Re: powers of two in my.cnf ? - Sasha Pachev - com.mysql.lists.mysql

4 messages in com.mysql.lists.mysqlRe: powers of two in my.cnf ?

From	Sent On	Attachments
matthew mcglynn	01 Apr 1999 21:29
Michael Widenius	02 Apr 1999 03:07
jkr...@murl.com	02 Apr 1999 08:49
Sasha Pachev	02 Apr 1999 09:17

Subject:	Re: powers of two in my.cnf ?
From:	Sasha Pachev (sas...@direct1.com)
Date:	04/02/1999 09:17:28 AM
List:	com.mysql.lists.mysql

Michael Widenius wrote:

"matthew" == matthew mcglynn <mcgl...@netjet.com> writes:

matthew> This is probably a really dumb question...

matthew> Every example of buffer settings I've seen matthew> has used powers of two. For example, from the matthew> sample configuration file: matthew> set-variable = key_buffer=16M matthew> set-variable = max_allowed_packet=1M matthew> set-variable = thread_stack=128K matthew> set-variable = max_allowed_packet=16M matthew> set-variable = keybuffer=16M

matthew> Similarly, the default table_cache is 64, and when matthew> people ask on this list about running out of file matthew> descriptors, the response is usually "set table_cache matthew> to 32".

matthew> My dumb question is: do these have to all be powers of two ?!

matthew> If for my application, a table_cache of 128 is insufficient, matthew> can I bump it to 150 or do I need to go all the way to 256 ?

Hi!

I just prefer to use powers as two as this gives you the best memory utilization with many memory allocation packages!

You don't however have to use powers of two; For the table cache 150 should be fine!

Regards, Monty

And to add to what Monty has said, powers of 2 are "holy" numbers for a programmer, just like powers of 10 are "holy" for non-programmers.