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scx_lavd: direct dispatch when there is an idle CPU

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When there is an idle CPU, direct dispatch is performed to reduce
scheduling latency. This didn't work well before, but it seems
to work well now with other tunings.

Signed-off-by: Changwoo Min <changwoo@igalia.com>
This commit is contained in:
Changwoo Min 2024-10-20 15:42:27 +09:00
parent 420de70159
commit 5a852dc3d9
1 changed files with 18 additions and 10 deletions
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28
scheds/rust/scx_lavd/src/bpf/main.bpf.c
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@ -911,6 +911,15 @@ out:
return cpu_id; return cpu_id;
} }
static void update_task_log_clk(struct task_ctx *taskc)
{
/*
* Update the logical clock of the virtual deadline.
*/
u64 vlc = READ_ONCE(cur_logical_clk) + taskc->vdeadline_delta_ns;
WRITE_ONCE(taskc->vdeadline_log_clk, vlc);
}
s32 BPF_STRUCT_OPS(lavd_select_cpu, struct task_struct *p, s32 prev_cpu, s32 BPF_STRUCT_OPS(lavd_select_cpu, struct task_struct *p, s32 prev_cpu,
u64 wake_flags) u64 wake_flags)
{ {
@ -923,31 +932,30 @@ s32 BPF_STRUCT_OPS(lavd_select_cpu, struct task_struct *p, s32 prev_cpu,
return prev_cpu; return prev_cpu;
cpu_id = pick_idle_cpu(p, taskc, prev_cpu, wake_flags, &found_idle); cpu_id = pick_idle_cpu(p, taskc, prev_cpu, wake_flags, &found_idle);
if (found_idle) if (found_idle) {
taskc->vdeadline_delta_ns = 0;
update_task_log_clk(taskc);
p->scx.slice = calc_time_slice(p, taskc);
scx_bpf_dispatch(p, SCX_DSQ_LOCAL, p->scx.slice, 0);
return cpu_id; return cpu_id;
}
taskc->wakeup_ft += !!(wake_flags & SCX_WAKE_SYNC); taskc->wakeup_ft += !!(wake_flags & SCX_WAKE_SYNC);
return (cpu_id >= 0) ? cpu_id : prev_cpu; return prev_cpu;
} }
static void calc_when_to_run(struct task_struct *p, struct task_ctx *taskc, static void calc_when_to_run(struct task_struct *p, struct task_ctx *taskc,
struct cpu_ctx *cpuc_cur, u64 enq_flags) struct cpu_ctx *cpuc_cur, u64 enq_flags)
{ {
u64 vlc;
/* /*
* Before enqueueing a task to a run queue, we should decide when a * Before enqueueing a task to a run queue, we should decide when a
* task should be scheduled. * task should be scheduled.
*/ */
calc_virtual_deadline_delta(p, taskc, cpuc_cur, enq_flags); calc_virtual_deadline_delta(p, taskc, cpuc_cur, enq_flags);
/* update_task_log_clk(taskc);
* Update the logical clock of the virtual deadline.
*/
vlc = READ_ONCE(cur_logical_clk) + taskc->vdeadline_delta_ns;
WRITE_ONCE(taskc->vdeadline_log_clk, vlc);
} }
static u64 find_proper_dsq(struct task_ctx *taskc, struct cpu_ctx *cpuc) static u64 find_proper_dsq(struct task_ctx *taskc, struct cpu_ctx *cpuc)