linux-kernel - Re: [PATCH 13/14] staging: android: ion: Do not sync CPU cache on map/unmap

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Date:   Tue, 19 Feb 2019 13:37:44 -0800
From:   Laura Abbott <labbott@...hat.com>
To:     Brian Starkey <Brian.Starkey@....com>,
        "Andrew F. Davis" <afd@...com>
Cc:     Sumit Semwal <sumit.semwal@...aro.org>,
        Liam Mark <lmark@...eaurora.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        "devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>, nd <nd@....com>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH 13/14] staging: android: ion: Do not sync CPU cache on
 map/unmap

On 1/24/19 8:44 AM, Brian Starkey wrote:
> On Thu, Jan 24, 2019 at 10:04:46AM -0600, Andrew F. Davis wrote:
>> On 1/23/19 11:11 AM, Brian Starkey wrote:
> 
> [snip]
> 
>>
>> I'm very new to all this, so any pointers to history in this area are
>> appreciated.
>>
> 
> [snip]
> 
>>
>>> In case you didn't come across it already, the effort which seems to
>>> have gained the most "air-time" recently is
>>> https://github.com/cubanismo/allocator, which is still a userspace
>>> module (perhaps some concepts from there could go into the kernel?),
>>> but makes some attempts at generic constraint solving. It's also not
>>> really moving anywhere at the moment.
>>>
>>
>> Very interesting, I'm going to have to stare at this for a bit.
> 
> In which case, some reading material that might be of interest :-)
> 
> https://www.x.org/wiki/Events/XDC2016/Program/Unix_Device_Memory_Allocation.pdf
> https://www.x.org/wiki/Events/XDC2017/jones_allocator.pdf
> https://lists.freedesktop.org/archives/mesa-dev/2017-November/177632.html
> 
> -Brian
> 

In some respects this is more a question of "what is the purpose
of Ion". Once upon a time, Ion was going to do constraint solving
but that never really happened and I figured Ion would get deprecated.
People keep coming out of the woodwork with new uses for Ion so
its stuck around. This is why I've primarily focused on Ion as a
framework for exposing available memory types to userspace and leave
the constraint solving to someone else, since that's what most
users seem to want out of Ion ("I know I want memory type X please
give it to me"). That's not to say that this was a perfect or
even the correct approach, just what made the most sense based
on users.

Thanks,
Laura