From: Preben Randhol <randhol+news@pvv.org>
Subject: Re: Array and memory usage
Date: Sun, 9 Mar 2003 17:09:16 +0000 (UTC)
Date: 2003-03-09T17:09:16+00:00 [thread overview]
Message-ID: <slrnb6mt70.1lm.randhol+news@kiuk0152.chembio.ntnu.no> (raw)
In-Reply-To: EuKaa.21763$eG2.3707@sccrnsc03
Jeffrey Creem wrote:
>
> I believe what you are seeing is not something that will happen under all
> OS's.
>
> Linux uses a commit-on-us type memory manager. Even though you initialized
> your data, it probably was done in such a way that the memory was intialized
> within the ELF initialized data segment.
>
> Under linux even something like
>
> aa = malloc(A_BIG_NUMBER)
>
> will not show all of the data as actually allocated until a process accesses
> each page of memory..
>
> What you are seeing is partially a trick and partially real. It is not a
> direct effect of the language or compiler.
>
> Whether or not you should write your programs to rely on it will depend on
> many factors.
>
> Certainly on an embedded OS like vxWorks, your memory would be allocated and
> consumed immediately.
OK Thanks for clearing it up. I saw the effect last night so I decided
it was time for sleep as I thought I had done something else wrong. But
when I saw the same effect today I started wondering what the effect
was.
At any rate I think I'll stick with an array and set it to some number
that can be changed if needed. We are not talking about a lot of bytes
anyway :-)
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next prev parent reply other threads:[~2003-03-09 17:09 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-03-09 11:19 Array and memory usage Preben Randhol
2003-03-09 11:52 ` John R. Strohm
2003-03-09 12:11 ` Preben Randhol
2003-03-09 13:34 ` Marin David Condic
2003-03-09 15:05 ` Preben Randhol
2003-03-10 1:45 ` Mark Biggar
2003-03-10 11:57 ` Marin David Condic
2003-03-10 12:06 ` Jeffrey Creem
2003-03-09 17:49 ` Robert A Duff
2003-03-09 17:04 ` Jeffrey Creem
2003-03-09 17:09 ` Preben Randhol [this message]
2003-03-09 18:10 ` Robert A Duff
2003-03-10 15:13 ` Matthew Heaney
2003-03-10 23:33 ` Robert A Duff
2003-03-11 0:40 ` Randy Brukardt
2003-03-11 23:37 ` Robert A Duff
2003-03-12 19:18 ` Randy Brukardt
2003-03-11 16:01 ` Matthew Heaney
2003-03-11 17:38 ` Warren W. Gay VE3WWG
-- strict thread matches above, loose matches on Subject: below --
2003-03-12 22:04 Alexandre E. Kopilovitch
2003-03-12 22:20 ` Larry Kilgallen
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