/* SPDX-License-Identifier: GPL-2.0 */
/*
* A scheduler that validates the behavior of direct dispatching with a default
* select_cpu implementation, and with the SCX_OPS_ENQ_DFL_NO_DISPATCH ops flag
* specified.
*
* Copyright (c) 2023 Meta Platforms, Inc. and affiliates.
* Copyright (c) 2023 David Vernet <[email protected]>
* Copyright (c) 2023 Tejun Heo <[email protected]>
*/
#include <scx/common.bpf.h>
char _license[] SEC("license") = "GPL";
bool saw_local = false;
/* Per-task scheduling context */
struct task_ctx {
bool force_local; /* CPU changed by ops.select_cpu() */
};
struct {
__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
__uint(map_flags, BPF_F_NO_PREALLOC);
__type(key, int);
__type(value, struct task_ctx);
} task_ctx_stor SEC(".maps");
/* Manually specify the signature until the kfunc is added to the scx repo. */
s32 scx_bpf_select_cpu_dfl(struct task_struct *p, s32 prev_cpu, u64 wake_flags,
bool *found) __ksym;
s32 BPF_STRUCT_OPS(select_cpu_dfl_nodispatch_select_cpu, struct task_struct *p,
s32 prev_cpu, u64 wake_flags)
{
struct task_ctx *tctx;
s32 cpu;
tctx = bpf_task_storage_get(&task_ctx_stor, p, 0, 0);
if (!tctx) {
scx_bpf_error("task_ctx lookup failed");
return -ESRCH;
}
cpu = scx_bpf_select_cpu_dfl(p, prev_cpu, wake_flags,
&tctx->force_local);
return cpu;
}
void BPF_STRUCT_OPS(select_cpu_dfl_nodispatch_enqueue, struct task_struct *p,
u64 enq_flags)
{
u64 dsq_id = SCX_DSQ_GLOBAL;
struct task_ctx *tctx;
tctx = bpf_task_storage_get(&task_ctx_stor, p, 0, 0);
if (!tctx) {
scx_bpf_error("task_ctx lookup failed");
return;
}
if (tctx->force_local) {
dsq_id = SCX_DSQ_LOCAL;
tctx->force_local = false;
saw_local = true;
}
scx_bpf_dispatch(p, dsq_id, SCX_SLICE_DFL, enq_flags);
}
s32 BPF_STRUCT_OPS(select_cpu_dfl_nodispatch_init_task,
struct task_struct *p, struct scx_init_task_args *args)
{
if (bpf_task_storage_get(&task_ctx_stor, p, 0,
BPF_LOCAL_STORAGE_GET_F_CREATE))
return 0;
else
return -ENOMEM;
}
SEC(".struct_ops.link")
struct sched_ext_ops select_cpu_dfl_nodispatch_ops = {
.select_cpu = select_cpu_dfl_nodispatch_select_cpu,
.enqueue = select_cpu_dfl_nodispatch_enqueue,
.init_task = select_cpu_dfl_nodispatch_init_task,
.name = "select_cpu_dfl_nodispatch",
};