On 06/05/2026 11:45, Nicolas Frattaroli wrote:
RAM is not, in fact, cheap. Especially on embedded systems with a low amount of memory, but known and well-defined userspace, more explicit resource management can lead to better utilisation patterns. As an example, a resource manager process on a purpose-built device may wish to launch, and then explicitly swap out, memory of processes that are kept "warm", to improve perceived startup latency of individual full-screen applications without making the kernel figure out the usage pattern from observation alone in order to swap out the right pages.
Have you considered memory control groups (memcg) for this purpose? Imposing a lower limit than currently allocated should trigger reclaim, so 'background' applications could have the limit lowered and then restored when moved to the foreground.
To allow for this explicit control in the context of panthor's GPU memory, add two new sysfs knobs. The first, mem_reclaim, runs an explicit priv BO reclaim cycle on the TGID written to it.
The second, mem_claim, does the opposite: it swaps BOs back into active memory.
How necessary is this mem_claim for performance? Have you done any benchmarking of explicitly claiming vs just allowing it to happen naturally? My gut feeling is that mem_claim should be unnecessary in most situations, but I'm prepared to be proved wrong.
I'm not saying this series is necessarily the wrong approach - but I think we need a bit more justification for adding a new API for this.
Thanks, Steve
Signed-off-by: Nicolas Frattaroli nicolas.frattaroli@collabora.com
Nicolas Frattaroli (4): drm/panthor: Add freed_sz parameter to reclaim_priv_bos MAINTAINERS: Add sysfs ABI docs to list of panthor files drm/panthor: Add explicit memory reclaim sysfs knob drm/panthor: Add explicit memory claim sysfs knob
Documentation/ABI/testing/sysfs-driver-panthor-mem | 34 ++++++++ MAINTAINERS | 1 + drivers/gpu/drm/panthor/panthor_drv.c | 93 ++++++++++++++++++++++ drivers/gpu/drm/panthor/panthor_gem.c | 7 +- drivers/gpu/drm/panthor/panthor_gem.h | 1 + drivers/gpu/drm/panthor/panthor_mmu.c | 70 +++++++++++++++- drivers/gpu/drm/panthor/panthor_mmu.h | 4 + 7 files changed, 205 insertions(+), 5 deletions(-)
base-commit: 2c4b906cd135bbb44855287d0d0eff0ee0b47afe change-id: 20260506-panthor-explicit-reclaim-3dffed028d8c
Best regards,
Nicolas Frattaroli nicolas.frattaroli@collabora.com