+Chia-I On Fri, 9 Jan 2026 14:07:52 +0100 Boris Brezillon <[email protected]> wrote:
> Hello, > > This is an attempt at adding a GEM shrinker to panthor so the system > can finally reclaim GPU memory. > > This implementation is losely based on the MSM shrinker (which is why > I added the MSM maintainers in Cc), and it's relying on the drm_gpuvm > eviction/validation infrastructure. > > I've only done very basic IGT-based [1] and chromium-based (opening > a lot of tabs on Aquarium until the system starts reclaiming+swaping > out GPU buffers) testing, but I'm posting this early so I can get > preliminary feedback on the implementation. If someone knows about > better tools/ways to test the shrinker, please let me know. > > A few words about some design/implementation choices: > - No MADVISE support because I want to see if we can live with just > transparent reclaim > - We considered basing this implementation on the generic shrinker work > started by Dmitry [2], but > 1. with the activeness/idleness tracking happening at the VM > granularity, having per-BO LRUs would caused a lot of > list_move()s that are not really needed (the VM as a whole > become active/idle, we can track individual BOs) > 2. Thomas Zimmermann recently suggested that we should have our > own GEM implementation instead of trying to add this extra reclaim > complexity to gem-shmem. There are some plans to create a > gem-uma (Unified Memory Architecture) lib that would do more > than gem-shmem but in a way that doesn't force all its users > to pay the overhead (size overhead of the gem object, mostly) > for features they don't use. Patch "Part ways with > drm_gem_shmem_object" is showing what this component-based lib > API could look like if it were to be extracted > - At the moment we only support swapout, but we could add an > extra flag to specify when buffer content doesn't need to be > preserved to avoid the swapout/swapin dance. First candidate for > this DISCARD_ON_RECLAIM flag would probably be the tiler heap chunks. > - Reclaim uses _try_lock() all the way because of the various lock order > inversions between the reclaim path and submission paths. That means > we don't try very hard to reclaim hot GPU buffers, but the locking is > such a mess that I don't really see a better option to be honest. > > Regards, > > Boris > > [1]https://gitlab.freedesktop.org/bbrezillon/igt-gpu-tools/-/commit/fc76934a5579767d2aabe787d40e38a17c3f4ea4 > [2]https://lkml.org/lkml/2024/1/5/665 > > Akash Goel (1): > drm/panthor: Add a GEM shrinker > > Boris Brezillon (8): > drm/gem: Consider GEM object reclaimable if shrinking fails > drm/gpuvm: Validate BOs in the extobj list when VM is resv protected > drm/panthor: Move panthor_gems_debugfs_init() to panthor_gem.c > drm/panthor: Group panthor_kernel_bo_xxx() helpers > drm/panthor: Part ways with drm_gem_shmem_object > drm/panthor: Lazily allocate pages on mmap() > drm/panthor: Split panthor_vm_prepare_map_op_ctx() to prepare for > reclaim > drm/panthor: Track the number of mmap on a BO > > drivers/gpu/drm/drm_gem.c | 10 + > drivers/gpu/drm/drm_gpuvm.c | 23 +- > drivers/gpu/drm/panthor/Kconfig | 1 - > drivers/gpu/drm/panthor/panthor_device.c | 11 +- > drivers/gpu/drm/panthor/panthor_device.h | 73 ++ > drivers/gpu/drm/panthor/panthor_drv.c | 33 +- > drivers/gpu/drm/panthor/panthor_fw.c | 16 +- > drivers/gpu/drm/panthor/panthor_gem.c | 1387 ++++++++++++++++++---- > drivers/gpu/drm/panthor/panthor_gem.h | 135 ++- > drivers/gpu/drm/panthor/panthor_mmu.c | 451 +++++-- > drivers/gpu/drm/panthor/panthor_mmu.h | 8 + > drivers/gpu/drm/panthor/panthor_sched.c | 9 +- > include/drm/drm_gpuvm.h | 6 + > 13 files changed, 1829 insertions(+), 334 deletions(-) >
