[v4,0/8] drm/v3d: Enable Big and Super Pages

Message

Maíra Canal April 28, 2024, 12:40 p.m. UTC

This series introduces support for big and super pages in V3D. The V3D MMU has
support for 64KB and 1MB pages, called big pages and super pages, which are
currently not used. Therefore, this patchset has the intention to enable big and
super pages in V3D. The advantage of enabling big and super pages is that if any
entry for a page within a big/super page is cached in the MMU, it will be used
for the translation of all virtual addresses in the range of that super page
without requiring fetching any other entries.

Big/Super pages essentially mean a slightly better performance for users,
especially in applications with high memory requirements (e.g. applications
that use multiple large BOs).

Using a Raspberry Pi 4 (with a PAGE_SIZE=4KB downstream kernel), when running
traces from multiple applications, we were able to see the following
improvements:

fps_avg  helped:  warzone2100.70secs.1024x768.trace:                    1.98 -> 2.42     (22.19%) (v1: 2.56)
fps_avg  helped:  warzone2100.30secs.1024x768.trace:                    2 -> 2.45        (21.96%) (v1: 2.39)
fps_avg  helped:  supertuxkart-menus_1024x768.trace:                    123.12 -> 128.39 (4.28%)  (v1: 125.50)
fps_avg  helped:  vkQuake_capture_frames_1_through_1200_1280x720.gfxr:  61.26 -> 62.89   (2.67%)  (v1: 61.36)
fps_avg  helped:  quake2-gles3-1280x720.trace:                          63.42 -> 64.86   (2.27%)  (v1: 64.29)
fps_avg  helped:  ue4_sun_temple_640x480.gfxr:                          25.15 -> 25.63   (1.89%)  (v1: 24.94)
fps_avg  helped:  ue4_shooter_game_high_quality_640x480.gfxr:           19.28 -> 19.61   (1.72%)  (v1: 19.02)
fps_avg  helped:  ue4_shooter_game_shooting_high_quality_640x480.gfxr:  23.58 -> 23.91   (1.39%)  (v1: 23.34)
fps_avg  helped:  quake3e_capture_frames_1_through_1800_1920x1080.gfxr: 61.40 -> 62.00   (0.96%)  (v1: -)
fps_avg  helped:  serious_sam_trace02_1280x720.gfxr:                    49.41 -> 49.84   (0.86%)  (v1: 47.74)
fps_avg  helped:  supertuxkart-racing_1024x768.trace:                   8.69 -> 8.74     (0.56%)  (v1: -)
fps_avg  helped:  sponza_demo01_800x600.gfxr:                           17.55 -> 17.64   (0.50%)  (v1: -)
fps_avg  helped:  quake2-gl1.4-1280x720.trace:                          36.43 -> 36.58   (0.43%)  (v1: 36.57)
fps_avg  helped:  quake3e-1280x720.trace:                               94.49 -> 94.87   (0.40%)  (v1: -)
fps_avg  helped:  sponza_demo02_800x600.gfxr:                           19.79 -> 19.87   (0.39%)  (v1: -)

Using a Raspberry Pi 5 (with a PAGE_SIZE=16KB downstream kernel), when running
traces from multiple applications, we were able to see the following
improvements:

fps_avg  helped:  warzone2100.30secs.1024x768.trace:                       4.40 -> 4.95     (12.58%) (v1: 4.49)
fps_avg  helped:  vkQuake_capture_frames_1_through_1200_1280x720.gfxr:     135.05 -> 141.21 (4.56%)  (v1: 139.45)
fps_avg  helped:  supertuxkart-menus_1024x768.trace:                       291.73 -> 302.05 (3.54%)  (v1: 303.80)
fps_avg  helped:  quake2-gles3-1280x720.trace:                             148.90 -> 153.57 (3.13%)  (v1: 156.13)
fps_avg  helped:  quake2-gl1.4-1280x720.trace:                             82.60 -> 84.46   (2.25%)  (v1: -)
fps_avg  helped:  ue4_shooter_game_shooting_low_quality_640x480.gfxr:      49.59 -> 50.54   (1.92%)  (v1: 47.30)
fps_avg  helped:  ue4_shooter_game_shooting_high_quality_640x480.gfxr:     51.03 -> 51.93   (1.76%)  (v1: 50.46)
fps_avg  helped:  ue4_shooter_game_high_quality_640x480.gfxr:              31.15 -> 31.64   (1.60%)  (v1: 31.05)
fps_avg  helped:  ue4_sun_temple_640x480.gfxr:                             40.26 -> 40.88   (1.54%)  (v1: 40.23)
fps_avg  helped:  sponza_demo01_800x600.gfxr:                              43.23 -> 43.84   (1.40%)  (v1: 43.68)
fps_avg  helped:  warzone2100.70secs.1024x768.trace:                       4.36 -> 4.42     (1.39%)  (v1: -)
fps_avg  helped:  sponza_demo02_800x600.gfxr:                              48.94 -> 49.51   (1.17%)  (v1: 49.34)
fps_avg  helped:  quake3e_capture_frames_1_through_1800_1920x1080.gfxr:    162.11 -> 163.13 (0.63%)  (v1: 165.71)
fps_avg  helped:  quake3e-1280x720.trace:                                  229.82 -> 231.00 (0.51%)  (v1: 234.51)
fps_avg  helped:  supertuxkart-racing_1024x768.trace:                      20.42 -> 20.48   (0.30%)  (v1: 20.59)
fps_avg  helped:  quake3e_capture_frames_1800_through_2400_1920x1080.gfxr: 157.45 -> 157.61 (0.10%)  (v1: 160.35)
fps_avg  helped:  serious_sam_trace02_1280x720.gfxr:                       59.99 -> 60.02   (0.05%)  (v1: -)

When glancing at the percentage improvement, one might initially perceive v2
as causing a performance downgrade. However, that assumption doesn't hold true.
In the case of v1, we were using downstream kernel version 6.1, whereas now,
with the kernel updated to 6.6 for v2, there's a small uptick in performance.
This indicates an enhancement in the baseline scenario, rather than any detriment
caused by v2. Additionally, I've included stats from v1 in the comparisons. Upon
scrutinizing the average FPS of v2 in contrast to v1, it becomes evident that v2
not only maintains the improvements but may even surpass them.

