Problem with kernel_mutex in MySQL 5.1 and MySQL 5.5 is known: Bug report. In fact in MySQL 5.6 there are some fixes that suppose to provide a solution, but MySQL 5.6 yet has long way ahead before production, and it is also not clear if the problem is really fixed.

Meantime the problem with kernel_mutex is raising, I had three customer problems related to performance drops during the last month.

So what can be done there ? Let’s run some benchmarks.

But some theory before benchmarks. InnoDB uses kernel_mutex when it starts/stop transactions, and when InnoDB starts the transaction, usually there is loop through ALL active transactions, and this loop is inside kernel_mutex. That is to see kernel_mutex in action, we need many concurrent but short transactions.

For this we will …

Hello again!

This week I have been spending some time adding support for throttling to XtraBackup Manager as it has been considered a pre-requisite for us using the tool against our production databases.

In order to add support for throttling, the first thing I did was to look into what kind of means are available to throttle.

It seems there are two methods, both of which are mentioned in Percona's docs or blogs.

#1. Use the --throttle=N parameter. You can give this to innobackupex or to xtrabackup directly. According to the documentation this will limit xtrabackup to use N IOPs/sec when running in --backup mode.

For local machine backups this means N total read/write IOPS/sec and for incrementals this simply means N read IOPS/sec. When using streaming mode --throttle does not take effect (see #2).

#2. Use a nifty tool called "pv" (Pipe Viewer). It has a …

Over the last few years, Domas’s technique of using GDB as a profiler has become a key tool in helping us analyze MySQL when customers are having trouble. We have our own implementation of it in Percona Toolkit (pt-pmp) and we gather GDB backtraces from pt-stalk and pt-collect.

Although it’s helped us figure out a lot of problems, sometimes it doesn’t go well. Getting GDB backtraces is pretty intrusive. Here are three things that I’ve witnessed:

1. The server freezes for the duration of the process. This is the most obvious impact on the running server: GDB forklifts the process and gets a stack trace from every thread, then lets it go on working. But this can take a while. It’s usually a couple of seconds, but on big servers with a lot of memory and many threads, it can take much longer (I’ve seen tens of seconds, …

Regardless of the monitoring tool you use to monitor your databases, it can be better to monitor this tool.
No, it’s not a joke ! Do you think you can have a benefit with a monitoring tool not connected to your servers ? ( without being alerted )

I choose to talk about MONyog here but this can apply to all existing monitoring tools.
I just want to share the message, the tool does not matter, so, do it !

So, let me explain how to control if you have fresh data with MONyog.
With MONyog it’s easy because it’s an agentless monitoring tool.

There are two ways to check that :

Per server general info :

For each server, you can …

Introduction

Galera is a synchronous Multi-Master Replication for MySQL. It is therefore in competition with several other MySQL architectures:

• Master-Master Replication with MySQL
• MySQL Cluster
• The non-open source product called Schooner

Very often they can be easily replaced by Galera's synchronous Multi-Master Replication for MySQL.

All those products have some advantages and disadvantages. Very often MySQL Master-Master Replication is used in the field because of its simplicity to set-up. But after a while one faces its disadvantages which is mainly data inconsistency …

It's that time of the year where MySQL would be speakers are called to action. As usual, the main event is the MySQL spring conference, this year hosted by Percona. The call for participation to the MySQL Conference And Expo 2012 is still open until December 5th. To submit a proposal, you should register as a speaker and then fill in the form.
There is a conference committee which is already busy evaluating the proposals that have been submitted so far. The committee is demanding (I know for a fact, since I am in it!) and therefore, if you want to submit something, be very critical with yourself and polish your …

A friend of mine was building a web site so his customers could view his current inventory of transportation containers, and he asked me for help on how to sort the rows of information that appeared on his site. So, in this post, I will give you a quick example on how to sort columns on a web page.

First, let’s start with an inventory database that we will build in MySQL:

Next, here are some SQL statements to populate the MySQL database with some sample data.

In MySQL 5.6.3, that is, a while ago already, the performance schema added instrumentation for statements.

This major enhancement seem to have gone unnoticed, so a quick review of how it works, especially compared to the existing COM_ status counters that everyone is used to, can perhaps put some light here.

The MySQL server maintains 'COM_%' counters for statements executed.

These counters are available in both the session and global status.

Let's look at a few:

mysql> select variable_name from information_schema.global_status
where variable_name like "com\_%" order by variable_name limit 20;
+------------------------+
| variable_name          |
+------------------------+
| COM_ADMIN_COMMANDS     |
| COM_ALTER_DB           |
| COM_ALTER_DB_UPGRADE   |
| COM_ALTER_EVENT        |
| COM_ALTER_FUNCTION     |
| COM_ALTER_PROCEDURE    |
| COM_ALTER_SERVER       |
| …

I like this blog ,because I learn some knowledge from it.Thank you very much.

sure, no problem