[PATCH v8 6/6] sched_ext: Use time helpers in BPF schedulers

[Changwoo Min <changwoo@igalia.com>]

Modify the BPF schedulers to use time helpers defined in common.bpf.h

Signed-off-by: Changwoo Min <changwoo@igalia.com>
---
 tools/sched_ext/scx_central.bpf.c |  7 +------
 tools/sched_ext/scx_flatcg.bpf.c  | 21 ++++++++-------------
 tools/sched_ext/scx_simple.bpf.c  |  9 ++-------
 3 files changed, 11 insertions(+), 26 deletions(-)

diff --git a/tools/sched_ext/scx_central.bpf.c b/tools/sched_ext/scx_central.bpf.c
index 4239034ad593..50bc1737c167 100644
--- a/tools/sched_ext/scx_central.bpf.c
+++ b/tools/sched_ext/scx_central.bpf.c
@@ -87,11 +87,6 @@ struct {
 	__type(value, struct central_timer);
 } central_timer SEC(".maps");
 
-static bool vtime_before(u64 a, u64 b)
-{
-	return (s64)(a - b) < 0;
-}
-
 s32 BPF_STRUCT_OPS(central_select_cpu, struct task_struct *p,
 		   s32 prev_cpu, u64 wake_flags)
 {
@@ -279,7 +274,7 @@ static int central_timerfn(void *map, int *key, struct bpf_timer *timer)
 		/* kick iff the current one exhausted its slice */
 		started_at = ARRAY_ELEM_PTR(cpu_started_at, cpu, nr_cpu_ids);
 		if (started_at && *started_at &&
-		    vtime_before(now, *started_at + slice_ns))
+		    time_before(now, *started_at + slice_ns))
 			continue;
 
 		/* and there's something pending */
diff --git a/tools/sched_ext/scx_flatcg.bpf.c b/tools/sched_ext/scx_flatcg.bpf.c
index 5f588963fb2f..2c720e3ecad5 100644
--- a/tools/sched_ext/scx_flatcg.bpf.c
+++ b/tools/sched_ext/scx_flatcg.bpf.c
@@ -137,11 +137,6 @@ static u64 div_round_up(u64 dividend, u64 divisor)
 	return (dividend + divisor - 1) / divisor;
 }
 
-static bool vtime_before(u64 a, u64 b)
-{
-	return (s64)(a - b) < 0;
-}
-
 static bool cgv_node_less(struct bpf_rb_node *a, const struct bpf_rb_node *b)
 {
 	struct cgv_node *cgc_a, *cgc_b;
@@ -271,7 +266,7 @@ static void cgrp_cap_budget(struct cgv_node *cgv_node, struct fcg_cgrp_ctx *cgc)
 	 */
 	max_budget = (cgrp_slice_ns * nr_cpus * cgc->hweight) /
 		(2 * FCG_HWEIGHT_ONE);
-	if (vtime_before(cvtime, cvtime_now - max_budget))
+	if (time_before(cvtime, cvtime_now - max_budget))
 		cvtime = cvtime_now - max_budget;
 
 	cgv_node->cvtime = cvtime;
@@ -401,7 +396,7 @@ void BPF_STRUCT_OPS(fcg_enqueue, struct task_struct *p, u64 enq_flags)
 		 * Limit the amount of budget that an idling task can accumulate
 		 * to one slice.
 		 */
-		if (vtime_before(tvtime, cgc->tvtime_now - SCX_SLICE_DFL))
+		if (time_before(tvtime, cgc->tvtime_now - SCX_SLICE_DFL))
 			tvtime = cgc->tvtime_now - SCX_SLICE_DFL;
 
 		scx_bpf_dsq_insert_vtime(p, cgrp->kn->id, SCX_SLICE_DFL,
@@ -535,7 +530,7 @@ void BPF_STRUCT_OPS(fcg_running, struct task_struct *p)
 		 * from multiple CPUs and thus racy. Any error should be
 		 * contained and temporary. Let's just live with it.
 		 */
-		if (vtime_before(cgc->tvtime_now, p->scx.dsq_vtime))
+		if (time_before(cgc->tvtime_now, p->scx.dsq_vtime))
 			cgc->tvtime_now = p->scx.dsq_vtime;
 	}
 	bpf_cgroup_release(cgrp);
@@ -645,7 +640,7 @@ static bool try_pick_next_cgroup(u64 *cgidp)
 	cgv_node = container_of(rb_node, struct cgv_node, rb_node);
 	cgid = cgv_node->cgid;
 
