way to allocate memory within a range ?

way to allocate memory within a range ?

[Auguste Mome]

Hello,
I'd like to use kmem_cache() system, but need the memory taken from a
specific range if requested, outside the range otherwise.
I think about adding new zone and define new GFP flag to either select or
ignore the zone. Does it sound possible? Then I welcome any hint if you know
where to add the appropriated test in allocator, how to attach the
region to the new zone id).

Or slab/slub system is not designed for this, I should forget it and
opt for another system?

August.

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Re: way to allocate memory within a range ?

[David Rientjes]

On Wed, 24 Feb 2010, Auguste Mome wrote:

> I'd like to use kmem_cache() system, but need the memory taken from a
> specific range if requested, outside the range otherwise.
> I think about adding new zone and define new GFP flag to either select or
> ignore the zone. Does it sound possible? Then I welcome any hint if you know
> where to add the appropriated test in allocator, how to attach the
> region to the new zone id).
> 
> Or slab/slub system is not designed for this, I should forget it and
> opt for another system?
> 

No slab allocator is going to be designed for that other than SLAB_DMA to 
allocate from lowmem.  If you don't have need for lowmem, why do you need 
memory only from a certain range?  I can imagine it would have a usecase 
for memory hotplug to avoid allocating slab that cannot be reclaimed on 
certain nodes, but ZONE_MOVABLE seems more appropriate to guarantee such 
migration properties.

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Re: way to allocate memory within a range ?

[KAMEZAWA Hiroyuki]

On Wed, 24 Feb 2010 01:46:49 +0100
Auguste Mome <augustmome@gmail.com> wrote:

> Hello,
> I'd like to use kmem_cache() system, but need the memory taken from a
> specific range if requested, outside the range otherwise.
> I think about adding new zone and define new GFP flag to either select or
> ignore the zone. Does it sound possible? Then I welcome any hint if you know
> where to add the appropriated test in allocator, how to attach the
> region to the new zone id).
> 
> Or slab/slub system is not designed for this, I should forget it and
> opt for another system?
> 
I think you can find adding a new zone is very hard.
please forget.

But for what purpose you want to specifiy phyiscal address of memory ?

Thanks,
-Kame

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Re: way to allocate memory within a range ?

[Christoph Lameter]

On Tue, 23 Feb 2010, David Rientjes wrote:

> > Or slab/slub system is not designed for this, I should forget it and
> > opt for another system?
> >
>
> No slab allocator is going to be designed for that other than SLAB_DMA to
> allocate from lowmem.  If you don't have need for lowmem, why do you need
> memory only from a certain range?  I can imagine it would have a usecase
> for memory hotplug to avoid allocating slab that cannot be reclaimed on
> certain nodes, but ZONE_MOVABLE seems more appropriate to guarantee such
> migration properties.

Awhile ago I posted a patch to do just that. It was called
alloc_pages_range() and the intend was to replace the dma zone.

http://lkml.indiana.edu/hypermail/linux/kernel/0609.2/2096.html

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Re: way to allocate memory within a range ?

[Auguste Mome]

OK thanks for your comments, I found that mempool() API can do the job
I need, because
I can live with a fixed size for allocated object, so I plan to
populate the pool by adding all the
"cells" of the given range.
My use case is another module aside Linux that would map the the same
memory area.

August.

On Wed, Feb 24, 2010 at 4:35 PM, Christoph Lameter
<cl@linux-foundation.org> wrote:
> On Tue, 23 Feb 2010, David Rientjes wrote:
>
>> > Or slab/slub system is not designed for this, I should forget it and
>> > opt for another system?
>> >
>>
>> No slab allocator is going to be designed for that other than SLAB_DMA to
>> allocate from lowmem.  If you don't have need for lowmem, why do you need
>> memory only from a certain range?  I can imagine it would have a usecase
>> for memory hotplug to avoid allocating slab that cannot be reclaimed on
>> certain nodes, but ZONE_MOVABLE seems more appropriate to guarantee such
>> migration properties.
>
> Awhile ago I posted a patch to do just that. It was called
> alloc_pages_range() and the intend was to replace the dma zone.
>
> http://lkml.indiana.edu/hypermail/linux/kernel/0609.2/2096.html
>
>

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