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Date: Sat, 20 Oct 2012 15:12:22 -0500
From: Alan Cox <alc@rice.edu>
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To: Poul-Henning Kamp <phk@phk.freebsd.dk>
Subject: Re: Behavior of madvise(MADV_FREE)
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Cc: Tim LaBerge <tlaberge@juniper.net>,
 "freebsd-arch@freebsd.org Arch" <freebsd-arch@FreeBSD.org>,
 Jason Evans <jasone@FreeBSD.org>, Alan Cox <alc@rice.edu>,
 Marcel Moolenaar <marcel@xcllnt.net>
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On 10/20/2012 14:34, Poul-Henning Kamp wrote:
> --------
> In message<5082F0F3.1070102@rice.edu>, Alan Cox writes:
>
>> I'm sympathetic.  Once upon a time, I was often called upon to explain
>> to network administrators why their idle web cache didn't have oodles of
>> "free" memory and how this wasn't a problem.
> You too ?   :-)
>
>> I think that you're being a bit too pessimistic here.  If your use case
>> really corresponds to "this memory is free and will not be reused (or
>> reallocated for a very long time)"
> Which brings me to a question I have wondered:  Why not simply
> munmap(2) it until you need it again ?
>

My recollection is that Marcel said that the memory was acquired via 
sbrk(2).