On 29/03/22 4:54 pm, Christian König wrote:
> Am 29.03.22 um 13:19 schrieb Arunpravin Paneer Selvam:
>> [SNIP]
>>>> + pages_left = node->base.num_pages;
>>>>
>>>> i = 0;
>>>> - spin_lock(&mgr->lock);
>>>> while (pages_left) {
>>>> - uint32_t alignment = tbo->page_alignment;
>>>> + if (tbo->page_alignment)
>>>> + min_page_size = tbo->page_alignment << PAGE_SHIFT;
>>>> + else
>>>> + min_page_size = mgr->default_page_size;
>>> The handling here looks extremely awkward to me.
>>>
>>> min_page_size should be determined outside of the loop, based on
>>> default_page_size, alignment and contiguous flag.
>> I kept min_page_size determine logic inside the loop for cases 2GiB+
>> requirements, Since now we are round up the size to the required
>> alignment, I modified the min_page_size determine logic outside of the
>> loop in v12. Please review.
>
> Ah! So do we only have the loop so that each allocation isn't bigger
> than 2GiB? If yes couldn't we instead add a max_alloc_size or something
> similar?
yes we have the loop to limit the allocation not bigger than 2GiB, I
think we cannot avoid the loop since we need to allocate the remaining
pages if any, to complete the 2GiB+ size request. In other words, first
iteration we limit the max size to 2GiB and in the second iteration we
allocate the left over pages if any.
>
> BTW: I strongly suggest that you rename min_page_size to min_alloc_size.
> Otherwise somebody could think that those numbers are in pages and not
> bytes.
modified in v12
>
>>> Then why do you drop the lock and grab it again inside the loop? And what
>>> is "i" actually good for?
>> modified the lock/unlock placement in v12.
>>
>> "i" is to track when there is 2GiB+ contiguous allocation request, first
>> we allocate 2GiB (due to SG table limit) continuously and the remaining
>> pages in the next iteration, hence this request can't be a continuous.
>> To set the placement flag we make use of "i" value. In our case "i"
>> value becomes 2 and we don't set the below flag.
>> node->base.placement |= TTM_PL_FLAG_CONTIGUOUS;
>>
>> If we don't get such requests, I will remove "i".
>
> I'm not sure if that works.
>
> As far as I can see drm_buddy_alloc_blocks() can allocate multiple
> blocks at the same time, but i is only incremented when we loop.
>
> So what you should do instead is to check if node->blocks just contain
> exactly one element after the allocation but before the trim.
ok
>
>>>> +
>>>> + /* Limit maximum size to 2GB due to SG table limitations */
>>>> + pages = min(pages_left, 2UL << (30 - PAGE_SHIFT));
>>>>
>>>> if (pages >= pages_per_node)
>>>> - alignment = pages_per_node;
>>>> -
>>>> - r = drm_mm_insert_node_in_range(mm, &node->mm_nodes[i], pages,
>>>> - alignment, 0, place->fpfn,
>>>> - lpfn, mode);
>>>> - if (unlikely(r)) {
>>>> - if (pages > pages_per_node) {
>>>> - if (is_power_of_2(pages))
>>>> - pages = pages / 2;
>>>> - else
>>>> - pages = rounddown_pow_of_two(pages);
>>>> - continue;
>>>> - }
>>>> - goto error_free;
>>>> + min_page_size = pages_per_node << PAGE_SHIFT;
>>>> +
>>>> + if (!is_contiguous && !IS_ALIGNED(pages, min_page_size >>
>>>> PAGE_SHIFT))
>>>> + is_contiguous = 1;
>>>> +
>>>> + if (is_contiguous) {
>>>> + pages = roundup_pow_of_two(pages);
>>>> + min_page_size = pages << PAGE_SHIFT;
>>>> +
>>>> + if (pages > lpfn)
>>>> + lpfn = pages;
>>>> }
>>>>
>>>> - vis_usage += amdgpu_vram_mgr_vis_size(adev, &node->mm_nodes[i]);
>>>> - amdgpu_vram_mgr_virt_start(&node->base, &node->mm_nodes[i]);
>>>> - pages_left -= pages;
>>>> + BUG_ON(min_page_size < mm->chunk_size);
>>>> +
>>>> + mutex_lock(&mgr->lock);
>>>> + r = drm_buddy_alloc_blocks(mm, (u64)place->fpfn << PAGE_SHIFT,
>>>> + (u64)lpfn << PAGE_SHIFT,
>>>> + (u64)pages << PAGE_SHIFT,
>>>> + min_page_size,
>>>> + &node->blocks,
>>>> + node->flags);
>>>> + mutex_unlock(&mgr->lock);
>>>> + if (unlikely(r))
>>>> + goto error_free_blocks;
>>>> +
>>>> ++i;
>>>>
>>>> if (pages > pages_left)
>>>> - pages = pages_left;
>>>> + pages_left = 0;
>>>> + else
>>>> + pages_left -= pages;
>>>> }
>>>> - spin_unlock(&mgr->lock);
>>>>
>>>> - if (i == 1)
>>>> + /* Free unused pages for contiguous allocation */
>>>> + if (is_contiguous) {
>>> Well that looks really odd, why is trimming not part of
>>> drm_buddy_alloc_blocks() ?
>> we didn't place trim function part of drm_buddy_alloc_blocks since we
>> thought this function can be a generic one and it can be used by any
>> other application as well. For example, now we are using it for trimming
>> the last block in case of size non-alignment with min_page_size.
>
> Good argument. Another thing I just realized is that we probably want to
> double check if we only allocated one block before the trim.
ok
>
> Thanks,
> Christian.
>
