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

Bernd Schmidt
2007-06-11T23:04:25Z

Mike Frysinger wrote:
> On 6/9/07, Matt Mackall <mpm@selenic.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).
I've posted this as an RFD to get a feeling for whether we can change
behaviour here - I do expect that nommu embedded systems are less
constrained by backwards compatibility considerations, but I'd like to
hear from other embedded users whether this is a change they'd welcome.

Bernd
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