[Intel-gfx] [PATCH v3 07/12] drm/i915/gt: Pipelined page migration

[Matthew Auld]

On 14/06/2021 17:26, Thomas Hellström wrote:
> From: Chris Wilson <chris at chris-wilson.co.uk>
> 
> If we pipeline the PTE updates and then do the copy of those pages
> within a single unpreemptible command packet, we can submit the copies
> and leave them to be scheduled without having to synchronously wait
> under a global lock. In order to manage migration, we need to
> preallocate the page tables (and keep them pinned and available for use
> at any time), causing a bottleneck for migrations as all clients must
> contend on the limited resources. By inlining the ppGTT updates and
> performing the blit atomically, each client only owns the PTE while in
> use, and so we can reschedule individual operations however we see fit.
> And most importantly, we do not need to take a global lock on the shared
> vm, and wait until the operation is complete before releasing the lock
> for others to claim the PTE for themselves.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Co-developed-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld at intel.com>