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scx_lavd: Factor the task's runtime more aggressively in a deadline calculation

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Instead of using a constant runtime value in the deadline calculation,
use the adjusted runtime value of a task. Since tasks' runtime value
follows a highly skewed distribution, we convert the highly skewed
distribution to a mildly skewed distribution to avoid stalls. This
resolves the audio breaking issue in osu! under heavy background workloads.

Signed-off-by: Changwoo Min <changwoo@igalia.com>
This commit is contained in:
Changwoo Min 2024-11-18 11:43:30 +09:00
parent 66223bf235
commit 3292be7b72
1 changed files with 18 additions and 6 deletions
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24
scheds/rust/scx_lavd/src/bpf/main.bpf.c
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@ -334,9 +334,9 @@ static u64 calc_lat_cri(struct task_struct *p, struct task_ctx *taskc,
* add +1 to guarantee the latency criticality (log2-ed) is always
* positive.
*/
lat_cri = log2_u64(runtime_ft + 1);
lat_cri += log2_u64(wait_freq_ft + 1);
lat_cri += log2_u64(wake_freq_ft + 1);
lat_cri = log2_u64(wait_freq_ft);
lat_cri += log2_u64(wake_freq_ft);
lat_cri += log2_u64(runtime_ft);
/*
* Make sure the lat_cri is non-zero.
@ -353,21 +353,33 @@ static u64 calc_lat_cri(struct task_struct *p, struct task_ctx *taskc,
return taskc->lat_cri;
}
static u64 calc_adj_runtime(u64 runtime)
{
/*
* Convert highly skewed runtime distribution to
* mildlyskewed distribution.
*/
u64 adj_runtime = log2_u64(runtime + 1);
return adj_runtime * adj_runtime;
}
static void calc_virtual_deadline_delta(struct task_struct *p,
struct task_ctx *taskc,
u64 enq_flags)
{
u64 deadline, lat_cri;
u64 deadline, lat_cri, adj_runtime;
u32 greedy_ratio, greedy_ft;
/*
* Calculate the deadline based on latency criticality and greedy ratio.
* Calculate the deadline based on runtime,
* latency criticality, and greedy ratio.
*/
lat_cri = calc_lat_cri(p, taskc, enq_flags);
greedy_ratio = calc_greedy_ratio(taskc);
greedy_ft = calc_greedy_factor(greedy_ratio);
adj_runtime = calc_adj_runtime(taskc->run_time_ns);
deadline = (LAVD_SLICE_MAX_NS / lat_cri) * greedy_ft;
deadline = (adj_runtime / lat_cri) * greedy_ft;
taskc->vdeadline_delta_ns = deadline;
}