scx_utils: Add netdev support

Add support for collecting network device support for use in topology
awareness.

Signed-off-by: Daniel Hodges <hodges.daniel.scott@gmail.com>

rust/scx_utils/src/cpumask.rs

@@ -68,7 +68,7 @@ use std::ops::BitOrAssign;
 use std::ops::BitXor;
 use std::ops::BitXorAssign;
 
-#[derive(Debug, Eq, Clone, Ord, PartialEq, PartialOrd)]
+#[derive(Debug, Eq, Clone, Hash, Ord, PartialEq, PartialOrd)]
 pub struct Cpumask {
     mask: BitVec<u64, Lsb0>,
 }
@@ -146,6 +146,10 @@ impl Cpumask {
         }
     }
 
+    pub fn from_bitvec(bitvec: BitVec<u64, Lsb0>) -> Self {
+        Self { mask: bitvec }
+    }
+
     /// Return a slice of u64's whose bits reflect the Cpumask.
     pub fn as_raw_slice(&self) -> &[u64] {
         self.mask.as_raw_slice()

rust/scx_utils/src/lib.rs

@@ -88,5 +88,9 @@ pub use misc::monitor_stats;
 pub use misc::normalize_load_metric;
 pub use misc::set_rlimit_infinity;
 
+mod netdev;
+pub use netdev::read_netdevs;
+pub use netdev::NetDev;
+
 pub mod enums;
 pub use enums::scx_enums;

rust/scx_utils/src/netdev.rs

@@ -0,0 +1,83 @@
+// Copyright (c) Meta Platforms, Inc. and affiliates.
+
+// This software may be used and distributed according to the terms of the
+// GNU General Public License version 2.
+
+use std::collections::BTreeMap;
+use std::fs;
+use std::path::Path;
+
+use crate::misc::read_file_usize;
+use crate::Cpumask;
+use anyhow::Result;
+
+#[derive(Debug, Clone, Eq, Hash, Ord, PartialEq, PartialOrd)]
+pub struct NetDev {
+    pub iface: String,
+    pub node: usize,
+    pub irqs: BTreeMap<usize, Cpumask>,
+    pub irq_hints: BTreeMap<usize, Cpumask>,
+}
+
+impl NetDev {
+    pub fn apply_cpumasks(&self) -> Result<()> {
+        for (irq, cpumask) in self.irqs.iter() {
+            let irq_path = format!("/proc/irq/{}/smp_affinity", irq);
+            fs::write(irq_path, format!("{:#x}", cpumask))?
+        }
+        Ok(())
+    }
+}
+
+pub fn read_netdevs() -> Result<BTreeMap<String, NetDev>> {
+    let mut netdevs: BTreeMap<String, NetDev> = BTreeMap::new();
+
+    for entry in fs::read_dir("/sys/class/net")? {
+        let entry = entry?;
+        let iface = entry.file_name().to_string_lossy().into_owned();
+        let raw_path = format!("/sys/class/net/{}/device/msi_irqs", iface);
+        let msi_irqs_path = Path::new(&raw_path);
+        if !msi_irqs_path.exists() {
+            continue;
+        }
+
+        let node_path_raw = format!("/sys/class/net/{}/device/node", iface);
+        let node_path = Path::new(&node_path_raw);
+        let node = read_file_usize(node_path).unwrap_or(0);
+        let mut irqs = BTreeMap::new();
+        let mut irq_hints = BTreeMap::new();
+
+        for entry in fs::read_dir(msi_irqs_path)? {
+            let entry = entry.unwrap();
+            let irq = entry.file_name().to_string_lossy().into_owned();
+            if let Ok(irq) = irq.parse::<usize>() {
+                let affinity_raw_path = format!("/proc/irq/{}/smp_affinity", irq);
+                let smp_affinity_path = Path::new(&affinity_raw_path);
+                let smp_affinity = fs::read_to_string(smp_affinity_path)?
+                    .replace(",", "")
+                    .replace("\n", "");
+                let cpumask = Cpumask::from_str(&smp_affinity)?;
+                irqs.insert(irq, cpumask);
+
+                // affinity hints
+                let affinity_hint_raw_path = format!("/proc/irq/{}/affinity_hint", irq);
+                let affinity_hint_path = Path::new(&affinity_hint_raw_path);
+                let affinity_hint = fs::read_to_string(affinity_hint_path)?
+                    .replace(",", "")
+                    .replace("\n", "");
+                let hint_cpumask = Cpumask::from_str(&affinity_hint)?;
+                irq_hints.insert(irq, hint_cpumask);
+            }
+        }
+        netdevs.insert(
+            iface.clone(),
+            NetDev {
+                iface,
+                node,
+                irqs,
+                irq_hints,
+            },
+        );
+    }
+    Ok(netdevs)
+}

scheds/rust/scx_layered/src/lib.rs

@@ -222,6 +222,15 @@ impl CpuPool {
         Ok(Some(&self.core_cpus[core]))
     }
 
+    pub fn available_cpus(&self) -> BitVec<u64, Lsb0> {
+        let mut cpus = bitvec![u64, Lsb0; 0; self.nr_cpus];
+        for core in self.available_cores.iter_ones() {
+            let core_cpus = self.core_cpus[core].clone();
+            cpus |= core_cpus.as_bitslice();
+        }
+        cpus
+    }
+
     pub fn available_cpus_in_mask(&self, allowed_cpus: &BitVec) -> BitVec {
         let mut cpus = bitvec![0; self.nr_cpus];
         for core in self.available_cores.iter_ones() {

scheds/rust/scx_layered/src/main.rs

@@ -44,6 +44,7 @@ use scx_utils::compat;
 use scx_utils::import_enums;
 use scx_utils::init_libbpf_logging;
 use scx_utils::ravg::ravg_read;
+use scx_utils::read_netdevs;
 use scx_utils::scx_enums;
 use scx_utils::scx_ops_attach;
 use scx_utils::scx_ops_load;
@@ -53,6 +54,7 @@ use scx_utils::uei_report;
 use scx_utils::Cache;
 use scx_utils::CoreType;
 use scx_utils::LoadAggregator;
+use scx_utils::NetDev;
 use scx_utils::Topology;
 use scx_utils::UserExitInfo;
 use stats::LayerStats;
@@ -471,6 +473,10 @@ struct Opts {
     #[clap(long, default_value = "false")]
     disable_antistall: bool,
 
+    /// Enable netdev IRQ balancing
+    #[clap(long, default_value = "false")]
+    netdev_irq_balance: bool,
+
     /// Maximum task runnable_at delay (in seconds) before antistall turns on
     #[clap(long, default_value = "3")]
     antistall_sec: u64,
@@ -1215,6 +1221,7 @@ struct Scheduler<'a> {
     nr_layer_cpus_ranges: Vec<(usize, usize)>,
     processing_dur: Duration,
 
+    netdevs: BTreeMap<String, NetDev>,
     stats_server: StatsServer<StatsReq, StatsRes>,
 }
 
@@ -1399,6 +1406,12 @@ impl<'a> Scheduler<'a> {
         let topo = Topology::new()?;
         let cpu_pool = CpuPool::new(&topo)?;
 
+        let netdevs = if opts.netdev_irq_balance {
+            read_netdevs()?
+        } else {
+            BTreeMap::new()
+        };
+
         let disable_topology = if let Some(val) = opts.disable_topology {
             val
         } else {
@@ -1523,6 +1536,7 @@ impl<'a> Scheduler<'a> {
             proc_reader,
             skel,
 
+            netdevs,
             stats_server,
         };
 
@@ -1542,6 +1556,26 @@ impl<'a> Scheduler<'a> {
         bpf_layer.refresh_cpus = 1;
     }
 
+    fn update_netdev_cpumasks(&mut self) -> Result<()> {
+        let available_cpus = self.cpu_pool.available_cpus();
+        if available_cpus.is_empty() {
+            return Ok(());
+        }
+
+        for (iface, netdev) in self.netdevs.iter_mut() {
+            for (irq, irqmask) in netdev.irqs.iter_mut() {
+                irqmask.clear();
+                for cpu in available_cpus.iter_ones() {
+                    let _ = irqmask.set_cpu(cpu);
+                }
+                trace!("{} updating irq {} cpumask {:?}", iface, irq, irqmask);
+            }
+            netdev.apply_cpumasks()?;
+        }
+
+        Ok(())
+    }
+
     fn set_bpf_layer_preemption(layer: &mut Layer, bpf_layer: &mut types::layer, preempt: bool) {
         layer.preempt = preempt;
         bpf_layer.preempt.write(preempt);
@@ -1656,6 +1690,7 @@ impl<'a> Scheduler<'a> {
             }
         }
 
+        let _ = self.update_netdev_cpumasks();
         Ok(())
     }