1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * A scheduler that validates that enqueue flags are properly stored and 4 * applied at dispatch time when a task is directly dispatched from 5 * ops.select_cpu(). We validate this by using scx_bpf_dispatch_vtime(), and 6 * making the test a very basic vtime scheduler. 7 * 8 * Copyright (c) 2024 Meta Platforms, Inc. and affiliates. 9 * Copyright (c) 2024 David Vernet <dvernet@meta.com> 10 * Copyright (c) 2024 Tejun Heo <tj@kernel.org> 11 */ 12 13 #include <scx/common.bpf.h> 14 15 char _license[] SEC("license") = "GPL"; 16 17 volatile bool consumed; 18 19 static u64 vtime_now; 20 21 #define VTIME_DSQ 0 22 23 static inline bool vtime_before(u64 a, u64 b) 24 { 25 return (s64)(a - b) < 0; 26 } 27 28 static inline u64 task_vtime(const struct task_struct *p) 29 { 30 u64 vtime = p->scx.dsq_vtime; 31 32 if (vtime_before(vtime, vtime_now - SCX_SLICE_DFL)) 33 return vtime_now - SCX_SLICE_DFL; 34 else 35 return vtime; 36 } 37 38 s32 BPF_STRUCT_OPS(select_cpu_vtime_select_cpu, struct task_struct *p, 39 s32 prev_cpu, u64 wake_flags) 40 { 41 s32 cpu; 42 43 cpu = scx_bpf_pick_idle_cpu(p->cpus_ptr, 0); 44 if (cpu >= 0) 45 goto ddsp; 46 47 cpu = prev_cpu; 48 scx_bpf_test_and_clear_cpu_idle(cpu); 49 ddsp: 50 scx_bpf_dispatch_vtime(p, VTIME_DSQ, SCX_SLICE_DFL, task_vtime(p), 0); 51 return cpu; 52 } 53 54 void BPF_STRUCT_OPS(select_cpu_vtime_dispatch, s32 cpu, struct task_struct *p) 55 { 56 if (scx_bpf_consume(VTIME_DSQ)) 57 consumed = true; 58 } 59 60 void BPF_STRUCT_OPS(select_cpu_vtime_running, struct task_struct *p) 61 { 62 if (vtime_before(vtime_now, p->scx.dsq_vtime)) 63 vtime_now = p->scx.dsq_vtime; 64 } 65 66 void BPF_STRUCT_OPS(select_cpu_vtime_stopping, struct task_struct *p, 67 bool runnable) 68 { 69 p->scx.dsq_vtime += (SCX_SLICE_DFL - p->scx.slice) * 100 / p->scx.weight; 70 } 71 72 void BPF_STRUCT_OPS(select_cpu_vtime_enable, struct task_struct *p) 73 { 74 p->scx.dsq_vtime = vtime_now; 75 } 76 77 s32 BPF_STRUCT_OPS_SLEEPABLE(select_cpu_vtime_init) 78 { 79 return scx_bpf_create_dsq(VTIME_DSQ, -1); 80 } 81 82 SEC(".struct_ops.link") 83 struct sched_ext_ops select_cpu_vtime_ops = { 84 .select_cpu = (void *) select_cpu_vtime_select_cpu, 85 .dispatch = (void *) select_cpu_vtime_dispatch, 86 .running = (void *) select_cpu_vtime_running, 87 .stopping = (void *) select_cpu_vtime_stopping, 88 .enable = (void *) select_cpu_vtime_enable, 89 .init = (void *) select_cpu_vtime_init, 90 .name = "select_cpu_vtime", 91 .timeout_ms = 1000U, 92 }; 93