This version provides a much safer way to iterate through memory and doesn't
hold to the same limitations as v1. For example, v1 had a hard-coded hack that
only allowed a huge page to be created if the BO was bigger than 2MB. These
limitations are gone now.

This series also introduces changes in the GEM helpers, in order to enable V3D
to have a separate mount point for shmfs GEM objects. Any feedback from the
community about the changes in the GEM helpers is welcomed!

v1 -> v2: https://lore.kernel.org/dri-devel/[e-mail]/

* [1/6] Add Iago's R-b to PATCH 1/5 (Iago Toral)
* [2/6] Create a new function `drm_gem_object_init_with_mnt()` to define the
        shmfs mountpoint. Now, we don't touch a bunch of drivers, as
				`drm_gem_object_init()` preserves its signature (Tvrtko Ursulin)
* [3/6] Use `huge=within_size` instead of `huge=always`, in order to avoid OOM.
        This also allow us to move away from the 2MB hack. (Tvrtko Ursulin)
* [3/6] Add Iago's R-b to PATCH 3/5 (Iago Toral)
* [5/6] Create a separate patch to reduce the alignment of the node allocation
        (Iago Toral)
* [6/6] Complete refactoring to the way that we iterate through the memory
        (Tvrtko Ursulin)
* [6/6] Don't use drm_prime_get_contiguous_size(), as it could give us misleading
        data (Tvrtko Ursulin)
* [6/6] Use both Big Pages (64K) and Super Pages (1MB)

v2 -> v3: https://lore.kernel.org/dri-devel/[e-mail]/T/

* [2/8] Add Tvrtko's R-b to PATCH 2/8 (Tvrtko Ursulin)
* [4/8] Add Tvrtko's R-b to PATCH 4/8 (Tvrtko Ursulin)
* [6/8] Now, PATCH 6/8 regards supporting big/super pages when writing out PTEs
        (Tvrtko Ursulin)
* [6/8] s/page_address/pfn (Tvrtko Ursulin)
* [6/8] As `sg_dma_len()` returns `unsigned int`, then `len` must be `unsigned int`
        too (Tvrtko Ursulin)
* [6/8] `i` and `page_size` are `unsigned int` as well (Tvrtko Ursulin)
* [6/8] Move `i`, `page_prot` and `page_size` to the inner scope (Tvrtko Ursulin)
* [6/8] s/pte/page_address/ (Tvrtko Ursulin)
* [7/8] New patch: use gemfs/THP in BO creation if available
* [8/8] New patch: 
* [8/8] Don't expose the modparam `super_pages` unless CONFIG_TRANSPARENT_HUGEPAGE
        is enabled (Tvrtko Ursulin)
* [8/8] Use `v3d->gemfs` to check if the user disabled Super Pages support
        (Tvrtko Ursulin)

v3 -> v4: https://lore.kernel.org/dri-devel/[e-mail]/T/

* [5/8] Add Iago's R-b to PATCH 5/8 (Iago Toral)
* [6/8] Add Tvrtko's R-b to PATCH 6/8 (Tvrtko Ursulin)
* [7/8] Add Tvrtko's R-b to PATCH 7/8 (Tvrtko Ursulin)
* [8/8] Move `bool super_pages` to the guard (Tvrtko Ursulin)

Best Regards,
- Maíra

Maíra Canal (8):
  drm/v3d: Fix return if scheduler initialization fails
  drm/gem: Create a drm_gem_object_init_with_mnt() function
  drm/v3d: Introduce gemfs
  drm/gem: Create shmem GEM object in a given mountpoint
  drm/v3d: Reduce the alignment of the node allocation
  drm/v3d: Support Big/Super Pages when writing out PTEs
  drm/v3d: Use gemfs/THP in BO creation if available
  drm/v3d: Add modparam for turning off Big/Super Pages

 drivers/gpu/drm/drm_gem.c              | 34 +++++++++++++++--
 drivers/gpu/drm/drm_gem_shmem_helper.c | 30 +++++++++++++--
 drivers/gpu/drm/v3d/Makefile           |  3 +-
 drivers/gpu/drm/v3d/v3d_bo.c           | 21 ++++++++++-
 drivers/gpu/drm/v3d/v3d_drv.c          |  7 ++++
 drivers/gpu/drm/v3d/v3d_drv.h          | 12 +++++-
 drivers/gpu/drm/v3d/v3d_gem.c          |  6 ++-
 drivers/gpu/drm/v3d/v3d_gemfs.c        | 51 +++++++++++++++++++++++++
 drivers/gpu/drm/v3d/v3d_mmu.c          | 52 +++++++++++++++++++-------
 include/drm/drm_gem.h                  |  3 ++
 include/drm/drm_gem_shmem_helper.h     |  3 ++
 11 files changed, 195 insertions(+), 27 deletions(-)
 create mode 100644 drivers/gpu/drm/v3d/v3d_gemfs.c