Re: [PATCH] drm/amdgpu: only use kernel zone if need_dma32 is not required

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Well that we evict here is perfectly intentional.

The laptop I'm typing on actually don't work without this, so please don't touch any of that.

Christian.

Am 12.06.19 um 20:06 schrieb Yang, Philip:
That's kind of hack because dma32 zone is not needed, it has bad effect
to trigger unnecessary eviction for KFDTest.BigBufStressTest. But
ttm_bo_global_init->ttm_mem_global_init always create dma32 zone without
accepting any parameter.

To avoid ttm_mem_global_alloc_page account to dma32 zone, another option
is to add a new flag to ttm_operation_ctx->flags, that looks not good
either.

Thanks,
Philip

On 2019-06-12 1:23 p.m., Kuehling, Felix wrote:
TTM itself has some logic for need_dma32 and TTM_PAGE_FLAG_DMA32. I
believe that should already handle this. need_dma32 is passed from
amdgpu to ttm_bo_device_init to bdev->need_dma32. ttm_tt_create
translates that to page_flags |= TTM_PAGE_FLAG_DMA32 and passes that to
bdev->driver->ttm_tt_create. The two page allocators in ttm_page_alloc.c
and ttm_page_alloc_dma.c check ttm->page_flags. Is that chain broken
somewhere? Overriding glob->mem_glob->num_zones from amdgpu seems to be
a bit of a hack.

Regards,
     Felix

On 2019-06-12 8:13, Yang, Philip wrote:
TTM create two zones, kernel zone and dma32 zone for system memory. If
system memory address allocated is below 4GB, this account to dma32 zone
and will exhaust dma32 zone and trigger unnesssary TTM eviction.

Patch "drm/ttm: Account for kernel allocations in kernel zone only" only
handle the allocation for acc_size, the system memory page allocation is
through ttm_mem_global_alloc_page which still account to dma32 zone if
page is below 4GB.

Change-Id: I289b85d891b8f64a1422c42b1eab398098ab7ef7
Signed-off-by: Philip Yang <Philip.Yang@xxxxxxx>
---
    drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 4 ++++
    1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 2778ff63d97d..79bb9dfe617b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1686,6 +1686,10 @@ int amdgpu_ttm_init(struct amdgpu_device *adev)
    	}
    	adev->mman.initialized = true;
+ /* Only kernel zone (no dma32 zone) if device does not require dma32 */
+	if (!adev->need_dma32)
+		adev->mman.bdev.glob->mem_glob->num_zones = 1;
+
    	/* We opt to avoid OOM on system pages allocations */
    	adev->mman.bdev.no_retry = true;
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