In vBulletin Board System there is session table contains online user information and tracking, in which forum now, what the current URL now, So it is have huge concurrent update statement, By default this table is MEMORY engine because its data not important in case MySQL restart.

I notice early loaded in MySQL and server, So I do full tuning for the server then analyze slow query using

At Days of Wonder we are huge fans of MySQL (and since about a year of the various Open Query, Percona, Google or other community patches), up to the point we’re using MySQL for about everything in production.

But since we moved to 5.0, back 3 years ago our production databases which hold our website and online game systems has a unique issue: the mysqld process uses more and more RAM, up to the point where the kernel OOM decide to kill the process.

You’d certainly think we are complete morons because we didn’t do anything in the last 3 years to fix the issue

Unfortunately, I never couldn’t …

One of the ways to import data into MySQL is using the LOAD DATA INFILE. It is a faster method than recovering from a dump, as it’s raw data instead of SQL sentences.

The import time depends on the table engine, for example, MyISAM can be 40 times faster than Innodb. Let’s benchmark this:

Preparation

I’m gonna make some benchmarking using MySQL 5.1.36 (64 bits MacOS X). I’ll need a big table, so I’ll take City from the World Database and create a huge table called “city_huge”:

CREATE TABLE city_huge LIKE CITY;

INSERT INTO city_huge 
    SELECT NULL, name, CountryCode, District, Population FROM city;
# Run this sentence 100 times,
# so city_huge table will be 100 times bigger than city.
# Tip: use a script, temporary table, stored procedure...
# or tell your monkey to do so.

SELECT COUNT(*) FROM …

This is an issue that keeps rearing its ugly head over and over again, and since it greatly affects performance, it is most important that DBAs of any DMBS running on Linux come to grips with it. So I decided to do some research and try different settings on my notebook. Here are my findings.

What can you find on the web?

A Wikipedia search for the word swappiness will come up empty (any volunteers out there want to write an article?). A Google search will show some pretty old material—the best article I found is from 2004: Linux: Tuning Swappiness. This article includes a detailed discussion with some interesting remarks by Andrew Morton, a Linux kernel maintainer.

So, what is swappiness?

Towards the end of the email thread quoted in the article, you’ll find this definition (sort of):

> I’ve read the source for where …

Why should you care about the latest “early adopter” release of the InnoDB Plugin, version 1.0.3?   One word: performance! The release introduces these features:

• Enhanced concurrency & scalability: the “Google SMP patch” using atomic instructions for mutexing
• More efficient memory allocation: ability to use more scalable platform memory allocator
• Improved out-of-the-box scalability: unlimited concurrent thread execution by default
• Dynamic tuning: at run-time, enable or disable insert buffering and adaptive hash indexing

These new performance features can yield up to twice the throughput or more, depending on your workload, platform and other tuning considerations. In another post, we explore some details about these changes, but first, what do these enhancements mean for performance and scalability?

In brief, we’ve tested …

The VM for Linux prefers system cache over application memory. What does this mean? The best way I can explain is by example.

Imagine you have 32 GB of RAM
MySQL is set to take 20 GB of RAM for a process based buffer and up to 6M for the various thread buffers.

Over a period of time the box swaps. The only thing that is running is mysql and its memory size is around 21GB for resident memory. Why does swap grow when there is plenty of memory? The reason is when a memory alloc is needed (thread based buffer is tickled) the VM will choose to use swap over allocating from the system cache, when there is not enough free memory.

DO NOT TURN OFF SWAP to prevent this. Your box will crawl, kswapd will chew up a lot of the processor, Linux needs swap enabled, lets just hope its not used.

So how do you stop Nagios pages because of swap usage? Well if you have a few choices.

…

Ever since Peter over at Percona wrote about MySQL and swap, I’ve been meaning to write this post. But after I saw Dathan Pattishall’s post on the subject, I knew I’d better actually do it.

There’s a nasty problem with Linux 2.6 even when you have a ton of RAM. No matter what you do, including setting /proc/sys/vm/swappiness = 0, your OS is going to prefer swapping stuff out rather than freeing up system cache. On a single-use machine, where the application is better at utilizing RAM than the system is, this is incredibly stupid. Our MySQL boxes are a perfect example – they run only MySQL and we want InnoDB to have a lot of RAM (32-64GB …

Hello my dear readers.

Today I have a question for all of you. What platforms (32bit or 64 bit) do you use for your servers with more than 4Gb RAM? I’m asking because recently we‘ve hit few really weird bugs in Linux kernels 2.6.18 to 2.6.22 and all those bugs were PAE-related. Now I’d really love to move all machines to 64-bit, but I’m in doubt because we don’t know too much about Rails stack (ruby, mongrel, haproxy) on 64-bit platforms (all our DB boxes are 64-bit of course).

So, please drop me a line if you have any experience (negative or positive) with Rails platform on 64-bit machines. I’d really appreciate your help.

If you have a 12-server MySQL Cluster with: 1 Management Node 3 SQL Nodes 2 Data Node Groups, 4 Data Nodes per group And each machine is configured to allocate 1G of memory for its function, how much data (data + indexes) can you store in total in your cluster? You can guess, but you get bonus points if you [...]