linux-kernel - Re: [PATCH v3 05/10] drm/v3d: Use huge tmpfs mount point helper

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Message-ID: <20251006090730.364a1713@fedora>
Date: Mon, 6 Oct 2025 09:07:30 +0200
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Loïc Molinari <loic.molinari@...labora.com>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie
 <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Jani Nikula
 <jani.nikula@...ux.intel.com>, Joonas Lahtinen
 <joonas.lahtinen@...ux.intel.com>, Rodrigo Vivi <rodrigo.vivi@...el.com>,
 Tvrtko Ursulin <tursulin@...ulin.net>, Rob Herring <robh@...nel.org>,
 Steven Price <steven.price@....com>, Liviu Dudau <liviu.dudau@....com>,
 Melissa Wen <mwen@...lia.com>, Maíra Canal
 <mcanal@...lia.com>, Hugh Dickins <hughd@...gle.com>, Baolin Wang
 <baolin.wang@...ux.alibaba.com>, Andrew Morton <akpm@...ux-foundation.org>,
 Al Viro <viro@...iv.linux.org.uk>, Mikołaj Wasiak
 <mikolaj.wasiak@...el.com>, Christian Brauner <brauner@...nel.org>, Nitin
 Gote <nitin.r.gote@...el.com>, Andi Shyti <andi.shyti@...ux.intel.com>,
 Christopher Healy <healych@...zon.com>, linux-kernel@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
 linux-mm@...ck.org, kernel@...labora.com
Subject: Re: [PATCH v3 05/10] drm/v3d: Use huge tmpfs mount point helper

On Sat,  4 Oct 2025 11:30:48 +0200
Loïc Molinari <loic.molinari@...labora.com> wrote:

> +static void
> +v3d_huge_mnt_init(struct v3d_dev *v3d)
> +{
> +	int err;
> +
> +	/*
> +	 * By creating our own shmemfs mountpoint, we can pass in
> +	 * mount flags that better match our usecase. However, we
> +	 * only do so on platforms which benefit from it.
> +	 */
> +	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
> +		goto err;
> +
> +	/* The user doesn't want to enable Super Pages */
> +	if (!super_pages)
> +		goto err;
> +
> +	err = drm_gem_huge_mnt_create(&v3d->drm, "within_size");
> +	if (err && err != -EEXIST)
> +		goto err;
> +
> +	drm_info(&v3d->drm, "Using Transparent Hugepages\n");
> +
> +	return;
> +
> +err:
> +	drm_notice(&v3d->drm,
> +		   "Transparent Hugepage support is recommended for optimal performance on this platform!\n");

With the changes suggested on patch 3, this can be shrunk a little bit:

	int err = 0;

	if (super_pages)
		err = drm_gem_huge_mnt_create(&v3d->drm, "within_size");

	if (v3d->drm.huge_mnt)
		drm_info(&v3d->drm, "Using Transparent Hugepages\n");
	else if (!err)
		drm_notice(&v3d->drm,
			   "Transparent Hugepage support is recommended for optimal performance on this platform!\n");
	else
		drm_warn(&v3d->drm, "Couldn't create THP mount point (err=%d)\n", err);