Commit c969c5fd authored by Philip Yang's avatar Philip Yang Committed by Alex Deucher
Browse files

drm/amdkfd: Remove prefault before migrating to VRAM 



Prefaulting potentially allocates system memory pages before a
migration. This adds unnecessary overhead. Instead we can skip
unallocated pages in the migration and just point migrate->dst to a
0-initialized VRAM page directly. Then the VRAM page will be inserted
to the PTE. A subsequent CPU page fault will migrate the page back to
system memory.

Signed-off-by: default avatarPhilip Yang <Philip.Yang@amd.com>
Reviewed-by: default avatarFelix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent e1f84eef

drivers/gpu/drm/amd/amdkfd/kfd_migrate.c

+5 −7
Original line number Diff line number Diff line
@@ -322,12 +322,13 @@ svm_migrate_copy_to_vram(struct amdgpu_device *adev, struct svm_range *prange, 
	for (i = j = 0; i < npages; i++) {

		struct page *spage;



		spage = migrate_pfn_to_page(migrate->src[i]);

		if (spage && !is_zone_device_page(spage)) {

		dst[i] = cursor.start + (j << PAGE_SHIFT);

		migrate->dst[i] = svm_migrate_addr_to_pfn(adev, dst[i]);

		svm_migrate_get_vram_page(prange, migrate->dst[i]);

		migrate->dst[i] = migrate_pfn(migrate->dst[i]);



		spage = migrate_pfn_to_page(migrate->src[i]);

		if (spage && !is_zone_device_page(spage)) {

			src[i] = dma_map_page(dev, spage, 0, PAGE_SIZE,

					      DMA_TO_DEVICE);

			r = dma_mapping_error(dev, src[i]);
@@ -522,9 +523,6 @@ svm_migrate_ram_to_vram(struct svm_range *prange, uint32_t best_loc, 
	pr_debug("svms 0x%p [0x%lx 0x%lx] to gpu 0x%x\n", prange->svms,

		 prange->start, prange->last, best_loc);



	/* FIXME: workaround for page locking bug with invalid pages */

	svm_range_prefault(prange, mm, SVM_ADEV_PGMAP_OWNER(adev));



	start = prange->start << PAGE_SHIFT;

	end = (prange->last + 1) << PAGE_SHIFT;

drivers/gpu/drm/amd/amdkfd/kfd_svm.c

+0 −22
Original line number Diff line number Diff line
@@ -3181,28 +3181,6 @@ svm_range_best_prefetch_location(struct svm_range *prange) 
	return best_loc;

}



/* FIXME: This is a workaround for page locking bug when some pages are

 * invalid during migration to VRAM

 */

void svm_range_prefault(struct svm_range *prange, struct mm_struct *mm,

			void *owner)

{

	struct hmm_range *hmm_range;

	int r;



	if (prange->validated_once)

		return;



	r = amdgpu_hmm_range_get_pages(&prange->notifier, mm, NULL,

				       prange->start << PAGE_SHIFT,

				       prange->npages, &hmm_range,

				       false, true, owner);

	if (!r) {

		amdgpu_hmm_range_get_pages_done(hmm_range);

		prange->validated_once = true;

	}

}



/* svm_range_trigger_migration - start page migration if prefetch loc changed

 * @mm: current process mm_struct

 * @prange: svm range structure

drivers/gpu/drm/amd/amdkfd/kfd_svm.h

+0 −2
Original line number Diff line number Diff line
@@ -181,8 +181,6 @@ void schedule_deferred_list_work(struct svm_range_list *svms); 
void svm_range_dma_unmap(struct device *dev, dma_addr_t *dma_addr,

			 unsigned long offset, unsigned long npages);

void svm_range_free_dma_mappings(struct svm_range *prange);

void svm_range_prefault(struct svm_range *prange, struct mm_struct *mm,

			void *owner);

int svm_range_get_info(struct kfd_process *p, uint32_t *num_svm_ranges,

		       uint64_t *svm_priv_data_size);

int kfd_criu_checkpoint_svm(struct kfd_process *p,