From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bali.collaboradmins.com (bali.collaboradmins.com [148.251.105.195]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 42DE52DECB4; Mon, 1 Dec 2025 08:39:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.251.105.195 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764578370; cv=none; b=s6OXOcxehYr4tAZaiq1QleUxRSX86EGfTPRF2RrET9vLpA0zIh8hy6ax0WkebEVo0XvK5sTBw6brSZdmekDeZStiXOzkLNWm5WPqiPMV0SH+6OkC/AQ4dnFRs3ofpgzFEP76t4RtKeF8+pgG5seXI0ryWibqY9K1i+LDShwC43E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764578370; c=relaxed/simple; bh=/yEJjkl7mI536u4P1ZljdIoiBzn8hkUDB1We2y+0lF4=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=o+BTyZ6wBPYflc41I2S4KoVLpKbr1WlNe/jttdWjAQz4SPwRuLTpcaa3Y0WB9b9QD5qVnQ65uoxa5TFnhnuPuFqW0M1clLNXMgww3NLs4yMmbV5HZlWBpiM8YmAqmvK4dGx5lnosotlJrOwgb85KQfQHeNLiaXgtC9xSZzNLGr8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b=aa32VnMR; arc=none smtp.client-ip=148.251.105.195 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b="aa32VnMR" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1764578366; bh=/yEJjkl7mI536u4P1ZljdIoiBzn8hkUDB1We2y+0lF4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=aa32VnMRDGNZstcTn0Yk21gz6Bp3VD/2Qpcw8VGcVMwsqhZW+9ROIvypak8/Cgf4A DZaP3ErEeb3EX7nGUwnjFlL/9Ey9o2SewxmdQefgUnajm2HN51Pj2tch2WlWLjfJvX qTZ25Fxoxo5VsZHGk8ob2ADJylVc+clQoGA7A5LbGJIgcy/QZjyWqAyfG9VIrSsHIX YQwt2GVHQRvWFZ1lT3/n0N7UxTrlMc8B2jLv7BU1QE7kn8mSzpwRG3M88ajMbVhp8R OlYZJxcGlftU8cibXYfrHo5G/V/n/5RiOrGELOyT1jOAYnGsmkURlRxSufF4zQrGHp ELUWueVvAn8RQ== Received: from fedora (unknown [IPv6:2a01:e0a:2c:6930:d919:a6e:5ea1:8a9f]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (prime256v1) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bbrezillon) by bali.collaboradmins.com (Postfix) with ESMTPSA id 3676D17E013C; Mon, 1 Dec 2025 09:39:25 +0100 (CET) Date: Mon, 1 Dec 2025 09:39:18 +0100 From: Boris Brezillon To: =?UTF-8?B?TG/Dr2M=?= Molinari Cc: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , Rob Herring , Steven Price , Liviu Dudau , Melissa Wen , =?UTF-8?B?TWHDrXJh?= Canal , Hugh Dickins , Baolin Wang , Andrew Morton , Al Viro , =?UTF-8?B?TWlrb8WCYWo=?= Wasiak , Christian Brauner , Nitin Gote , Andi Shyti , Jonathan Corbet , Christopher Healy , Matthew Wilcox , Bagas Sanjaya , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, kernel@collabora.com Subject: Re: [PATCH v10 10/10] Documentation/gpu/drm-mm: Add THP paragraph to GEM mapping section Message-ID: <20251201093918.4051d21d@fedora> In-Reply-To: <20251128185252.3092-11-loic.molinari@collabora.com> References: <20251128185252.3092-1-loic.molinari@collabora.com> <20251128185252.3092-11-loic.molinari@collabora.com> Organization: Collabora X-Mailer: Claws Mail 4.3.1 (GTK 3.24.51; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Fri, 28 Nov 2025 19:52:52 +0100 Lo=C3=AFc Molinari wrote: > Add a paragraph to the GEM objects mapping section explaining how > transparent huge pages are handled by GEM. >=20 > v4: > - fix wording after huge_pages handler removal >=20 > v6: > - fix wording after map_pages handler removal >=20 > Signed-off-by: Lo=C3=AFc Molinari > Reviewed-by: Bagas Sanjaya Reviewed-by: Boris Brezillon > --- > Documentation/gpu/drm-mm.rst | 22 +++++++++++++++++----- > 1 file changed, 17 insertions(+), 5 deletions(-) >=20 > diff --git a/Documentation/gpu/drm-mm.rst b/Documentation/gpu/drm-mm.rst > index d55751cad67c..d69eab0b4093 100644 > --- a/Documentation/gpu/drm-mm.rst > +++ b/Documentation/gpu/drm-mm.rst > @@ -290,15 +290,27 @@ The open and close operations must update the GEM o= bject 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 > -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 > -created. > +The fault operation handler is responsible for mapping 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 created. > =20 > 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 > +managed to allocate a huge page for a faulty address, the fault handler > +will first attempt to insert that huge page into the VMA before falling > +back to individual page insertion. mmap() user address alignment for GEM > +objects is handled by providing a custom get_unmapped_area file > +operation which forwards 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.