sched_ext: Rename scx_bpf_dispatch[_vtime]() to scx_bpf_dsq_insert[_vtime]()

In sched_ext API, a repeatedly reported pain point is the overuse of the
verb "dispatch" and confusion around "consume":

- ops.dispatch()
- scx_bpf_dispatch[_vtime]()
- scx_bpf_consume()
- scx_bpf_dispatch[_vtime]_from_dsq*()

This overloading of the term is historical. Originally, there were only
built-in DSQs and moving a task into a DSQ always dispatched it for
execution. Using the verb "dispatch" for the kfuncs to move tasks into these
DSQs made sense.

Later, user DSQs were added and scx_bpf_dispatch[_vtime]() updated to be
able to insert tasks into any DSQ. The only allowed DSQ to DSQ transfer was
from a non-local DSQ to a local DSQ and this operation was named "consume".
This was already confusing as a task could be dispatched to a user DSQ from
ops.enqueue() and then the DSQ would have to be consumed in ops.dispatch().
Later addition of scx_bpf_dispatch_from_dsq*() made the confusion even worse
as "dispatch" in this context meant moving a task to an arbitrary DSQ from a
user DSQ.

Clean up the API with the following renames:

1. scx_bpf_dispatch[_vtime]()		-> scx_bpf_dsq_insert[_vtime]()
2. scx_bpf_consume()			-> scx_bpf_dsq_move_to_local()
3. scx_bpf_dispatch[_vtime]_from_dsq*()	-> scx_bpf_dsq_move[_vtime]*()

This patch performs the first set of renames. Compatibility is maintained
by:

- The previous kfunc names are still provided by the kernel so that old
  binaries can run. Kernel generates a warning when the old names are used.

- compat.bpf.h provides wrappers for the new names which automatically fall
  back to the old names when running on older kernels. They also trigger
  build error if old names are used for new builds.

The compat features will be dropped after v6.15.

v2: Documentation updates.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Andrea Righi <arighi@nvidia.com>
Acked-by: Changwoo Min <changwoo@igalia.com>
Acked-by: Johannes Bechberger <me@mostlynerdless.de>
Acked-by: Giovanni Gherdovich <ggherdovich@suse.com>
Cc: Dan Schatzberg <dschatzberg@meta.com>
Cc: Ming Yang <yougmark94@gmail.com>

1 files changed, 7 insertions, 7 deletions

diff --git a/tools/sched_ext/scx_simple.bpf.c b/tools/sched_ext/scx_simple.bpf.c
index ed7e8d535fc5..ce86a4a690b5 100644
--- a/tools/sched_ext/scx_simple.bpf.c
+++ b/tools/sched_ext/scx_simple.bpf.c
@@ -31,10 +31,10 @@ UEI_DEFINE(uei);
 
 /*
  * Built-in DSQs such as SCX_DSQ_GLOBAL cannot be used as priority queues
- * (meaning, cannot be dispatched to with scx_bpf_dispatch_vtime()). We
+ * (meaning, cannot be dispatched to with scx_bpf_dsq_insert_vtime()). We
  * therefore create a separate DSQ with ID 0 that we dispatch to and consume
- * from. If scx_simple only supported global FIFO scheduling, then we could
- * just use SCX_DSQ_GLOBAL.
+ * from. If scx_simple only supported global FIFO scheduling, then we could just
+ * use SCX_DSQ_GLOBAL.
  */
 #define SHARED_DSQ 0
 
@@ -65,7 +65,7 @@ s32 BPF_STRUCT_OPS(simple_select_cpu, struct task_struct *p, s32 prev_cpu, u64 w
 	cpu = scx_bpf_select_cpu_dfl(p, prev_cpu, wake_flags, &is_idle);
 	if (is_idle) {
 		stat_inc(0);	/* count local queueing */
-		scx_bpf_dispatch(p, SCX_DSQ_LOCAL, SCX_SLICE_DFL, 0);
+		scx_bpf_dsq_insert(p, SCX_DSQ_LOCAL, SCX_SLICE_DFL, 0);
 	}
 
 	return cpu;
@@ -76,7 +76,7 @@ void BPF_STRUCT_OPS(simple_enqueue, struct task_struct *p, u64 enq_flags)
 	stat_inc(1);	/* count global queueing */
 
 	if (fifo_sched) {
-		scx_bpf_dispatch(p, SHARED_DSQ, SCX_SLICE_DFL, enq_flags);
+		scx_bpf_dsq_insert(p, SHARED_DSQ, SCX_SLICE_DFL, enq_flags);
 	} else {
 		u64 vtime = p->scx.dsq_vtime;
 
@@ -87,8 +87,8 @@ void BPF_STRUCT_OPS(simple_enqueue, struct task_struct *p, u64 enq_flags)
 		if (vtime_before(vtime, vtime_now - SCX_SLICE_DFL))
 			vtime = vtime_now - SCX_SLICE_DFL;
 
-		scx_bpf_dispatch_vtime(p, SHARED_DSQ, SCX_SLICE_DFL, vtime,
-				       enq_flags);
+		scx_bpf_dsq_insert_vtime(p, SHARED_DSQ, SCX_SLICE_DFL, vtime,
+					 enq_flags);
 	}
 }