This variable controls how often disc_copies tables are dumped from memory.
The default value is 4, which means if the size of the log is greater than
the size of table / 4, then a dump occurs. To make table dumps happen more
often, increase the value. I've found setting this to 40 works well for my
purposes.

默认每执行100次write ,才会dump 到硬盘一次,
调大这个值,即增大dump的间隔,即，如果你write很频繁，可以试着调大此值，
同时也需要更大的内存支持
This variable defines the maximum number of writes to the transaction log
before a new dump is performed. The default value is 100, so a new
transaction log dump is performed after every 100 writes. If you're doing
hundreds or thousands of writes in a short period of time, then there's no
way mnesia can keep up. I set this value to 50000, which is a huge
increase, but I have enough RAM to handle it. If you're worried that this
high value means the transaction log will rarely get dumped when there's
very few writes occuring, there's also a dump_log_time_threshold
configuration variable, which by default dumps the log every 3 minutes.

跟dump_log_write_threshold配合的一个参数，
每3min执行一次dump操作,主要是当write数据很不频繁，达不到
dump_log_write_threshold的值，到了时间仍然进行dump操作，

连续多次收到这样一条消息的原因，这里有说明
http://erlang.2086793.n4.nabble.com/my-mnesia-is-lazy-td2114608.html
you start mnesia and then you put your laptop to sleeep or do nothing.

you come back the next day, open your laptop and you find mnesia
complains about being overloaded.

It basically is because you didn't do any transactions for a day.

It has nothing to do with being overloaded and mnesia should
differentiate this case.