KFunc scx_bpf_dsq_insert
This function inserts a task into the First In First Out(FIFO) queue of a Dispatch Queue(DSQ)
Definition
Insert p into the FIFO queue of the DSQ identified by dsq_id. It is safe to call this function spuriously. Can be called from ops.enqueue(), ops.select_cpu(), and ops.dispatch().
When called from ops.select_cpu() or ops.enqueue(), it's for direct dispatch and p must match the task being enqueued.
When called from ops.select_cpu(), enq_flags and dsp_id are stored, and p will be directly inserted into the corresponding dispatch queue after ops.select_cpu() returns. If p is inserted into SCX_DSQ_LOCAL, it will be inserted into the local DSQ of the CPU returned by ops.select_cpu(). enq_flags are OR'd with the enqueue flags on the enqueue path before the task is inserted.
When called from ops.dispatch(), there are no restrictions on p or dsq_id and this function can be called up to ops.dispatch_max_batch times to insert multiple tasks. scx_bpf_dispatch_nr_slots returns the number of the remaining slots. scx_bpf_consume flushes the batch and resets the counter.
This function doesn't have any locking restrictions and may be called under BPF locks (in the future when BPF introduces more flexible locking).
p is allowed to run for slice. The scheduling path is triggered on slice exhaustion. If zero, the current residual slice is maintained. If SCX_SLICE_INF, p never expires and the BPF scheduler must kick the CPU with scx_bpf_kick_cpu to trigger scheduling.
Parameters
p: task_struct to insert
dsq_id: DSQ to insert into
slice: duration p can run for in nanoseconds, 0 to keep the current value
enq_flags: SCX_ENQ_*
Flags
SCX_ENQ_WAKEUP: Task just became runnable
SCX_ENQ_HEAD: Place at front of queue (tail if not specified)
SCX_ENQ_CPU_SELECTED: ->select_task_rq() was called
SCX_ENQ_PREEMPT: Set the following to trigger preemption when calling scx_bpf_dsq_insert with a local dsq as the target. The slice of the current task is cleared to zero and the CPU is kicked into the scheduling path. Implies SCX_ENQ_HEAD.
SCX_ENQ_REENQ: The task being enqueued was previously enqueued on the current CPU's SCX_DSQ_LOCAL, but was removed from it in a call to the scx_bpf_reenqueue_local kfunc. If scx_bpf_reenqueue_local was invoked in a ->cpu_release() callback, and the task is again dispatched back to SCX_LOCAL_DSQ by this current ->enqueue(), the task will not be scheduled on the CPU until at least the next invocation of the ->cpu_acquire() callback.
SCX_ENQ_LAST: The task being enqueued is the only task available for the cpu. By default, ext core keeps executing such tasks but when SCX_OPS_ENQ_LAST is specified, they are ops.enqueue()'d with the SCX_ENQ_LAST flag set. The BPF scheduler is responsible for triggering a follow-up scheduling event. Otherwise, Execution may stall.
Signature
void scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id, u64 slice, u64 enq_flags)
Usage
Docs could be improved
This part of the docs is incomplete, contributions are very welcome
Program types
The following program types can make use of this kfunc:
Example
Docs could be improved
This part of the docs is incomplete, contributions are very welcome