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Message-ID: <fee6476e-3168-4f4f-ae2f-3ef65fe209b0@ursulin.net>
Date: Thu, 20 Nov 2025 09:31:53 +0000
From: Tvrtko Ursulin <tursulin@...ulin.net>
To: Loïc Molinari <loic.molinari@...labora.com>,
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>,
Boris Brezillon <boris.brezillon@...labora.com>,
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>, Jonathan Corbet <corbet@....net>,
Christopher Healy <healych@...zon.com>, Matthew Wilcox
<willy@...radead.org>, Bagas Sanjaya <bagasdotme@...il.com>
Cc: linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
intel-gfx@...ts.freedesktop.org, linux-mm@...ck.org,
linux-doc@...r.kernel.org, kernel@...labora.com
Subject: Re: [PATCH v9 05/11] drm/i915: Use huge tmpfs mountpoint helpers
On 14/11/2025 17:02, Loïc Molinari wrote:
> Make use of the new drm_gem_huge_mnt_create() and
> drm_gem_get_huge_mnt() helpers to avoid code duplication. Now that
> it's just a few lines long, the single function in i915_gemfs.c is
> moved into v3d_gem_shmem.c.
>
> v3:
> - use huge tmpfs mountpoint in drm_device
> - move i915_gemfs.c into i915_gem_shmem.c
>
> v4:
> - clean up mountpoint creation error handling
>
> v5:
> - use drm_gem_has_huge_mnt() helper
>
> v7:
> - include <drm/drm_print.h> in i915_gem_shmem.c
>
> v8:
> - keep logging notice message with CONFIG_TRANSPARENT_HUGEPAGE=n
> - don't access huge_mnt field with CONFIG_TRANSPARENT_HUGEPAGE=n
>
> v9:
> - replace drm_gem_has_huge_mnt() by drm_gem_get_huge_mnt()
> - remove useless ternary op test in selftests/huge_pages.c
>
> Signed-off-by: Loïc Molinari <loic.molinari@...labora.com>
> ---
> drivers/gpu/drm/i915/Makefile | 3 +-
> drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 48 +++++++++----
> drivers/gpu/drm/i915/gem/i915_gemfs.c | 71 -------------------
> drivers/gpu/drm/i915/gem/i915_gemfs.h | 14 ----
> .../gpu/drm/i915/gem/selftests/huge_pages.c | 16 +++--
> drivers/gpu/drm/i915/i915_drv.h | 5 --
> 6 files changed, 47 insertions(+), 110 deletions(-)
> delete mode 100644 drivers/gpu/drm/i915/gem/i915_gemfs.c
> delete mode 100644 drivers/gpu/drm/i915/gem/i915_gemfs.h
>
> diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> index 84ec79b64960..b5a8c0a6b747 100644
> --- a/drivers/gpu/drm/i915/Makefile
> +++ b/drivers/gpu/drm/i915/Makefile
> @@ -169,8 +169,7 @@ gem-y += \
> gem/i915_gem_ttm_move.o \
> gem/i915_gem_ttm_pm.o \
> gem/i915_gem_userptr.o \
> - gem/i915_gem_wait.o \
> - gem/i915_gemfs.o
> + gem/i915_gem_wait.o
> i915-y += \
> $(gem-y) \
> i915_active.o \
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> index 26dda55a07ff..15c2c6fde2ac 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
> @@ -9,14 +9,16 @@
> #include <linux/uio.h>
>
> #include <drm/drm_cache.h>
> +#include <drm/drm_gem.h>
> +#include <drm/drm_print.h>
>
> #include "gem/i915_gem_region.h"
> #include "i915_drv.h"
> #include "i915_gem_object.h"
> #include "i915_gem_tiling.h"
> -#include "i915_gemfs.h"
> #include "i915_scatterlist.h"
> #include "i915_trace.h"
> +#include "i915_utils.h"
>
> /*
> * Move folios to appropriate lru and release the batch, decrementing the
> @@ -497,6 +499,7 @@ static int __create_shmem(struct drm_i915_private *i915,
> resource_size_t size)
> {
> unsigned long flags = VM_NORESERVE;
> + struct vfsmount *huge_mnt;
> struct file *filp;
>
> drm_gem_private_object_init(&i915->drm, obj, size);
> @@ -515,9 +518,9 @@ static int __create_shmem(struct drm_i915_private *i915,
> if (BITS_PER_LONG == 64 && size > MAX_LFS_FILESIZE)
> return -E2BIG;
>
> - if (i915->mm.gemfs)
> - filp = shmem_file_setup_with_mnt(i915->mm.gemfs, "i915", size,
> - flags);
> + huge_mnt = drm_gem_get_huge_mnt(&i915->drm);
> + if (huge_mnt)
> + filp = shmem_file_setup_with_mnt(huge_mnt, "i915", size, flags);
> else
> filp = shmem_file_setup("i915", size, flags);
> if (IS_ERR(filp))
> @@ -644,21 +647,40 @@ i915_gem_object_create_shmem_from_data(struct drm_i915_private *i915,
>
> static int init_shmem(struct intel_memory_region *mem)
> {
> - i915_gemfs_init(mem->i915);
> - intel_memory_region_set_name(mem, "system");
> + struct drm_i915_private *i915 = mem->i915;
>
> - return 0; /* We have fallback to the kernel mnt if gemfs init failed. */
> -}
> + /*
> + * By creating our own shmemfs mountpoint, we can pass in
> + * mount flags that better match our usecase.
