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 <[email protected]> > --- > 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 <[email protected]> >
