For some reason, the history list isn't purging on one of my masters. This
is causing all kinds of weird issues/behavior with reads. Here's the last 8
or so hours of history list length:

http://i.imgur.com/Q4DEeVi.png

Here are my innodb%purge% settings.

mysql> show variables where Variable_name like 'innodb%purge%'\G
*************************** 1. row ***************************
Variable_name: innodb_max_purge_lag
Value: 1000000
*************************** 2. row ***************************
Variable_name: innodb_purge_batch_size
Value: 100
*************************** 3. row ***************************
Variable_name: innodb_purge_threads
Value: 1
3 rows in set (0.09 sec)

This machine is doing about 500-100 TPS. This manifested right after I did
an ALTER TABLE ADD COLUMN to a massive table (600mil records, 100GB of
data).

What other things can I look at to figure out how to increase bandwidth for
the purge thread?

Thanks,

*Brad Heller *| Director of Engineering | Cloudability.com | 541-231-1514 |
Skype: brad.heller | @bradhe <http://www.twitter.com/bradhe> | @cloudability
<http://www.twitter.com/cloudability>

We're hiring! https://cloudability.com/jobs
<http://www.cloudability.com/jobs>