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scx_bpfland: dynamically adjust cpufreq level in auto mode

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In auto mode, rather than keeping the previous fixed cpuperf factor,
dynamically calculate it based on CPU utilization and apply it before a
task runs within its allocated time slot.

Interactive tasks consistently receive the maximum scaling factor to
ensure optimal performance.

Signed-off-by: Andrea Righi <andrea.righi@linux.dev>
This commit is contained in:
Andrea Righi 2024-09-03 21:25:37 +02:00
parent fe6ac15015
commit 918f1db4bd
1 changed files with 68 additions and 12 deletions
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80
scheds/rust/scx_bpfland/src/bpf/main.bpf.c
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@ -192,6 +192,9 @@ static u64 vtime_now;
* Per-CPU context.
*/
struct cpu_ctx {
u64 tot_runtime;
u64 prev_runtime;
u64 last_running;
struct bpf_cpumask __kptr *l2_cpumask;
struct bpf_cpumask __kptr *l3_cpumask;
};
@ -542,7 +545,7 @@ static s32 pick_idle_cpu(struct task_struct *p, s32 prev_cpu, bool do_turbo)
* idle state.
*/
if (p->nr_cpus_allowed == 1) {
if (is_kthread(p) && local_kthreads ||
if ((is_kthread(p) && local_kthreads) ||
scx_bpf_test_and_clear_cpu_idle(prev_cpu))
return prev_cpu;
return -ENOENT;
@ -1008,12 +1011,61 @@ void BPF_STRUCT_OPS(bpfland_dispatch, s32 cpu, struct task_struct *prev)
prev->scx.slice = task_slice(prev);
}
/*
* Scale target CPU frequency based on the performance level selected
* from user-space and the CPU utilization.
*/
static void update_cpuperf_target(struct task_struct *p)
{
u64 now = bpf_ktime_get_ns();
s32 cpu = scx_bpf_task_cpu(p);
u64 perf_lvl, delta_runtime, delta_t;
struct cpu_ctx *cctx;
if (cpufreq_perf_lvl >= 0) {
/*
* Apply fixed cpuperf scaling factor determined by user-space.
*/
perf_lvl = MIN(cpufreq_perf_lvl, SCX_CPUPERF_ONE);
scx_bpf_cpuperf_set(cpu, perf_lvl);
return;
}
/*
* Auto mode: always tset max performance for interactive tasks.
*/
if (is_task_interactive(p)) {
scx_bpf_cpuperf_set(cpu, SCX_CPUPERF_ONE);
return;
}
/*
* For non-interactive tasks determine their cpufreq scaling factor as
* a function of their CPU utilization.
*/
cctx = try_lookup_cpu_ctx(cpu);
if (!cctx)
return;
/*
* Evaluate dynamic cpuperf scaling factor using the average CPU
* utilization, normalized in the range [0 .. SCX_CPUPERF_ONE].
*/
delta_t = now - cctx->last_running;
delta_runtime = cctx->tot_runtime - cctx->prev_runtime;
perf_lvl = MIN(delta_runtime * SCX_CPUPERF_ONE / delta_t, SCX_CPUPERF_ONE);
/*
* Apply the dynamic cpuperf scaling factor.
*/
scx_bpf_cpuperf_set(cpu, perf_lvl);
cctx->last_running = bpf_ktime_get_ns();
cctx->prev_runtime = cctx->tot_runtime;
}
void BPF_STRUCT_OPS(bpfland_running, struct task_struct *p)
{
s32 cpu = scx_bpf_task_cpu(p);
u32 cap, cur;
u64 perf_lvl;
/* Update global vruntime */
if (vtime_before(vtime_now, p->scx.dsq_vtime))
vtime_now = p->scx.dsq_vtime;
@ -1025,15 +1077,13 @@ void BPF_STRUCT_OPS(bpfland_running, struct task_struct *p)
p->scx.slice = task_slice(p);
/*
* Scale target CPU frequency based on the performance level selected
* from user-space.
* Adjust target CPU frequency before the task starts to run.
*/
if (cpufreq_perf_lvl >= 0) {
perf_lvl = MIN(cpufreq_perf_lvl, SCX_CPUPERF_ONE);
scx_bpf_cpuperf_set(cpu, perf_lvl);
}
update_cpuperf_target(p);
/* Update CPU interactive state */
/*
* Update CPU interactive state.
*/
if (is_task_interactive(p))
__sync_fetch_and_add(&nr_interactive, 1);
@ -1061,9 +1111,15 @@ static void update_task_interactive(struct task_ctx *tctx)
void BPF_STRUCT_OPS(bpfland_stopping, struct task_struct *p, bool runnable)
{
u64 now = bpf_ktime_get_ns();
s32 cpu = scx_bpf_task_cpu(p);
s64 delta_t;
struct cpu_ctx *cctx;
struct task_ctx *tctx;
cctx = try_lookup_cpu_ctx(cpu);
if (cctx)
cctx->tot_runtime += now - cctx->last_running;
__sync_fetch_and_sub(&nr_running, 1);
tctx = try_lookup_task_ctx(p);