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/* 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");
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