-	if (vtime_before(cvtime_now, cgv_node->cvtime))
+	if (time_before(cvtime_now, cgv_node->cvtime))
 		cvtime_now = cgv_node->cvtime;
 
 	/*
@@ -744,7 +739,7 @@ void BPF_STRUCT_OPS(fcg_dispatch, s32 cpu, struct task_struct *prev)
 	if (!cpuc->cur_cgid)
 		goto pick_next_cgroup;
 
-	if (vtime_before(now, cpuc->cur_at + cgrp_slice_ns)) {
+	if (time_before(now, cpuc->cur_at + cgrp_slice_ns)) {
 		if (scx_bpf_dsq_move_to_local(cpuc->cur_cgid)) {
 			stat_inc(FCG_STAT_CNS_KEEP);
 			return;
@@ -920,14 +915,14 @@ void BPF_STRUCT_OPS(fcg_cgroup_move, struct task_struct *p,
 		    struct cgroup *from, struct cgroup *to)
 {
 	struct fcg_cgrp_ctx *from_cgc, *to_cgc;
-	s64 vtime_delta;
+	s64 delta;
 
 	/* find_cgrp_ctx() triggers scx_ops_error() on lookup failures */
 	if (!(from_cgc = find_cgrp_ctx(from)) || !(to_cgc = find_cgrp_ctx(to)))
 		return;
 
-	vtime_delta = p->scx.dsq_vtime - from_cgc->tvtime_now;
-	p->scx.dsq_vtime = to_cgc->tvtime_now + vtime_delta;
+	delta = time_delta(p->scx.dsq_vtime, from_cgc->tvtime_now);
+	p->scx.dsq_vtime = to_cgc->tvtime_now + delta;
 }
 
 s32 BPF_STRUCT_OPS_SLEEPABLE(fcg_init)
diff --git a/tools/sched_ext/scx_simple.bpf.c b/tools/sched_ext/scx_simple.bpf.c
index 31f915b286c6..e6de99dba7db 100644
--- a/tools/sched_ext/scx_simple.bpf.c
+++ b/tools/sched_ext/scx_simple.bpf.c
@@ -52,11 +52,6 @@ static void stat_inc(u32 idx)
 		(*cnt_p)++;
 }
 
-static inline bool vtime_before(u64 a, u64 b)
-{
-	return (s64)(a - b) < 0;
-}
-
 s32 BPF_STRUCT_OPS(simple_select_cpu, struct task_struct *p, s32 prev_cpu, u64 wake_flags)
 {
 	bool is_idle = false;
@@ -84,7 +79,7 @@ void BPF_STRUCT_OPS(simple_enqueue, struct task_struct *p, u64 enq_flags)
 		 * Limit the amount of budget that an idling task can accumulate
 		 * to one slice.
 		 */
-		if (vtime_before(vtime, vtime_now - SCX_SLICE_DFL))
+		if (time_before(vtime, vtime_now - SCX_SLICE_DFL))
 			vtime = vtime_now - SCX_SLICE_DFL;
 
 		scx_bpf_dsq_insert_vtime(p, SHARED_DSQ, SCX_SLICE_DFL, vtime,
@@ -108,7 +103,7 @@ void BPF_STRUCT_OPS(simple_running, struct task_struct *p)
 	 * thus racy. Any error should be contained and temporary. Let's just
 	 * live with it.
 	 */
-	if (vtime_before(vtime_now, p->scx.dsq_vtime))
+	if (time_before(vtime_now, p->scx.dsq_vtime))
 		vtime_now = p->scx.dsq_vtime;
 }
 
-- 
2.47.1