Commit 0f0714a3 authored by Andrea Righi's avatar Andrea Righi Committed by Tejun Heo
Browse files

sched_ext: Documentation: add task lifecycle summary 



Understanding the lifecycle of a task in sched_ext can be not trivial,
therefore add a section to the main documentation that summarizes the
entire workflow of a task using pseudo-code.

Signed-off-by: default avatarAndrea Righi <arighi@nvidia.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent b214b04d

Documentation/scheduler/sched-ext.rst

+36 −0
Original line number Diff line number Diff line
@@ -294,6 +294,42 @@ dispatching, and must be dispatched to with ``scx_bpf_dsq_insert()``. See 
the function documentation and usage in ``tools/sched_ext/scx_simple.bpf.c``

for more information.



Task Lifecycle

--------------



The following pseudo-code summarizes the entire lifecycle of a task managed

by a sched_ext scheduler:



.. code-block:: c



    ops.init_task();            /* A new task is created */

    ops.enable();               /* Enable BPF scheduling for the task */



    while (task in SCHED_EXT) {

        if (task can migrate)

            ops.select_cpu();   /* Called on wakeup (optimization) */



        ops.runnable();         /* Task becomes ready to run */



        while (task is runnable) {

            if (task is not in a DSQ) {

                ops.enqueue();  /* Task can be added to a DSQ */



                /* A CPU becomes available */



                ops.dispatch(); /* Task is moved to a local DSQ */

            }

            ops.running();      /* Task starts running on its assigned CPU */

            ops.tick();         /* Called every 1/HZ seconds */

            ops.stopping();     /* Task stops running (time slice expires or wait) */

        }



        ops.quiescent();        /* Task releases its assigned CPU (wait) */

    }



    ops.disable();              /* Disable BPF scheduling for the task */

    ops.exit_task();            /* Task is destroyed */



Where to Look

=============