Showing entries 1 to 2
Displaying posts with tag: core dump (reset)
How to crash mysqld intentionally

While some may think I’m daft, I have a legitimate reason for wanting to crash mysqld. However first we need to find a way to crash it.

Great thanks to Alan K, Mark L, Harrison and Hartmut on #mysql-dev for several suggestions and a config option I was unaware of. My investigation even lead to a documentation bug logged as #51739.

My first thought was to find a known bug and if necessary install the correct version to test that. A good one was suggested, Bug #48508 which fails on several versions that I will use to demonstrate with, however the simplest way is to issue kill -11

By default, no core file will be produced which is what I’m seeking but with the right options this is possible. First, the user running mysqld probably has a core file limit size of 0.

$ ulimit …
[Read more]
Calculating your database size

I generally use the following MySQL INFORMATION_SCHEMA (I_S) query to Calculate Your MySQL Database Size. This query and most others that access the MySQL INFORMATION_SCHEMA can be very slow to execute because they are not real tables and are not governed by physical data, memory buffers and indexes for example but rather internal MySQL data structures.

Mark Leith indicates in his post on innodb_stats_on_metadata that Innodb performs 8 random(ish) dives in to the index, when anybody accesses any of SHOW TABLE STATUS, SHOW INDEX, INFORMATION_SCHEMA.TABLES,INFORMATION_SCHEMA.STATISTICS for InnoDB tables. This can have an effect on performance, especially with a large number of Innodb tables, and a poor ratio of innodb_buffer_pool_size to disk data+index footprint.

What is even more …

[Read more]
Showing entries 1 to 2