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Subject: Re: Why do we let munmap fail?
References: <CAKOZuetOD6MkGPVvYFLj5RXh200FaDyu3sQqZviVRhTFFS3fjA@mail.gmail.com>
From: Dave Hansen <dave.hansen@intel.com>
Message-ID: <aacd607f-4a0d-2b0a-d8d9-b57c686d24fc@intel.com>
Date: Mon, 21 May 2018 15:12:32 -0700
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Sender: owner-linux-mm@kvack.org
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To: Daniel Colascione <dancol@google.com>, linux-mm@kvack.org
Cc: Tim Murray <timmurray@google.com>, Minchan Kim <minchan@kernel.org>

On 05/21/2018 03:07 PM, Daniel Colascione wrote:
> Now let's return to max_map_count itself: what is it supposed to achieve?
> If we want to limit application kernel memory resource consumption, let's
> limit application kernel memory resource consumption, accounting for it on
> a byte basis the same way we account for other kernel objects allocated on
> behalf of userspace. Why should we have a separate cap just for the VMA
> count?

VMAs consume kernel memory and we can't reclaim them.  That's what it
boils down to.