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Displaying posts with tag: Programming (reset)
Wake up European DBA, call for papers for Percona Live London 2014 is open!

Call for papers for Percona Live London 2014 is open. For the fourth consecutive year, PLUK is going to be one of the best community event in Europe.
I have the honour of being conference committee chairman and the hard task to reviewing the talks with my colleagues of the committee.

First, let me introduce the committee members:

  • Art van Scheppingen (Spil Games)
  • Nicolai Plum (Booking.com)
  • Luis Motta Campos (Ebay Classifieds Group)
  • Colin Charles (MariaDB)
  • David Busby (Percona)
  • Morgan Tocker (Oracle)
  • Cédric PEINTRE (Dailymotion)

Amazing, isn’t it?! I think we couldn’t have a better committee for a community event.
I’m very glad to take part in the adventure with you guys!

And if you wonder what the committee does, …

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GUUG Frühjahrsfachgespräch 2014: CfP ends on May 31st!

The German Unix User Group (GUUG) will hold their annual conference "Frühjahrsfachgespräch" on September 23-26 this year (I know, not really "Frühjahr" anymore, but this is how it is).

The Call for Presentations is still open until May 31st. Talks can be proposed in German and English, and there are slots for longer tutorials as well.

The range of possible topics is broad, so if you think you have anything interesting to share with a very passionate and technical audience of sysadmins and developers, here are some suggestions:

  • Operating Systems/Applications: architectures, privilege concepts, new developments, administration, mobile systems
  • Relevant new OS Kernel features: new developments in Linux-, BSD- or other Spen …
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Arduino to the max: 11x11x11 LED-cube

March 29 2014 is Arduino day, also in Labitat. This is a good opportunity to describe my LED-cube:

 

This LED-cube pulls a number of tricks to get the most out of just a single normal Arduino Uno. A meager 16 MHz and 2048 bytes of RAM goes a long way with sufficient ingenuity and creativity. Here are some highlights:

  • 12-bit PWM, 16 grayscales non-linear.
  • Animations generated on-board, read from SD-card, or streamed over USB.
  • 178 Hz refresh rate, transferring 3 Mbits/s of data to the LED driver shift registers.
  • 50 Hz animation framerate, receiving 269kbit/s of animation data over the serial port.
  • Approximately half of spare CPU time available for on-board generation of …
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Using MASTER_GTID_WAIT() to avoid stale reads from slaves in replication

I have just implemented MASTER_GTID_WAIT() in MariaDB 10.0. This can be used to give a very elegant solution to the problem of stale reads in replication read-scaleout, without incuring the overheads normally associated with synchronous replication techniques. This idea came up recently in a discussion with Stephane Varoqui, and is similar to the concept of Lamport logical clock described in this Wikipedia article.

I wanted to describe this, hoping to induce people to test and maybe start using this, as it is a simple but very neat idea, actually.

A very typical use of MariaDB/MySQL …

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Correcting mysql.sock connection error

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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More on 40% better single-threaded performance in MariaDB

In my previous post I wrote about how I achived a >40% speedup on sysbench read-only using profile-guided optimisation (PGO). While this is a preliminary result, I though it was so interesting that it deserved early mention. The fact that any benchmark can be improved that much shows clearly that PGO is something worth looking into. Even if we will probably not improve all workloads by 40%, it seems highly likely that we can obtain significant gains also for many real workloads.

I had one or two interesting comments on the post that raise valid concerns, so I wanted to write a follow-up here, explaining some of the points in more details and going deeper into the performance counter measurements. As I wrote before, actual observations and measurements are crucial to fully understand performance of complex code on modern CPUs. Intuition and …

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40% better single-threaded performance in MariaDB

Continuing my investigation of single-threaded performance in the MariaDB server, I managed to increase throughput of single-threaded read-only sysbench by more than 40% so far:

I use read-only sysbench 0.4.12 run like this:

    sysbench --num-threads=1 --test=oltp --oltp-test-mode=simple --oltp-read-only --oltp-skip-trx run

And mysqld is run with minimal options:

    sql/mysqld --no-defaults --basedir=X --datadir=Y --innodb-buffer-pool-size=128M

With modern high-performance CPUs, it is necessary to do detailed measurements using the built-in performance counters in order to get any kind of understanding of how an application performs and what the bottlenecks are. Forget about looking at the code and counting instructions or cycles as we did in the old days. It no longer works, not even to within an order of magnitude.

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MySQL/MariaDB single-threaded performance regressions, and a lesson in thread synchronisation primit

I took a quick look at MariaDB 10.0 single-treaded performance (simple read-only sysbench). One thing immediately leaps to the eye, and I thought it worthy of mention. It contains an important lesson about the use of synchronisation primitives and in particular "atomic operations" in MariaDB (and MySQL).

I am using the Linux perf tool on this sysbench command:

  sysbench --num-threads=1 --test=oltp --oltp-test-mode=simple --oltp-read-only --oltp-skip-trx

Look at the top offender in the output from perf report:

  1,54%  mysqld  mysqld               [.] set_thread_state_v1

The only thing this does is set a string for SHOW PROCESSLIST (and the like) about what the thread is doing. And we are spending a whopping 1.5% of the total time doing this.

And why? That becomes clear when looking at the disassembly …

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Connecting your Linux to a Cisco AnyConnect (SSL) – part 3

Hi there !

 

This is the final part of using openconnect  - You can check the older ones below:

http://www.heitorlessa.com/connecting-your-linux-to-a-cisco-anyconnect-ssl-part-1/

http://www.heitorlessa.com/connecting-your-linux-to-a-cisco-anyconnect-ssl-part-2/

 

As mentioned previously, we will be covering here:

  • How to create a script to monitor such VPN using ICMP, and restart that VPN if it is down

 

I would say, this is very straight forward and does not require much knowledge, so we are going to follow the same procedure as part 2 – Show the script in parts and then a …

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Connecting your Linux to a Cisco AnyConnect (SSL) – Part 2

Hey you!

As said in the part 1 of this article, I will be covering here:

  • How to create a openconnect init script

So, concerning the init script I will be posting parts of the script first, and then will put a link for download at the end.

First of all, we need the shebang (#!/bin/bash) and then global variables that will be used along the script:

# Path variables
PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"

# VPN Variables
IFACE="sslvpn"
VPN_USER="vpn_user"
VPN_HOST="sslvpn.yourdomain.com"
VPN_PASS="vpn_password"
PID="/var/run/openconnect.pid"
TEMP_LOG="/tmp/status.txt"
INFO="Usage: $(basename "$0") (start|stop|status|restart)"

You can also define most of these options in a …

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