[Linaro-mm-sig] Memory Management Discussion

Jordan Crouse jcrouse at codeaurora.org
Wed Apr 20 15:13:51 UTC 2011


On 04/19/2011 10:12 PM, Zach Pfeffer wrote:
> Speaking of Graphics and Multimedia - we may want to discuss IOMMU
> APIs and distributed memory management. These devices are becoming
> more prevalent and having a standard way of working with them would be
> useful.
>
> I did a little of this work at Qualcomm and pushed some soundly
> rejected patches to the kernel, see "mm: iommu: An API to unify IOMMU,
> CPU and device memory management."
>
> -Zach

As we talked during the meeting at ELC, IOMMU is important, but I think that there
is broad agreement to consolidate (eventually) on the standard APIs.  I still think
that the memory allocation problem is the more interesting one because it affects
everybody equally, MMU or not.  Not that I want to shut down debate or anything,
I just don't want to distract us from the larger problem that we face.

Jordan

> On 19 April 2011 20:52, Clark, Rob<rob at ti.com>  wrote:
>> On Mon, Apr 18, 2011 at 9:45 AM, Sree Kumar<sreeon at gmail.com>  wrote:
>>> Thanks Jesse for initiating the mailing list.
>>>
>>> We need to address the requirements of Graphics and Multimedia Accelerators
>>> (IPs).
>>> What we really need is a permanent solution (at upstream) which accommodates
>>> the following requirements and conforms to Graphics and Multimedia use
>>> cases.
>>>
>>> 1.Mechanism to map/unmap the memory. Some of the IPs’ have the ability to
>>> address virtual memory and some can address only physically contiguous
>>> address space. We need to address both these cases.
>>> 2.Mechanism to allocate and release memory.
>>> 3.Method to share the memory (ZERO copy is a MUST for better performance)
>>> between different device drivers (example output of camera to multimedia
>>> encoder).
>>> 4.Method to share the memory with different processes in userspace. The
>>> sharing mechanism should include built-in security features.
>>>
>>> Are there any special requirements from V4L or DRM perspectives?
>>
>>  From DRI perspective.. I guess the global buffer name is restricted to
>> a 4 byte integer, unless you change the DRI proto..
>>
>> Authentication hooks for the driver (on x11 driver side) are for a
>> single authentication covering all buffers shared between client and
>> server, and is done by 4 byte token exchange between client and
>> server.  I've not had time yet to look more closely at the
>> authentication aspect of ION.
>>
>> Those are just things off the top of my head, hopefully someone else
>> from X11 world chimes in with whatever else I missed.  But I guess
>> most important thing is whether or not it can fit within existing DRI
>> protocol.  If it does, then the drivers on client and server side
>> could use whatever..
>>
>> BR,
>> -R
>>
>>
>>> Thanks,
>>> Sree
>>>
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>>
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-- 
Jordan Crouse
Qualcomm Innovation Center
Qualcomm Innovation Center is a member of Code Aurora Forum



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