Commit 6f34d8d3 authored by Tejun Heo's avatar Tejun Heo
Browse files

sched_ext: Use shorter slice while bypassing 



While bypassing, tasks are scheduled in FIFO order which favors tasks that
hog CPUs. This can slow down e.g. unloading of the BPF scheduler. While
bypassing, guaranteeing timely forward progress is the main goal. There's no
point in giving long slices. Shorten the time slice used while bypassing
from 20ms to 5ms.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarDavid Vernet <void@manifault.com>
parent b7b3b2db

kernel/sched/ext.c

+4 −2
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ 
#define SCX_OP_IDX(op)		(offsetof(struct sched_ext_ops, op) / sizeof(void (*)(void)))



enum scx_consts {

	SCX_SLICE_BYPASS		= SCX_SLICE_DFL / 4,

	SCX_DSP_DFL_MAX_BATCH		= 32,

	SCX_DSP_MAX_LOOPS		= 32,

	SCX_WATCHDOG_MAX_TIMEOUT	= 30 * HZ,
@@ -1944,6 +1945,7 @@ static bool scx_rq_online(struct rq *rq) 
static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags,

			    int sticky_cpu)

{

	bool bypassing = scx_rq_bypassing(rq);

	struct task_struct **ddsp_taskp;

	unsigned long qseq;
@@ -1961,7 +1963,7 @@ static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags, 
	if (!scx_rq_online(rq))

		goto local;



	if (scx_rq_bypassing(rq))

	if (bypassing)

		goto global;



	if (p->scx.ddsp_dsq_id != SCX_DSQ_INVALID)
@@ -2016,7 +2018,7 @@ static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags, 


global:

	touch_core_sched(rq, p);	/* see the comment in local: */

	p->scx.slice = SCX_SLICE_DFL;

	p->scx.slice = bypassing ? SCX_SLICE_BYPASS : SCX_SLICE_DFL;

	dispatch_enqueue(find_global_dsq(p), p, enq_flags);

}