> + *
> + * One example, although it is probably better with a per-file
> + * control, is selecting huge page allocations ("huge=within_size").
> + * However, we only do so on platforms which benefit from it, or to
> + * offset the overhead of iommu lookups, where with latter it is a net
> + * win even on platforms which would otherwise see some performance
> + * regressions such a slow reads issue on Broadwell and Skylake.
> + */
>
> -static int release_shmem(struct intel_memory_region *mem)
> -{
> - i915_gemfs_fini(mem->i915);
> - return 0;
> + if (GRAPHICS_VER(i915) < 11 && !i915_vtd_active(i915))
> + goto no_thp;
> +
> + drm_gem_huge_mnt_create(&i915->drm, "within_size");
> + if (drm_gem_get_huge_mnt(&i915->drm))
> + drm_info(&i915->drm, "Using Transparent Hugepages\n");
> + else
> + drm_notice(&i915->drm,
> + "Transparent Hugepage support is recommended for optimal performance%s\n",
> + GRAPHICS_VER(i915) >= 11 ? " on this platform!" :
> + " when IOMMU is enabled!");
> +
> + no_thp:
> + intel_memory_region_set_name(mem, "system");
> +
> + return 0; /* We have fallback to the kernel mnt if huge mnt failed. */
> }
>
> static const struct intel_memory_region_ops shmem_region_ops = {
> .init = init_shmem,
> - .release = release_shmem,
> .init_object = shmem_object_init,
> };
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gemfs.c b/drivers/gpu/drm/i915/gem/i915_gemfs.c
> deleted file mode 100644
> index 1f1290214031..000000000000
> --- a/drivers/gpu/drm/i915/gem/i915_gemfs.c
> +++ /dev/null
> @@ -1,71 +0,0 @@
> -// SPDX-License-Identifier: MIT
> -/*
> - * Copyright © 2017 Intel Corporation
> - */
> -
> -#include <linux/fs.h>
> -#include <linux/mount.h>
> -#include <linux/fs_context.h>
> -
> -#include <drm/drm_print.h>
> -
> -#include "i915_drv.h"
> -#include "i915_gemfs.h"
> -#include "i915_utils.h"
> -
> -void i915_gemfs_init(struct drm_i915_private *i915)
> -{
> - struct file_system_type *type;
> - struct fs_context *fc;
> - struct vfsmount *gemfs;
> - int ret;
> -
> - /*
> - * By creating our own shmemfs mountpoint, we can pass in
> - * mount flags that better match our usecase.
> - *
> - * One example, although it is probably better with a per-file
> - * control, is selecting huge page allocations ("huge=within_size").
> - * However, we only do so on platforms which benefit from it, or to
> - * offset the overhead of iommu lookups, where with latter it is a net
> - * win even on platforms which would otherwise see some performance
> - * regressions such a slow reads issue on Broadwell and Skylake.
