Don't assume,assume makes an ass of you and me.

发布网友发布时间：2022-05-04 11:09

共5个回答

懂视网时间：2022-05-08 00:39

MySQL has a number of global buffers, i.e. your SGA. There are also a number of per session/thread buffers that combined with other memory usage constitutes an unbounded PGA. One of the most common errors in mis-configured MySQL environments is the setting of the 4 primary per session buffers thinking they are global buffers.

Global buffers include:

key_buffer_size – For MyISAM Indexes (note you can define multiple key_buffer’s The MyISAM Key Cache)

innodb_buffer_pool_size – For Innodb Table/Indexs

innodb_additional_mem_pool_size – Innodb additional data dictionary data

query_cache_size – The MySQL Query Cache

The four important per session buffers are:

read_buffer_size

read_rnd_buffer_size

sort_buffer_size

join_buffer_size

I have seen people see these values > 5M. The defaults range from 128K to 256K. My advice for any values above 256K is simple. What proof do you have this works better? When nothing is forthcoming, the first move is to revert to defaults or a maximum of 256K for some benchmarkable results. The primary reason for this is MySQL internally as quoted by Monty Taylor – for values > 256K, it uses mmap() instead of malloc() for memory allocation.

These are not all the per session buffers you need to be aware of. Others include thread_stack, max_allowed_packet,binlog_cache_size and most importantly max_connections.

MySQL also uses memory in other areas most noticeably in internal temporary tables and MEMORY based tables.

As I mentioned, there is no bound for the total process memory allocation for MySQL, so some incorrectly configured variables can easily blow your memory usage.

References

Read Buffer performance hit by Monty Taylor

参考：

http://ronaldbradford.com/blog/dont-assume-per-session-buffers-2010-03-08/

热心网友时间：2022-05-07 21:47

不要老是设想，设想让你和我都变成了蠢驴。
不过后面的assume应该是名词形式assumption才对

热心网友时间：2022-05-07 23:05

Don't assume,assume makes an ass of you and me.
不要想当然，那只会让你我失去方向。

assume 假定, 设想, 采取, 呈现
make an ass of 愚弄,欺骗

热心网友时间：2022-05-08 00:39

不要猜忌，猜忌使你和我都变得愚蠢。

热心网友时间：2022-05-08 02:31

不要设想，设想使你我变傻。

Don&#39;t assume,assume makes an ass of you and me.

References

Don't assume,assume makes an ass of you and me.