From: MenTaLguY <mental@...>
Date: 2007-10-19T05:06:18+09:00
Subject: Re: [OT] Re: Should *most* memory be release back to the system?

On Fri, 19 Oct 2007 04:13:58 +0900, Joel VanderWerf <vjoel@path.berkeley.edu> wrote:
> Yohanes Santoso wrote:
>>   mallopt(M_MMAP_THRESHOLD, 0); /* declared in malloc.h */
> 
> Very interesting. I'd like to use this as a diagnostic.
> 
> I patched ruby's main.c to call mallopt() before anything else. It seems
> to be using a huge amount of memory, though. Is this normal?

Using mmap for individual allocations means that each allocation
gets rounded up to the nearest multiple of the page size
(typically 4k).

That aside, I'm not sure it's that useful as a diagnostic; note
that only M_MMAP_MAX chunks will ever be allocated at a time with
mmap; further allocations beyond that are allocated the normal way
by advancing sbrk.

-mental