linux-next/tools/sched_ext/scx_simple.bpf.c

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * A simple scheduler.
 *
 * A simple global FIFO scheduler. It also demonstrates the following niceties.
 *
 * - Statistics tracking how many tasks are queued to local and global dsq's.
 * - Termination notification for userspace.
 *
 * Copyright (c) 2022 Meta Platforms, Inc. and affiliates.
 * Copyright (c) 2022 Tejun Heo <tj@kernel.org>
 * Copyright (c) 2022 David Vernet <dvernet@meta.com>
 */
#include <scx/common.bpf.h>

char _license[] SEC("license") = "GPL";

UEI_DEFINE(uei);

struct {
	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
	__uint(key_size, sizeof(u32));
	__uint(value_size, sizeof(u64));
	__uint(max_entries, 2);			/* [local, global] */
} stats SEC(".maps");

static void stat_inc(u32 idx)
{
	u64 *cnt_p = bpf_map_lookup_elem(&stats, &idx);
	if (cnt_p)
		(*cnt_p)++;
}

s32 BPF_STRUCT_OPS(simple_select_cpu, struct task_struct *p, s32 prev_cpu, u64 wake_flags)
{
	bool is_idle = false;
	s32 cpu;

	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);
	}

	return cpu;
}

void BPF_STRUCT_OPS(simple_enqueue, struct task_struct *p, u64 enq_flags)
{
	stat_inc(1);	/* count global queueing */
	scx_bpf_dispatch(p, SCX_DSQ_GLOBAL, SCX_SLICE_DFL, enq_flags);
}

void BPF_STRUCT_OPS(simple_exit, struct scx_exit_info *ei)
{
	UEI_RECORD(uei, ei);
}

SCX_OPS_DEFINE(simple_ops,
	       .select_cpu		= (void *)simple_select_cpu,
	       .enqueue			= (void *)simple_enqueue,
	       .exit			= (void *)simple_exit,
	       .name			= "simple");