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Diffstat (limited to 'Documentation/scheduler/sched-ext.rst')
| -rw-r--r-- | Documentation/scheduler/sched-ext.rst | 30 |
1 files changed, 27 insertions, 3 deletions
diff --git a/Documentation/scheduler/sched-ext.rst b/Documentation/scheduler/sched-ext.rst index 9e2882d937b4..d74c2c2b9ef3 100644 --- a/Documentation/scheduler/sched-ext.rst +++ b/Documentation/scheduler/sched-ext.rst @@ -43,7 +43,6 @@ options should be enabled to use sched_ext: CONFIG_DEBUG_INFO_BTF=y CONFIG_BPF_JIT_ALWAYS_ON=y CONFIG_BPF_JIT_DEFAULT_ON=y - CONFIG_PAHOLE_HAS_BTF_TAG=y sched_ext is used only when the BPF scheduler is loaded and running. @@ -58,7 +57,8 @@ in ``ops->flags``, all ``SCHED_NORMAL``, ``SCHED_BATCH``, ``SCHED_IDLE``, and However, when the BPF scheduler is loaded and ``SCX_OPS_SWITCH_PARTIAL`` is set in ``ops->flags``, only tasks with the ``SCHED_EXT`` policy are scheduled by sched_ext, while tasks with ``SCHED_NORMAL``, ``SCHED_BATCH`` and -``SCHED_IDLE`` policies are scheduled by the fair-class scheduler. +``SCHED_IDLE`` policies are scheduled by the fair-class scheduler which has +higher sched_class precedence than ``SCHED_EXT``. Terminating the sched_ext scheduler program, triggering `SysRq-S`, or detection of any internal error including stalled runnable tasks aborts the @@ -345,6 +345,8 @@ Where to Look The functions prefixed with ``scx_bpf_`` can be called from the BPF scheduler. +* ``kernel/sched/ext_idle.c`` contains the built-in idle CPU selection policy. + * ``tools/sched_ext/`` hosts example BPF scheduler implementations. * ``scx_simple[.bpf].c``: Minimal global FIFO scheduler example using a @@ -353,13 +355,35 @@ Where to Look * ``scx_qmap[.bpf].c``: A multi-level FIFO scheduler supporting five levels of priority implemented with ``BPF_MAP_TYPE_QUEUE``. + * ``scx_central[.bpf].c``: A central FIFO scheduler where all scheduling + decisions are made on one CPU, demonstrating ``LOCAL_ON`` dispatching, + tickless operation, and kthread preemption. + + * ``scx_cpu0[.bpf].c``: A scheduler that queues all tasks to a shared DSQ + and only dispatches them on CPU0 in FIFO order. Useful for testing bypass + behavior. + + * ``scx_flatcg[.bpf].c``: A flattened cgroup hierarchy scheduler + implementing hierarchical weight-based cgroup CPU control by compounding + each cgroup's share at every level into a single flat scheduling layer. + + * ``scx_pair[.bpf].c``: A core-scheduling example that always makes + sibling CPU pairs execute tasks from the same CPU cgroup. + + * ``scx_sdt[.bpf].c``: A variation of ``scx_simple`` demonstrating BPF + arena memory management for per-task data. + + * ``scx_userland[.bpf].c``: A minimal scheduler demonstrating user space + scheduling. Tasks with CPU affinity are direct-dispatched in FIFO order; + all others are scheduled in user space by a simple vruntime scheduler. + ABI Instability =============== The APIs provided by sched_ext to BPF schedulers programs have no stability guarantees. This includes the ops table callbacks and constants defined in ``include/linux/sched/ext.h``, as well as the ``scx_bpf_`` kfuncs defined in -``kernel/sched/ext.c``. +``kernel/sched/ext.c`` and ``kernel/sched/ext_idle.c``. While we will attempt to provide a relatively stable API surface when possible, they are subject to change without warning between kernel |