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scx_layered: Don't call scx_bpf_cpuperf_set() unnecessarily

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layered_running() is calling scx_bpf_cpuperf_set() whenever a task of a
layer w/ cpuperf setting starts running which can be every task switch.
There's no reason to repeatedly call with the same value. Remember the last
value and call iff the new value is different.

This reduces the bpftop reported CPU consumption of scx_bpf_cpuperf_set()
from ~1.2% to ~0.7% while running rd-hashd at full CPU saturation on Ryzen
3900x.
This commit is contained in:
Tejun Heo 2024-11-16 05:45:44 -10:00
parent 75dd81e3e6
commit 51d4945d69
2 changed files with 4 additions and 1 deletions
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1
scheds/rust/scx_layered/src/bpf/intf.h
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@ -115,6 +115,7 @@ struct cpu_ctx {
u32 layer_idx; u32 layer_idx;
u32 cache_idx; u32 cache_idx;
u32 node_idx; u32 node_idx;
u32 perf;
}; };
struct cache_ctx { struct cache_ctx {

4
scheds/rust/scx_layered/src/bpf/main.bpf.c
View File

@ -2136,8 +2136,10 @@ void BPF_STRUCT_OPS(layered_running, struct task_struct *p)
} }
} }
if (layer->perf > 0) if (layer->perf > 0 && cctx->perf != layer->perf) {
scx_bpf_cpuperf_set(task_cpu, layer->perf); scx_bpf_cpuperf_set(task_cpu, layer->perf);
cctx->perf = layer->perf;
}
cctx->maybe_idle = false; cctx->maybe_idle = false;
} }