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Sat, 04 Oct 2025 15:40:23 -0700 (PDT) Received: from archie.me ([103.124.138.155]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-28e8d111910sm88078525ad.18.2025.10.04.15.40.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 04 Oct 2025 15:40:22 -0700 (PDT) Received: by archie.me (Postfix, from userid 1000) id 835BE4233433; Sun, 05 Oct 2025 05:40:19 +0700 (WIB) Date: Sun, 5 Oct 2025 05:40:19 +0700 From: Bagas Sanjaya To: =?utf-8?B?TG/Dr2M=?= Molinari , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , Boris Brezillon , Rob Herring , Steven Price , Liviu Dudau , Melissa Wen , =?utf-8?B?TWHDrXJh?= Canal , Hugh Dickins , Baolin Wang , Andrew Morton , Al Viro , =?utf-8?Q?Miko=C5=82aj?= Wasiak , Christian Brauner , Nitin Gote , Andi Shyti , Christopher Healy Cc: linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-mm@kvack.org, kernel@collabora.com Subject: Re: [PATCH v3 10/10] Documentation/gpu/drm-mm: Add THP paragraph to GEM mapping section Message-ID: References: <20251004093054.21388-1-loic.molinari@collabora.com> <20251004093054.21388-11-loic.molinari@collabora.com> MIME-Version: 1.0 Content-Type: multipart/signed; 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charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sat, Oct 04, 2025 at 11:30:53AM +0200, Lo=C3=AFc Molinari wrote: > @@ -290,7 +292,7 @@ The open and close operations must update the GEM obj= ect reference > count. Drivers can use the drm_gem_vm_open() and drm_gem_vm_close() help= er > functions directly as open and close handlers. > =20 > -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. > =20 > +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 g= et a > proposed address for the mapping. =20 LGTM, thanks! Reviewed-by: Bagas Sanjaya --=20 An old man doll... just what I always wanted! - Clara --cgdVn3+TYG3JLZOy Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQSSYQ6Cy7oyFNCHrUH2uYlJVVFOowUCaOGiTwAKCRD2uYlJVVFO owsBAP926UwrcUZLpaNBVlMMMAJn+GCE/YTh2qS92wDMr5wDhAD8D6FJXmT5X1j7 e7eeG3goT2uCJaiZG5r1107jYRzKSAs= =vdd1 -----END PGP SIGNATURE----- --cgdVn3+TYG3JLZOy--