboxed MySQL Utilities – HowTo
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Often I would need to work on customer servers where MySQL Utilities would be a really good fit for the tools I need. However, I would not want to mess around with the customer servers just to have it running so I would have the tools built and sandboxed on its own directory where I can cleanup later. Here’s how:

cd ~
wget http://mysql.mirrors.hoobly.com/Downloads/MySQLGUITools/mysql-utilities-1.4.1.tar.gz
tar xzf mysql-utilities-1.4.1.tar.gz
cd mysql-utilities-1.4.1
python setup.py build
python setup.py install --root=/home/revin/mysql-utilities-1.4.1
export PYTHONPATH=.:/home/revin/mysql-utilities-1.4.1/usr/lib/python2.6/site-packages
/home/revin/mysql-utilities-1.4.1/usr/bin/mysqlfrm --help

Your source of the package and install directory may vary – enjoy!

Mac Mini to the rescue
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In teaching, I had a problem because my students have different base operating systems, like Windows 7, Windows 8, Linux, and Mac OS X. I needed a teaching and lecture platform that would let me teach it all (not to mention support their environments). That meant it had to virtualize any of the following with a portable device:

  • Windows 7 or 8 hosting natively an Oracle Database 11g XE, 11g, or 12c and MySQL Database 5.6
  • Windows 7 or 8 hosting a Fedora or Oracle Unbreakable Linux VM (3 or 4 GB) with Oracle Database 11g XE, 11g, or 12c and MySQL Database 5.6
  • Mac OS X hosting a Fedora or Oracle Unbreakable Linux VM (3 or 4 GB) with Oracle Database 11g XE,
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and now for something completely different…
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As many of you know, I’ve been working in the MySQL (http://www.mysql.com) world for quite a while now. IN fact, it was nearly 10 years ago when I first started hacking on MySQL Cluster (https://www.mysql.com/products/cluster/) at MySQL AB.

Most recently, I was at Percona which was a wonderful journey where over my nearly three years there the company at least doubled in size, launched several new software products and greatly improved the quality and frequency of releases.

However the time has come for something

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Correcting mysql.sock connection error
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I write this post over to have a quick access to this tutorial than to promote the blog. The problem For Several times this has happened to me, always install a new server, or personal machine. I install mysql ,… Continue Reading →

Continue reading Correcting mysql.sock connection error

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  • Open a port on Fedora
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    Since MySQL Workbench 6.0 isn’t available for Fedora, Version 20, I’m having my students install it on their local Windows and Mac OS X operating systems. You can configure the /etc/sysconfig/iptables file to enable port 3306 after installing MySQL on Fedora.

    You can open a port by adding the following line to the /etc/sysconfig/iptables file (Fedora’s instructions on editing iptables). The file won’t exist initially, but you can create it by running the following command as the root superuser or sudoer:

    shell> service iptables save

    You you can run the following commands as the root superuser, which

      [Read more...]
    2013 in review: The year of the Linux distro
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    When looking back at 2013, one of the things that really stand out is what we’ve done with MySQL in Linux distros. At least it stands out to me, but for most people it’s probably the janitorial work that they never notice as long as everything keeps working perfectly. Although invisible to most, this is the important work that makes it possible for all Linux users to run MySQL.

    Most distros are maintained by volunteers doing packaging work in their spare time, and we as software developers should be very grateful for all the work and effort they put into distributing our software (for free!). I know we at Oracle are!

    We’ve had a distro-like project of our own in 2013. We have created our own repositories for various Linux distros (I hope to see more in the future), so that users

      [Read more...]
    Steven Sinofsky on Disruption
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    There is a good article over at Re-Code by ex-Microsoft VP Steven Sinofsky called "The Four Stages of Disruption".  It describes the evolution of products and markets through disruption, drawing from Sinofsky's own insights and also building on the work of Everett Rogers ("The Diffusion of Innovations") and Clayton Christensen ("

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    on swapping and kernels
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    There is much more to write about all the work we do at Facebook with memory management efficiency on our systems, but there was this one detour investigation in the middle of 2012 that I had to revisit recently courtesy of Wikipedia.

    There are lots of factors that make machines page out memory segments into disk, thus slowing everything down and locking software up – from file system cache pressure to runaway memory leaks to kernel drivers being greedy. But certain swap-out scenarios are confusing – systems seem to have lots of memory available, with proper settings file system cache should not cause swapping, and obviously in production environment all the memory leaks are ironed out.

    And yet in mid-2012 we noticed that our new kernel machines were swapping out for no obvious reason. When it comes to swapping, MySQL community will always point to Jeremy’s post on

      [Read more...]
    10 Newer Entries Showing entries 31 to 40 of 1137 10 Older Entries

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