kernel/linux.git/include/linux/cgroup_dmem.h, branch v7.3-rc1

cgroup/dmem: Add reclaim callback for lowering max below current usage

2026-08-06T21:38:03+00:00

Add an optional reclaim callback to struct dmem_cgroup_region. When dmem.max is set below the current usage of a cgroup pool, the new limit is applied immediately (so that concurrent allocations are throttled while reclaim is in progress) and then the driver is asked to evict memory to bring usage back below the limit. Reclaim is attempted up to a bounded number of times. No error is returned to userspace if usage remains above the limit after reclaim, and a pending signal will abort the reclaim loop early. This matches the behavior of memory.max in the memory cgroup controller. Also honor O_NONBLOCK so that if that flag is set during the max value write, no reclaim is initiated. The idea is to avoid charging the reclaim cost to the writer of the max value. v2: - Write max before reclaim is attempted (Maarten) - Let signals abort the reclaim without error (Maarten) - If a new max value is written with the O_NONBLOCK flag, reclaim is not attempted (Maarten) - Extract region from the pool parameter rather than passing it explicitly to set_resource_xxx(). v3: - Use an rw_semaphore (unregister_sem) to protect reclaim callbacks against concurrent region unregistration: readers (reclaim) hold the read side; dmem_cgroup_unregister_region() takes the write side to drain in-flight callbacks before returning. (Sashiko-bot) v5: - Rebased on the introduction of struct dmem_cgroup_init. - Use nonblock=true in reset_all_resource_limits() to avoid sleeping inside rcu_read_lock() in dmemcs_offline(). (Sashiko-bot) - Compare usage against the truncated limit value stored in cnt.max, not the original u64. (Sashiko-bot) - Use a DMEM_MAX_RECLAIM_RETRIES (16) retry budget instead of 5, matching the memcg controller's MAX_RECLAIM_RETRIES. Only -ENOSPC (no progress) counts against the retry budget; other errors terminate the loop immediately. v6: - Fix dmem_cgroup_ops->reclaim docstring: -ENOSPC does not stop reclaim immediately but is retried up to DMEM_MAX_RECLAIM_RETRIES times; only other negative errors terminate the loop. (Sashiko-bot) v7: - Replace the per-region rw_semaphore with a static SRCU domain (dmemcg_srcu). SRCU is a better fit than rwsem for this use: it avoids the per-region lock overhead on every reclaim call, and synchronize_srcu() at unregister time is a rare operation. (Maarten) - Trim in-function comments to focus on what rather than how. Assisted-by: GitHub_Copilot:claude-sonnet-4.6 Signed-off-by: Thomas Hellström Reviewed-by: Maarten Lankhorst Tested-by: Thadeu Lima de Souza Cascardo Link: https://patch.msgid.link/20260725100036.2372-4-thomas.hellstrom@linux.intel.com Signed-off-by: Maarten Lankhorst

cgroup/dmem: Introduce struct dmem_cgroup_init for region initialization

2026-08-06T21:37:56+00:00

Replace the bare u64 size argument to dmem_cgroup_register_region() and drmm_cgroup_register_region() with a const struct dmem_cgroup_init * pointer. The struct currently carries only the size field, but using a struct makes the API extensible: future callers can supply additional initialization parameters without adding more positional arguments. Update all in-tree callers (amdgpu, xe) to use a compound-literal initializer. v5: - Commit introduced. Assisted-by: GitHub_Copilot:claude-sonnet-4.6 Signed-off-by: Thomas Hellström Reviewed-by: Maarten Lankhorst Tested-by: Thadeu Lima de Souza Cascardo Link: https://patch.msgid.link/20260725100036.2372-3-thomas.hellstrom@linux.intel.com Acked-by: Dave Airlie Acked-by: Christian König Signed-off-by: Maarten Lankhorst

cgroup,cgroup/dmem: Add (dmem_)cgroup_common_ancestor helper

2026-08-05T08:34:42+00:00

This helps to find a common subtree of two resources, which is important when determining whether it's helpful to evict one resource in favor of another. To facilitate this, add a common helper to find the ancestor of two cgroups using each cgroup's ancestor array. Tested-by: Thadeu Lima de Souza Cascardo Reviewed-by: Maarten Lankhorst Reviewed-by: Timur Kristóf Signed-off-by: Natalie Vock Link: https://patch.msgid.link/20260804-dmemcg-aggressive-protect-v8-2-07af96681bf8@gmx.de

cgroup/dmem: Add queries for protection values

2026-08-05T08:33:32+00:00

Callers can use this feedback to be more aggressive in making space for allocations of a cgroup if they know it is protected. These are counterparts to memcg's mem_cgroup_below_{min,low}. Reviewed-by: Maarten Lankhorst Reviewed-by: Timur Kristóf Signed-off-by: Natalie Vock Link: https://patch.msgid.link/20260804-dmemcg-aggressive-protect-v8-1-07af96681bf8@gmx.de

kernel/cgroup: Add "dmem" memory accounting cgroup

2025-01-06T16:24:38+00:00

This code is based on the RDMA and misc cgroup initially, but now uses page_counter. It uses the same min/low/max semantics as the memory cgroup as a result. There's a small mismatch as TTM uses u64, and page_counter long pages. In practice it's not a problem. 32-bits systems don't really come with >=4GB cards and as long as we're consistently wrong with units, it's fine. The device page size may not be in the same units as kernel page size, and each region might also have a different page size (VRAM vs GART for example). The interface is simple: - Call dmem_cgroup_register_region() - Use dmem_cgroup_try_charge to check if you can allocate a chunk of memory, use dmem_cgroup__uncharge when freeing it. This may return an error code, or -EAGAIN when the cgroup limit is reached. In that case a reference to the limiting pool is returned. - The limiting cs can be used as compare function for dmem_cgroup_state_evict_valuable. - After having evicted enough, drop reference to limiting cs with dmem_cgroup_pool_state_put. This API allows you to limit device resources with cgroups. You can see the supported cards in /sys/fs/cgroup/dmem.capacity You need to echo +dmem to cgroup.subtree_control, and then you can partition device memory. Co-developed-by: Friedrich Vock Signed-off-by: Friedrich Vock Co-developed-by: Maxime Ripard Signed-off-by: Maarten Lankhorst Acked-by: Tejun Heo Link: https://lore.kernel.org/r/20241204143112.1250983-1-dev@lankhorst.se Signed-off-by: Maxime Ripard