Re: [PATCH v3 10/10] Documentation/gpu/drm-mm: Add THP paragraph to GEM mapping section

[Bagas Sanjaya <bagasdotme@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 1989 bytes --]

On Sat, Oct 04, 2025 at 11:30:53AM +0200, Loïc Molinari wrote:
> @@ -290,7 +292,7 @@ The open and close operations must update the GEM object reference
>  count. Drivers can use the drm_gem_vm_open() and drm_gem_vm_close() helper
>  functions directly as open and close handlers.
>  
> -The fault operation handler is responsible for mapping individual pages
> +The fault operation handlers are responsible for mapping individual pages
>  to userspace when a page fault occurs. Depending on the memory
>  allocation scheme, drivers can allocate pages at fault time, or can
>  decide to allocate memory for the GEM object at the time the object is
> @@ -299,6 +301,19 @@ created.
>  Drivers that want to map the GEM object upfront instead of handling page
>  faults can implement their own mmap file operation handler.
>  
> +In order to reduce page table overhead, if the internal shmem mountpoint
> +"shm_mnt" is configured to use transparent huge pages (for builds with
> +CONFIG_TRANSPARENT_HUGEPAGE enabled) and if the shmem backing store
> +manages to allocate huge pages, faulty addresses within huge pages will
> +be mapped into the tables using the huge page fault handler. In such
> +cases, mmap() user address alignment for GEM objects is handled by
> +providing a custom get_unmapped_area properly forwarding to the shmem
> +backing store. For most drivers, which don't create a huge mountpoint by
> +default or through a module parameter, transparent huge pages can be
> +enabled by either setting the "transparent_hugepage_shmem" kernel
> +parameter or the "/sys/kernel/mm/transparent_hugepage/shmem_enabled"
> +sysfs knob.
> +
>  For platforms without MMU the GEM core provides a helper method
>  drm_gem_dma_get_unmapped_area(). The mmap() routines will call this to get a
>  proposed address for the mapping.
 
LGTM, thanks!

Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>

-- 
An old man doll... just what I always wanted! - Clara

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]