From: Andrei Maxim <andrei@...>
Date: 2008-04-16T23:38:34+09:00
Subject: Re: ruby memory allocation

On 16.04.2008, at 16:50, M. Edward (Ed) Borasky wrote:
> Emanuele Ricci wrote:
>> I just discovered that ruby allocates memory in 8Mb chunks.
>> Forgive my ignorance.
>> Is there a way to change this behaviour? Since my app runs in an
>> environment with very strict memory constraints, a memory spike of  
>> 8Mb
>> can be lethal...
>> I would change it to a lower figure.
>> It doesn't matter if I have to patch my ruby source files in order to
>> achieve this goal.
>> Any clues?
>> Thank you in advance,
>> Emanuele Ricci.
>
> That may not be Ruby's fault entirely. In many cases, the size of  
> memory chunks delivered by "malloc" and its friends is determined by  
> the compiler or operating system. I've worked on systems where you  
> got the next higher power of two, for example. If you asked for  
> 5,000 you got 8192, if you asked for 65 you got 128, etc. And many  
> modern systems won't give you less than a physical page.
>
> A physical page on most x86 operating systems is 4096 bytes, so 8 MB  
> is 2048 pages. There is also an option to run larger pages in Linux.  
> What OS and architecture are you on?

 From _why's article "The Fully Upturned Bin" [1] I see that by  
default Ruby allocates a minimum of 8 MB for the object heap. Isn't  
this related to the OP's question?

[1]: http://whytheluckystiff.net/articles/theFullyUpturnedBin.html