[PATCH] drm/amdgpu: further lower VRAM allocation overhead
Pan, Xinhui
Xinhui.Pan at amd.com
Wed Jul 14 09:41:36 UTC 2021
> 2021年7月14日 16:33，Christian König <ckoenig.leichtzumerken at gmail.com> 写道：
>
> Hi Eric,
>
> feel free to push into amd-staging-dkms-5.11, but please don't push it into amd-staging-drm-next.
>
> The later will just cause a merge failure which Alex needs to resolve manually.
>
> I can take care of pushing to amd-staging-drm-next as soon as that is rebased on latest upstream.
>
> Regards,
> Christian.
>
> Am 13.07.21 um 21:19 schrieb Eric Huang:
>> Hi Christian/Felix,
>>
>> If you don't have objection, it will be pushed into amd-staging-dkms-5.11 and amd-staging-drm-next.
>>
>> Thanks,
>> Eric
>>
>> On 2021-07-13 3:17 p.m., Eric Huang wrote:
>>> For allocations larger than 48MiB we need more than a page for the
>>> housekeeping in the worst case resulting in the usual vmalloc overhead.
>>>
>>> Try to avoid this by assuming the good case and only falling back to the
>>> worst case if this didn't worked.
>>>
>>> Signed-off-by: Christian König <christian.koenig at amd.com>
>>> Signed-off-by: Eric Huang <jinhuieric.huang at amd.com>
>>> Reviewed-by: Felix Kuehling <Felix.Kuehling at amd.com>
>>> ---
>>> drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 71 +++++++++++++++-----
>>> 1 file changed, 53 insertions(+), 18 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>>> index be4261c4512e..ecbe05e1db66 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>>> @@ -361,9 +361,11 @@ static void amdgpu_vram_mgr_virt_start(struct ttm_resource *mem,
>>> static int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
>>> struct ttm_buffer_object *tbo,
>>> const struct ttm_place *place,
>>> + unsigned long num_nodes,
>>> + unsigned long pages_per_node,
>>> struct ttm_resource *mem)
>>> {
>>> - unsigned long lpfn, num_nodes, pages_per_node, pages_left, pages;
>>> + unsigned long lpfn, pages_left, pages;
>>> struct amdgpu_vram_mgr *mgr = to_vram_mgr(man);
>>> struct amdgpu_device *adev = to_amdgpu_device(mgr);
>>> uint64_t vis_usage = 0, mem_bytes, max_bytes;
>>> @@ -393,21 +395,6 @@ static int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
>>> return -ENOSPC;
>>> }
>>> - if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
>>> - pages_per_node = ~0ul;
>>> - num_nodes = 1;
>>> - } else {
>>> -#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>>> - pages_per_node = HPAGE_PMD_NR;
>>> -#else
>>> - /* default to 2MB */
>>> - pages_per_node = 2UL << (20UL - PAGE_SHIFT);
>>> -#endif
>>> - pages_per_node = max_t(uint32_t, pages_per_node,
>>> - mem->page_alignment);
>>> - num_nodes = DIV_ROUND_UP(mem->num_pages, pages_per_node);
>>> - }
>>> -
>>> nodes = kvmalloc_array((uint32_t)num_nodes, sizeof(*nodes),
>>> GFP_KERNEL | __GFP_ZERO);
>>> if (!nodes) {
>>> @@ -435,7 +422,12 @@ static int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
>>> i = 0;
>>> spin_lock(&mgr->lock);
>>> while (pages_left) {
>>> - uint32_t alignment = mem->page_alignment;
>>> + unsigned long alignment = mem->page_alignment;
>>> +
>>> + if (i >= num_nodes) {
>>> + r = -E2BIG;
>>> + goto error;
>>> + }
>>> if (pages >= pages_per_node)
>>> alignment = pages_per_node;
>>> @@ -492,6 +484,49 @@ static int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
>>> return r;
>>> }
>>> +/**
>>> + * amdgpu_vram_mgr_alloc - allocate new range
>>> + *
>>> + * @man: TTM memory type manager
>>> + * @tbo: TTM BO we need this range for
>>> + * @place: placement flags and restrictions
>>> + * @mem: the resulting mem object
>>> + *
>>> + * Allocate VRAM for the given BO.
>>> + */
>>> +static int amdgpu_vram_mgr_alloc(struct ttm_resource_manager *man,
>>> + struct ttm_buffer_object *tbo,
>>> + const struct ttm_place *place,
>>> + struct ttm_resource *mem)
>>> +{
>>> + unsigned long num_nodes, pages_per_node;
>>> + int r;
>>> +
>>> + if (place->flags & TTM_PL_FLAG_CONTIGUOUS)
>>> + return amdgpu_vram_mgr_new(man, tbo, place, 1, ~0ul, mem);
>>> +
>>> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>>> + pages_per_node = HPAGE_PMD_NR;
>>> +#else
>>> + /* default to 2MB */
>>> + pages_per_node = 2UL << (20UL - PAGE_SHIFT);
>>> +#endif
>>> + pages_per_node = max_t(uint32_t, pages_per_node,
>>> + mem->page_alignment);
>>> + num_nodes = DIV_ROUND_UP(mem->num_pages, pages_per_node);
>>> +
>>> + if (sizeof(struct drm_mm_node) * num_nodes > PAGE_SIZE) {
I think this should be < PAGE_SIZE? Otherwise amdgpu_vram_mgr_new always return -E2BIG. Or I am missing something?
But you want one page to save all drm mm nodes in the good case. What if user just create a bunch of small VRAM BO, say, 1 thound of 4KB VRAM BOs.
the system memory usage would change from 24KB to 4MB. I have no strong objection to it as time is more expensive in reality.
>>> + r = amdgpu_vram_mgr_new(man, tbo, place,
>>> + PAGE_SIZE / sizeof(struct drm_mm_node),
>>> + pages_per_node, mem);
>>> + if (r != -E2BIG)
>>> + return r;
>>> + }
>>> +
>>> + return amdgpu_vram_mgr_new(man, tbo, place, num_nodes, pages_per_node,
>>> + mem);
>>> +}
>>> +
>>> /**
>>> * amdgpu_vram_mgr_del - free ranges
>>> *
>>> @@ -693,7 +728,7 @@ static void amdgpu_vram_mgr_debug(struct ttm_resource_manager *man,
>>> }
>>> static const struct ttm_resource_manager_func amdgpu_vram_mgr_func = {
>>> - .alloc = amdgpu_vram_mgr_new,
>>> + .alloc = amdgpu_vram_mgr_alloc,
>>> .free = amdgpu_vram_mgr_del,
>>> .debug = amdgpu_vram_mgr_debug
>>> };
>>
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