Re: [RFC PATCH 6/7] drm/ttm: Introduce a huge page aligning TTM range manager.

["Thomas Hellström (VMware)" <thomas_os@shipmail.org>]

On 11/27/19 11:05 AM, Christian König wrote:
> I don't see the advantage over just increasing the alignment 
> requirements in the driver side?

The advantage is that we don't fail space allocation if we can't match 
the alignment. We instead fall back to a lower alignment if it's 
compatible with the GPU required alignment.

Thanks,
/Thomas


>
> That would be a one liner if I'm not completely mistaken.
>
> Regards,
> Christian.
>
> Am 27.11.19 um 09:31 schrieb Thomas Hellström (VMware):
>> From: Thomas Hellstrom <thellstrom@vmware.com>
>>
>> Using huge page-table entries require that the start of a buffer object
>> is huge page size aligned. So introduce a ttm_bo_man_get_node_huge()
>> function that attempts to accomplish this for allocations that are 
>> larger
>> than the huge page size, and provide a new range-manager instance that
>> uses that function.
>>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Michal Hocko <mhocko@suse.com>
>> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
>> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
>> Cc: Ralph Campbell <rcampbell@nvidia.com>
>> Cc: "Jérôme Glisse" <jglisse@redhat.com>
>> Cc: "Christian König" <christian.koenig@amd.com>
>> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
>> ---
>>   drivers/gpu/drm/ttm/ttm_bo_manager.c | 92 ++++++++++++++++++++++++++++
>>   include/drm/ttm/ttm_bo_driver.h      |  1 +
>>   2 files changed, 93 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_bo_manager.c 
>> b/drivers/gpu/drm/ttm/ttm_bo_manager.c
>> index 18d3debcc949..26aa1a2ae7f1 100644
>> --- a/drivers/gpu/drm/ttm/ttm_bo_manager.c
>> +++ b/drivers/gpu/drm/ttm/ttm_bo_manager.c
>> @@ -89,6 +89,89 @@ static int ttm_bo_man_get_node(struct 
>> ttm_mem_type_manager *man,
>>       return 0;
>>   }
>>   +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>> +static int ttm_bo_insert_aligned(struct drm_mm *mm, struct 
>> drm_mm_node *node,
>> +                 unsigned long align_pages,
>> +                 const struct ttm_place *place,
>> +                 struct ttm_mem_reg *mem,
>> +                 unsigned long lpfn,
>> +                 enum drm_mm_insert_mode mode)
>> +{
>> +    if (align_pages >= mem->page_alignment &&
>> +        (!mem->page_alignment || align_pages % mem->page_alignment 
>> == 0)) {
>> +        return drm_mm_insert_node_in_range(mm, node,
>> +                           mem->num_pages,
>> +                           align_pages, 0,
>> +                           place->fpfn, lpfn, mode);
>> +    }
>> +
>> +    return -ENOSPC;
>> +}
>> +
>> +static int ttm_bo_man_get_node_huge(struct ttm_mem_type_manager *man,
>> +                    struct ttm_buffer_object *bo,
>> +                    const struct ttm_place *place,
>> +                    struct ttm_mem_reg *mem)
>> +{
>> +    struct ttm_range_manager *rman = (struct ttm_range_manager *) 
>> man->priv;
>> +    struct drm_mm *mm = &rman->mm;
>> +    struct drm_mm_node *node;
>> +    unsigned long align_pages;
>> +    unsigned long lpfn;
>> +    enum drm_mm_insert_mode mode = DRM_MM_INSERT_BEST;
>> +    int ret;
>> +
>> +    node = kzalloc(sizeof(*node), GFP_KERNEL);
>> +    if (!node)
>> +        return -ENOMEM;
>> +
>> +    lpfn = place->lpfn;
>> +    if (!lpfn)
>> +        lpfn = man->size;
>> +
>> +    mode = DRM_MM_INSERT_BEST;
>> +    if (place->flags & TTM_PL_FLAG_TOPDOWN)
>> +        mode = DRM_MM_INSERT_HIGH;
>> +
>> +    spin_lock(&rman->lock);
>> +    if (IS_ENABLED(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)) {
>> +        align_pages = (HPAGE_PUD_SIZE >> PAGE_SHIFT);
>> +        if (mem->num_pages >= align_pages) {
>> +            ret = ttm_bo_insert_aligned(mm, node, align_pages,
>> +                            place, mem, lpfn, mode);
>> +            if (!ret)
>> +                goto found_unlock;
>> +        }
>> +    }
>> +
>> +    align_pages = (HPAGE_PMD_SIZE >> PAGE_SHIFT);
>> +    if (mem->num_pages >= align_pages) {
>> +        ret = ttm_bo_insert_aligned(mm, node, align_pages, place, mem,
>> +                        lpfn, mode);
>> +        if (!ret)
>> +            goto found_unlock;
>> +    }
>> +
>> +    ret = drm_mm_insert_node_in_range(mm, node, mem->num_pages,
>> +                      mem->page_alignment, 0,
>> +                      place->fpfn, lpfn, mode);
>> +found_unlock:
>> +    spin_unlock(&rman->lock);
>> +
>> +    if (unlikely(ret)) {
>> +        kfree(node);
>> +    } else {
>> +        mem->mm_node = node;
>> +        mem->start = node->start;
>> +    }
>> +
>> +    return 0;
>> +}
>> +#else
>> +#define ttm_bo_man_get_node_huge ttm_bo_man_get_node
>> +#endif
>> +
>> +
>>   static void ttm_bo_man_put_node(struct ttm_mem_type_manager *man,
>>                   struct ttm_mem_reg *mem)
>>   {
>> @@ -154,3 +237,12 @@ const struct ttm_mem_type_manager_func 
>> ttm_bo_manager_func = {
>>       .debug = ttm_bo_man_debug
>>   };
>>   EXPORT_SYMBOL(ttm_bo_manager_func);
>> +
>> +const struct ttm_mem_type_manager_func ttm_bo_manager_huge_func = {
>> +    .init = ttm_bo_man_init,
>> +    .takedown = ttm_bo_man_takedown,
>> +    .get_node = ttm_bo_man_get_node_huge,
>> +    .put_node = ttm_bo_man_put_node,
>> +    .debug = ttm_bo_man_debug
>> +};
>> +EXPORT_SYMBOL(ttm_bo_manager_huge_func);
>> diff --git a/include/drm/ttm/ttm_bo_driver.h 
>> b/include/drm/ttm/ttm_bo_driver.h
>> index cac7a8a0825a..868bd0d4be6a 100644
>> --- a/include/drm/ttm/ttm_bo_driver.h
>> +++ b/include/drm/ttm/ttm_bo_driver.h
>> @@ -888,5 +888,6 @@ int ttm_bo_pipeline_gutting(struct 
>> ttm_buffer_object *bo);
>>   pgprot_t ttm_io_prot(uint32_t caching_flags, pgprot_t tmp);
>>     extern const struct ttm_mem_type_manager_func ttm_bo_manager_func;
>> +extern const struct ttm_mem_type_manager_func ttm_bo_manager_huge_func;
>>     #endif