[Intel-gfx] [RFC 00/38] PPGTT dynamic page allocations

[Chris Wilson]

On Tue, Oct 07, 2014 at 06:10:56PM +0100, Michel Thierry wrote:
> This is based on the first 55 patches of Ben's 48b addressing work, taking
> into consideration the latest changes in (mainly aliasing) ppgtt rules.
> 
> Because of these changes in the tree, the first 17 patches of the original
> series are no longer needed, and some patches required more rework than others.
> 
> For GEN8, it has also been extended to work in logical ring submission (lrc)
> mode, as it looks like it will be the preferred mode of operation.
> I also tried to update the lrc code at the same time the ppgtt refactoring
> occurred, leaving only one patch that is exclusively for lrc.
> 
> I'm asking for comments, as this is the foundation for 48b virtual addressing
> in Broadwell. 

I find the lack of activity tracking in the current ppgtt design severely
limiting. We have a number of tests (both igt and mesa) that fail
because the ppgtt pins gtt space for its lifetime. Transitioning the
backing pages to a bo allows us to evict, and even shrink, vm along with
regular objects. Plus the dynamic allocation here has also been
discussed with the idea of sparse allocation of bo... Imo, we want to
use bo (probably based on gemfs) for both.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre