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scx_layered: Use PROG_RUN to update cpumasks

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Use bpf PROG_RUN from userspace for updating cpumask for rather than
relying on scheduler ticks. This should be a lower overhead approach in
that an extra bpf program does not need to be called on every CPU during
tick.

Signed-off-by: Daniel Hodges <hodges.daniel.scott@gmail.com>
This commit is contained in:
Daniel Hodges 2024-11-20 13:22:35 -08:00
parent dabb4aff41
commit a86e62aa21
2 changed files with 18 additions and 16 deletions
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13
scheds/rust/scx_layered/src/bpf/main.bpf.c
View File

@ -322,8 +322,10 @@ static bool refresh_cpumasks(int idx)
if (!__sync_val_compare_and_swap(&layer->refresh_cpus, 1, 0))
return false;
bpf_rcu_read_lock();
if (!(cpumaskw = bpf_map_lookup_elem(&layer_cpumasks, &idx)) ||
!(layer_cpumask = cpumaskw->cpumask)) {
bpf_rcu_read_unlock();
scx_bpf_error("can't happen");
return false;
}
@ -332,6 +334,7 @@ static bool refresh_cpumasks(int idx)
u8 *u8_ptr;
if (!(cctx = lookup_cpu_ctx(cpu))) {
bpf_rcu_read_unlock();
scx_bpf_error("unknown cpu");
return false;
}
@ -351,6 +354,7 @@ static bool refresh_cpumasks(int idx)
layer->nr_cpus = total;
__sync_fetch_and_add(&layer->cpus_seq, 1);
bpf_rcu_read_unlock();
trace("LAYER[%d] now has %d cpus, seq=%llu", idx, layer->nr_cpus, layer->cpus_seq);
return total > 0;
}
@ -359,14 +363,17 @@ static bool refresh_cpumasks(int idx)
// defined after some helpers, but before it's helpers are used.
#include "cost.bpf.c"
SEC("fentry")
int BPF_PROG(sched_tick_fentry)
/*
* Refreshes all layer cpumasks, this is called via BPF_PROG_RUN from userspace.
*/
SEC("syscall")
int BPF_PROG(refresh_layer_cpumasks)
{
int idx;
if (bpf_get_smp_processor_id() == 0)
bpf_for(idx, 0, nr_layers)
refresh_cpumasks(idx);
return 0;
}

17
scheds/rust/scx_layered/src/main.rs
View File

@ -34,6 +34,7 @@ use libbpf_rs::skel::Skel;
use libbpf_rs::skel::SkelBuilder;
use libbpf_rs::MapCore as _;
use libbpf_rs::OpenObject;
use libbpf_rs::ProgramInput;
use log::debug;
use log::info;
use log::trace;
@ -1461,17 +1462,6 @@ impl<'a> Scheduler<'a> {
skel.maps.rodata_data.slice_ns = scx_enums.SCX_SLICE_DFL;
skel.maps.rodata_data.max_exec_ns = 20 * scx_enums.SCX_SLICE_DFL;
// scheduler_tick() got renamed to sched_tick() during v6.10-rc.
let sched_tick_name = match compat::ksym_exists("sched_tick")? {
true => "sched_tick",
false => "scheduler_tick",
};
skel.progs
.sched_tick_fentry
.set_attach_target(0, Some(sched_tick_name.into()))
.context("Failed to set attach target for sched_tick_fentry()")?;
// Initialize skel according to @opts.
skel.struct_ops.layered_mut().exit_dump_len = opts.exit_dump_len;
@ -1715,6 +1705,11 @@ impl<'a> Scheduler<'a> {
self.nr_layer_cpus_ranges[lidx].1.max(layer.nr_cpus),
);
}
let input = ProgramInput {
..Default::default()
};
let prog = &mut self.skel.progs.refresh_layer_cpumasks;
let _ = prog.test_run(input);
}
let _ = self.update_netdev_cpumasks();