Here , checking place->lpfn , is that mean if required place is located in 
visible vram, driver run none pages split code path?
Yes, exactly. CPU accessible allocations weren't meant to be split with the initial implementation.

For this we need to be able map scattered allocations into the CPU VM page tables first.

You kind of implemented this, but it would still cause a ping/pong of the BO inside the visible VRAM space.

We would need to move the handling of AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED from amdgpu_ttm_placement_init() down into the VRAM manager as well.

Regards,
Christian.

Am 07.11.2016 um 03:10 schrieb Qu, Jim:
HI Christian:

         if (bo->flags & AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS ||
-           amdgpu_vram_page_split == -1) {
+           place->lpfn || amdgpu_vram_page_split == -1) {
                 pages_per_node = ~0ul;
                 num_nodes = 1;
         } else {

Here , checking place->lpfn , is that mean if required place is located in 
visible vram, driver run none pages split code path?
if so, seem it comes back to the starting point. In extreme cases, allocate 
visible vram fail.

Thanks
JimQu

________________________________________
发件人: amd-gfx <[email protected]> 代表 Christian König 
<[email protected]>
发送时间: 2016年11月4日 19:00
收件人: [email protected]
主题: [PATCH 1/2] drm/amdgpu: disable the VRAM manager on special placements v2

From: Christian König <[email protected]>

This disables the VRAM manager when a special placement is requested, otherwise
we play ping/pong with the buffers on every command submission.

v2: only check lpfn

Signed-off-by: Christian König <[email protected]>
---
  drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
index 180eed7c..d710226 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
@@ -108,7 +108,7 @@ static int amdgpu_vram_mgr_new(struct ttm_mem_type_manager 
*man,
                 lpfn = man->size;

         if (bo->flags & AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS ||
-           amdgpu_vram_page_split == -1) {
+           place->lpfn || amdgpu_vram_page_split == -1) {
                 pages_per_node = ~0ul;
                 num_nodes = 1;
         } else {
--
2.5.0

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