On 08/10/2025 13:35, Christian König wrote:
On 08.10.25 13:53, Tvrtko Ursulin wrote:
Disclaimer:
Please note that as this series includes a patch which touches a good number of
drivers I will only copy everyone in the cover letter and the respective patch.
Assumption is people are subscribed to dri-devel so can look at the whole series
there. I know someone is bound to complain for both the case when everyone is
copied on everything for getting too much email, and also for this other case.
So please be flexible.
Description:
All drivers which use the TTM pool allocator end up requesting large order
allocations when allocating large buffers. Those can be slow due memory pressure
and so add latency to buffer creation. But there is often also a size limit
above which contiguous blocks do not bring any performance benefits. This series
allows drivers to say when it is okay for the TTM to try a bit less hard.
We do this by allowing drivers to specify this cut off point when creating the
TTM device and pools. Allocations above this size will skip direct reclaim so
under memory pressure worst case latency will improve. Background reclaim is
still kicked off and both before and after the memory pressure all the TTM pool
buckets remain to be used as they are today.
This is especially interesting if someone has configured MAX_PAGE_ORDER to
higher than the default. And even with the default, with amdgpu for example,
the last patch in the series makes use of the new feature by telling TTM that
above 2MiB we do not expect performance benefits. Which makes TTM not try direct
reclaim for the top bucket (4MiB).
End result is TTM drivers become a tiny bit nicer mm citizens and users benefit
from better worst case buffer creation latencies. As a side benefit we get rid
of two instances of those often very unreadable mutliple nameless booleans
function signatures.
If this sounds interesting and gets merge the invidual drivers can follow up
with patches configuring their thresholds.
v2:
* Christian suggested to pass in the new data by changing the function
signatures.
v3:
* Moved ttm pool helpers into new ttm_pool_internal.h. (Christian)
Patch #3 is Acked-by: Christian König <[email protected]>.
The rest is Reviewed-by: Christian König <[email protected]>
Thank you!
So I think now I need acks to merge via drm-misc for all the drivers
which have their own trees. Which seems to be just xe.
Also interesting for other drivers is that when this lands folks can
start passing in their "max size which leads to performance gains" via
TTM_POOL_BENEFICIAL_ORDER and get the worst case allocation latency
improvements.
I am thinking xe also maxes out at 2MiB pages, for others I don't know.
Regards,
Tvrtko
v1 thread:
https://lore.kernel.org/dri-devel/[email protected]/
Cc: Alex Deucher <[email protected]>
Cc: Christian König <[email protected]>
Cc: Danilo Krummrich <[email protected]>
Cc: Dave Airlie <[email protected]>
Cc: Gerd Hoffmann <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: Lucas De Marchi <[email protected]>
Cc: Lyude Paul <[email protected]>
Cc: Maarten Lankhorst <[email protected]>
Cc: Maxime Ripard <[email protected]>
Cc: Rodrigo Vivi <[email protected]>
Cc: Sui Jingfeng <[email protected]>
Cc: Thadeu Lima de Souza Cascardo <[email protected]>
Cc: Thomas Hellström <[email protected]>
Cc: Thomas Zimmermann <[email protected]>
Cc: Zack Rusin <[email protected]>
Tvrtko Ursulin (5):
drm/ttm: Add getter for some pool properties
drm/ttm: Replace multiple booleans with flags in pool init
drm/ttm: Replace multiple booleans with flags in device init
drm/ttm: Allow drivers to specify maximum beneficial TTM pool size
drm/amdgpu: Configure max beneficial TTM pool allocation order
drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 7 +--
drivers/gpu/drm/drm_gem_vram_helper.c | 2 +-
drivers/gpu/drm/i915/intel_region_ttm.c | 2 +-
drivers/gpu/drm/loongson/lsdc_ttm.c | 2 +-
drivers/gpu/drm/nouveau/nouveau_ttm.c | 4 +-
drivers/gpu/drm/qxl/qxl_ttm.c | 2 +-
drivers/gpu/drm/radeon/radeon_ttm.c | 4 +-
drivers/gpu/drm/ttm/tests/ttm_bo_test.c | 16 +++----
.../gpu/drm/ttm/tests/ttm_bo_validate_test.c | 2 +-
drivers/gpu/drm/ttm/tests/ttm_device_test.c | 31 +++++--------
drivers/gpu/drm/ttm/tests/ttm_kunit_helpers.c | 22 ++++-----
drivers/gpu/drm/ttm/tests/ttm_kunit_helpers.h | 7 +--
drivers/gpu/drm/ttm/tests/ttm_pool_test.c | 23 +++++-----
drivers/gpu/drm/ttm/ttm_device.c | 7 ++-
drivers/gpu/drm/ttm/ttm_pool.c | 45 +++++++++++--------
drivers/gpu/drm/ttm/ttm_pool_internal.h | 24 ++++++++++
drivers/gpu/drm/ttm/ttm_tt.c | 10 +++--
drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 4 +-
drivers/gpu/drm/xe/xe_device.c | 2 +-
include/drm/ttm/ttm_device.h | 2 +-
include/drm/ttm/ttm_pool.h | 13 +++---
21 files changed, 125 insertions(+), 106 deletions(-)
create mode 100644 drivers/gpu/drm/ttm/ttm_pool_internal.h
