linux-kernel - Re: [PATCH, RFD]: Unbreak no-mmu mmap

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Date:	Mon, 11 Jun 2007 19:22:02 -0400
From:	"Mike Frysinger" <vapier.adi@...il.com>
To:	"Bernd Schmidt" <bernds_cb1@...nline.de>
Cc:	"Matt Mackall" <mpm@...enic.com>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"David Howells" <dhowells@...hat.com>,
	"Wu, Bryan" <Bryan.Wu@...log.com>,
	"Greg Ungerer" <gerg@...pgear.com>
Subject: Re: [PATCH, RFD]: Unbreak no-mmu mmap

On 6/11/07, Bernd Schmidt <bernds_cb1@...nline.de> wrote:
> Mike Frysinger wrote:
> > On 6/9/07, Matt Mackall <mpm@...enic.com> wrote:
> >> On Fri, Jun 08, 2007 at 03:53:49PM +0200, Bernd Schmidt wrote:
> >> > 2. It is no longer possible to get blocks smaller than a page through
> >> >    mmap.  This behaviour was used by simplemalloc, which is an insane
> >> >    way of implementing malloc on nommu systems and hopefully not used
> >> >    by anyone anymore.
> >>
> >> That's worrisome. Breaking existing apps/libraries seems like a bad
> >> idea.
> >
> > it isnt breaking anything ... simplemalloc() will continue to execute
> > in newer kernels
>
> While that's true, it'll have an even bigger memory overhead than it
> already does (simplemalloc, by trapping into the kernel and creating
> vm_area/vm_list structures for every malloc call, has huge overheads in
> both time and space).

yes, it does increase the runtime overhead, but the simplemalloc
implementation is already tagged as crappy, so i dont think it's that
big of a deal ... especially in light of all of the advantages the
other malloc implementation gets us nommu peeps
-mike
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