kernel/git/stable/linux-stable.git/tools/sched_ext, branch linux-6.15.y

sched_ext: Mark SCX_OPS_HAS_CGROUP_WEIGHT for deprecation

2025-04-08T18:53:52+00:00

SCX_OPS_HAS_CGROUP_WEIGHT was only used to suppress the missing cgroup weight support warnings. Now that the warnings are removed, the flag doesn't do anything. Mark it for deprecation and remove its usage from scx_flatcg. v2: Actually include the scx_flatcg update. Signed-off-by: Tejun Heo Suggested-and-reviewed-by: Andrea Righi

tools/sched_ext: Sync with scx repo

2025-04-02T19:08:33+00:00

Synchronize with https://github.com/sched-ext/scx at dc44584874f0 ("kernel: Synchronize with kernel tools/sched_ext"). - READ/WRITE_ONCE() is made more proper and READA_ONCE_ARENA() is dropped. - scale_by_task_weight[_inverse]() helpers added. - Enum defs expanded to cover more and new enums. - Don't trigger fatal error when some enums are missing from kernel BTF. Signed-off-by: Tejun Heo

sched_ext: Change the event type from u64 to s64

2025-03-04T18:05:23+00:00

The event count could be negative in the future, so change the event type from u64 to s64. Signed-off-by: Changwoo Min Signed-off-by: Tejun Heo

sched_ext: Merge branch 'for-6.14-fixes' into for-6.15

2025-03-03T18:02:22+00:00

Pull for-6.14-fixes to receive: 9360dfe4cbd6 ("sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl()") which conflicts with: 337d1b354a29 ("sched_ext: Move built-in idle CPU selection policy to a separate file") Signed-off-by: Tejun Heo

tools/sched_ext: Provide a compatible helper for scx_bpf_events()

2025-02-27T16:26:58+00:00

Introduce __COMPAT_scx_bpf_events() to use scx_bpf_events() in a compatible way also with kernels that don't provide this kfunc. This also fixes the following error with scx_qmap when running on a kernel that does not provide scx_bpf_events(): ; scx_bpf_events(&events, sizeof(events)); @ scx_qmap.bpf.c:777 318: (b7) r2 = 72 ; R2_w=72 async_cb 319: kfunc 'scx_bpf_events' is referenced but wasn't resolved Fixes: 9865f31d852a4 ("sched_ext: Add scx_bpf_events() and scx_read_event() for BPF schedulers") Signed-off-by: Andrea Righi Signed-off-by: Tejun Heo

tools/sched_ext: Provide consistent access to scx flags

2025-02-25T18:36:36+00:00

Make all the SCX_OPS_* and SCX_PICK_IDLE_* flags available to the user-space part of the schedulers via the compat interface. This allows schedulers / selftests to set all the ops flags in user-space, rather than having them split between BPF and user-space. Signed-off-by: Andrea Righi Acked-by: Changwoo Min Signed-off-by: Tejun Heo

sched_ext: idle: Introduce scx_bpf_nr_node_ids()

2025-02-24T17:37:42+00:00

Similarly to scx_bpf_nr_cpu_ids(), introduce a new kfunc scx_bpf_nr_node_ids() to expose the maximum number of NUMA nodes in the system. BPF schedulers can use this information together with the new node-aware kfuncs, for example to create per-node DSQs, validate node IDs, etc. Signed-off-by: Andrea Righi Signed-off-by: Tejun Heo

sched_ext: idle: Introduce node-aware idle cpu kfunc helpers

2025-02-18T19:10:24+00:00

Introduce a new kfunc to retrieve the node associated to a CPU: int scx_bpf_cpu_node(s32 cpu) Add the following kfuncs to provide BPF schedulers direct access to per-node idle cpumasks information: const struct cpumask *scx_bpf_get_idle_cpumask_node(int node) const struct cpumask *scx_bpf_get_idle_smtmask_node(int node) s32 scx_bpf_pick_idle_cpu_node(const cpumask_t *cpus_allowed, int node, u64 flags) s32 scx_bpf_pick_any_cpu_node(const cpumask_t *cpus_allowed, int node, u64 flags) Moreover, trigger an scx error when any of the non-node aware idle CPU kfuncs are used when SCX_OPS_BUILTIN_IDLE_PER_NODE is enabled. Cc: Yury Norov [NVIDIA] Signed-off-by: Andrea Righi Reviewed-by: Yury Norov [NVIDIA] Signed-off-by: Tejun Heo

sched_ext: idle: Per-node idle cpumasks

2025-02-16T16:52:20+00:00

Using a single global idle mask can lead to inefficiencies and a lot of stress on the cache coherency protocol on large systems with multiple NUMA nodes, since all the CPUs can create a really intense read/write activity on the single global cpumask. Therefore, split the global cpumask into multiple per-NUMA node cpumasks to improve scalability and performance on large systems. The concept is that each cpumask will track only the idle CPUs within its corresponding NUMA node, treating CPUs in other NUMA nodes as busy. In this way concurrent access to the idle cpumask will be restricted within each NUMA node. The split of multiple per-node idle cpumasks can be controlled using the SCX_OPS_BUILTIN_IDLE_PER_NODE flag. By default SCX_OPS_BUILTIN_IDLE_PER_NODE is not enabled and a global host-wide idle cpumask is used, maintaining the previous behavior. NOTE: if a scheduler explicitly enables the per-node idle cpumasks (via SCX_OPS_BUILTIN_IDLE_PER_NODE), scx_bpf_get_idle_cpu/smtmask() will trigger an scx error, since there are no system-wide cpumasks. = Test = Hardware: - System: DGX B200 - CPUs: 224 SMT threads (112 physical cores) - Processor: INTEL(R) XEON(R) PLATINUM 8570 - 2 NUMA nodes Scheduler: - scx_simple [1] (so that we can focus at the built-in idle selection policy and not at the scheduling policy itself) Test: - Run a parallel kernel build `make -j $(nproc)` and measure the average elapsed time over 10 runs: avg time | stdev ---------+------ before: 52.431s | 2.895 after: 50.342s | 2.895 = Conclusion = Splitting the global cpumask into multiple per-NUMA cpumasks helped to achieve a speedup of approximately +4% with this particular architecture and test case. The same test on a DGX-1 (40 physical cores, Intel Xeon E5-2698 v4 @ 2.20GHz, 2 NUMA nodes) shows a speedup of around 1.5-3%. On smaller systems, I haven't noticed any measurable regressions or improvements with the same test (parallel kernel build) and scheduler (scx_simple). Moreover, with a modified scx_bpfland that uses the new NUMA-aware APIs I observed an additional +2-2.5% performance improvement with the same test. [1] https://github.com/sched-ext/scx/blob/main/scheds/c/scx_simple.bpf.c Cc: Yury Norov [NVIDIA] Signed-off-by: Andrea Righi Reviewed-by: Yury Norov [NVIDIA] Signed-off-by: Tejun Heo

sched_ext: idle: Introduce SCX_OPS_BUILTIN_IDLE_PER_NODE

2025-02-16T16:52:20+00:00

Add the new scheduler flag SCX_OPS_BUILTIN_IDLE_PER_NODE, which allows BPF schedulers to select between using a global flat idle cpumask or multiple per-node cpumasks. This only introduces the flag and the mechanism to enable/disable this feature without affecting any scheduling behavior. Cc: Yury Norov [NVIDIA] Signed-off-by: Andrea Righi Reviewed-by: Yury Norov [NVIDIA] Signed-off-by: Tejun Heo