> - */
> -
> - if (GRAPHICS_VER(i915) < 11 && !i915_vtd_active(i915))
> - return;
> -
> - if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
> - goto err;
> -
> - type = get_fs_type("tmpfs");
> - if (!type)
> - goto err;
> -
> - fc = fs_context_for_mount(type, SB_KERNMOUNT);
> - if (IS_ERR(fc))
> - goto err;
> - ret = vfs_parse_fs_string(fc, "source", "tmpfs");
> - if (!ret)
> - ret = vfs_parse_fs_string(fc, "huge", "within_size");
> - if (!ret)
> - gemfs = fc_mount_longterm(fc);
> - put_fs_context(fc);
> - if (ret)
> - goto err;
> -
> - i915->mm.gemfs = gemfs;
> - drm_info(&i915->drm, "Using Transparent Hugepages\n");
> - return;
> -
> -err:
> - drm_notice(&i915->drm,
> - "Transparent Hugepage support is recommended for optimal performance%s\n",
> - GRAPHICS_VER(i915) >= 11 ? " on this platform!" :
> - " when IOMMU is enabled!");
> -}
> -
> -void i915_gemfs_fini(struct drm_i915_private *i915)
> -{
> - kern_unmount(i915->mm.gemfs);
> -}
> diff --git a/drivers/gpu/drm/i915/gem/i915_gemfs.h b/drivers/gpu/drm/i915/gem/i915_gemfs.h
> deleted file mode 100644
> index 16d4333c9a4e..000000000000
> --- a/drivers/gpu/drm/i915/gem/i915_gemfs.h
> +++ /dev/null
> @@ -1,14 +0,0 @@
> -/* SPDX-License-Identifier: MIT */
> -/*
> - * Copyright © 2017 Intel Corporation
> - */
> -
> -#ifndef __I915_GEMFS_H__
> -#define __I915_GEMFS_H__
> -
> -struct drm_i915_private;
> -
> -void i915_gemfs_init(struct drm_i915_private *i915);
> -void i915_gemfs_fini(struct drm_i915_private *i915);
> -
> -#endif
> diff --git a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
> index bd08605a1611..28aef75630a2 100644
> --- a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
> +++ b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
> @@ -1316,7 +1316,7 @@ typedef struct drm_i915_gem_object *
>
> static inline bool igt_can_allocate_thp(struct drm_i915_private *i915)
> {
> - return i915->mm.gemfs && has_transparent_hugepage();
> + return !!drm_gem_get_huge_mnt(&i915->drm);
> }
>
> static struct drm_i915_gem_object *
> @@ -1761,7 +1761,9 @@ static int igt_tmpfs_fallback(void *arg)
> struct drm_i915_private *i915 = arg;
> struct i915_address_space *vm;
> struct i915_gem_context *ctx;
> - struct vfsmount *gemfs = i915->mm.gemfs;
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> + struct vfsmount *huge_mnt = i915->drm.huge_mnt;
> +#endif
> struct drm_i915_gem_object *obj;
> struct i915_vma *vma;
> struct file *file;
> @@ -1782,10 +1784,12 @@ static int igt_tmpfs_fallback(void *arg)
> /*
> * Make sure that we don't burst into a ball of flames upon falling back
> * to tmpfs, which we rely on if on the off-chance we encounter a failure
> - * when setting up gemfs.
> + * when setting up a huge mountpoint.
> */
>
> - i915->mm.gemfs = NULL;
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> + i915->drm.huge_mnt = NULL;
> +#endif
>
> obj = i915_gem_object_create_shmem(i915, PAGE_SIZE);
> if (IS_ERR(obj)) {
> @@ -1819,7 +1823,9 @@ static int igt_tmpfs_fallback(void *arg)
> out_put:
> i915_gem_object_put(obj);
> out_restore:
> - i915->mm.gemfs = gemfs;
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> + i915->drm.huge_mnt = huge_mnt;
> +#endif
Apart from this layering violation in the selftest, this version looks
good to me. I am just wondering if we could somehow improve this aspect.
I was thinking a self-test builds only special version of
i915_gem_object_create_shmem. Call chain is deep but there are flags
passed on:
i915_gem_object_create_shmem
i915_gem_object_create_region
__i915_gem_object_create_region
err = mem->ops->init_object(
So we could add a new helper like:
selftests_create_shmem
i915_gem_object_create_region(...flags =
I915_BO_ALLOC_SELFTESTS_NOTHP...)
And in __create_shmem we just make it:
...
huge_mnt = drm_gem_get_huge_mnt(&i915->drm) &&
if (IS_ENABLED(..SELFTESTS..) &&
(flags & I915_BO_ALLOC_SELFTESTS_NOTHP))
huge_mnt = NULL;
...
It would avoid the ifdef and needing to play games with the DRM internals.
How does that sound to you?
Regards,
Tvrtko
>
> i915_vm_put(vm);
> out:
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 95f9ddf22ce4..93a5af3de334 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -141,11 +141,6 @@ struct i915_gem_mm {
> */
> atomic_t free_count;
>
> - /**
> - * tmpfs instance used for shmem backed objects
> - */
> - struct vfsmount *gemfs;
> -
> struct intel_memory_region *regions[INTEL_REGION_UNKNOWN];
>
> struct notifier_block oom_notifier;
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