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memory

VSZ behaviour with MariaDB MEMORY tables

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We recently had the situation that a customer complained about the Oom killer terminating the MariaDB database instance from time to time. The MariaDB database configuration was sized quit OK (about 50% of RAM was used for the database) but they did not have swap configured.

MariaDB and MySQL swap analysis

# free
              total        used        free      shared  buff/cache   available
Mem:       16106332     3914228      367072      296508    11825032    11441608
Swap:      31250428      182924    31067504

# cat /proc/meminfo | grep ^Swap
SwapCached:        10056 kB
SwapTotal:      31250428 kB
SwapFree:       31067504 kB

# for file in /proc/*/status ; do
  awk '/VmSwap|Name/{
    if ( $2 != "0" )
      printf $2 " " $3
  }END{ print ""}' $file
done | grep kB | sort -k 2 -n -r

mysqld 29988 kB
plasmashell 19096 kB
kwin_x11 13444 kB
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DOAG Datenbank Konferenz 2016

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Heute war ich auf der DOAG Datenbank 2016 Konferenz in Düsseldorf. Der einzige Vortrag zum Thema MySQL war mein eigener: MySQL für Oracle DBAs. Daher hatte ich die Möglichkeit wieder mal etwas über den Zaun zu linsen. Hier meine Notizen:

MySQL Cluster analysis for foodmart

This is an automated analysis of the DBI:mysql:database=foodmart;host=localhost database for migration into MySQL Cluster. No warranty is made to the accuracy of the information.

This information should be valid for MySQL 4.1 and 5.0. Since 5.1 is not a final release yet, the numbers should be used as a guide only.

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MySQL Cluster memory sizing

MySQL Cluster is pretty fast. The reason for this is, that it is completely memory based. Nowadays memory is still, in contrary to disk, limited to your systems. Thus, before installing a MySQL Cluster you have to calculate the amount of memory you need.

To say it in advance: You should consider to only use 64-bit Linux system with huge amount (4 - 64 GB) of RAM!

In release 5.1 MySQL Cluster became disk based. Now you have the possibility to swap out some data to disk. How much it is we will probably see a little further down...

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Reading other processes memory

As you probably have experienced yet MySQL does not always provide all internal information as you might want to have them and as you are used to have from other RDBMS.

MySQL plans to improve this implementing the/a performance schema and its probably already partly done in MySQL 5.4. But who knows when this will be finished and what it contains at all...

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FromDual consulting tool collection

The following tools we use sometimes for our consulting engagements...

Caution: These tools are NOT for production use! Use with care!

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Reading other processes memory

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As you probably have experienced yet MySQL does not always provide all internal information as you might want to have them and as you are used to have from other RDBMS.

MySQL plans to improve this implementing the/a performance schema and its probably already partly done in MySQL 5.4. But who knows when this will be finished and what it contains at all...

Possible memory leak in NDB-API applications?

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A customer has recently experienced a possible memory leak in its NDB-API application. What he did was something like:

# ps aux | grep <pid>

over time and then he saw the RSS increasing. When he would have had a look a little longer he would have seen that the RSS consumption would increase up to a certain level and then becomes stable. Which is the expected behavior.

Possible Memory Leak

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