add utils to detect device io characteristics

Signed-off-by: Jason Volk <jason@zemos.net>

src/core/utils/sys/storage.rs

@@ -0,0 +1,112 @@
+//! System utilities related to devices/peripherals
+
+use std::{
+	ffi::{OsStr, OsString},
+	fs,
+	fs::{read_to_string, FileType},
+	iter::IntoIterator,
+	path::Path,
+};
+
+use crate::{result::FlatOk, Result};
+
+/// Device characteristics useful for random access throughput
+#[derive(Clone, Debug, Default)]
+pub struct Parallelism {
+	/// Number of requests for the device.
+	pub nr_requests: Option<usize>,
+
+	/// Individual queue characteristics.
+	pub mq: Vec<Queue>,
+}
+
+/// Device queue characteristics
+#[derive(Clone, Debug, Default)]
+pub struct Queue {
+	/// Queue's indice.
+	pub id: usize,
+
+	/// Number of requests for the queue.
+	pub nr_tags: Option<usize>,
+
+	/// CPU affinities for the queue.
+	pub cpu_list: Vec<usize>,
+}
+
+/// Get device characteristics useful for random access throughput by name.
+#[must_use]
+pub fn parallelism(name: &OsStr) -> Parallelism {
+	let name = name
+		.to_str()
+		.expect("device name expected to be utf-8 representable");
+
+	let block_path = Path::new("/").join("sys/").join("block/");
+
+	let mq_path = Path::new(&block_path).join(format!("{name}/mq/"));
+
+	let nr_requests_path = Path::new(&block_path).join(format!("{name}/queue/nr_requests"));
+
+	Parallelism {
+		nr_requests: read_to_string(&nr_requests_path)
+			.ok()
+			.as_deref()
+			.map(str::trim)
+			.map(str::parse)
+			.flat_ok(),
+
+		mq: fs::read_dir(&mq_path)
+			.into_iter()
+			.flat_map(IntoIterator::into_iter)
+			.filter_map(Result::ok)
+			.filter(|entry| entry.file_type().as_ref().is_ok_and(FileType::is_dir))
+			.map(|dir| queue_parallelism(&dir.path()))
+			.collect(),
+	}
+}
+
+/// Get device queue characteristics by mq path on sysfs(5)
+fn queue_parallelism(dir: &Path) -> Queue {
+	let queue_id = dir.file_name();
+
+	let nr_tags_path = dir.join("nr_tags");
+
+	let cpu_list_path = dir.join("cpu_list");
+
+	Queue {
+		id: queue_id
+			.and_then(OsStr::to_str)
+			.map(str::parse)
+			.flat_ok()
+			.expect("queue has some numerical identifier"),
+
+		nr_tags: read_to_string(&nr_tags_path)
+			.ok()
+			.as_deref()
+			.map(str::trim)
+			.map(str::parse)
+			.flat_ok(),
+
+		cpu_list: read_to_string(&cpu_list_path)
+			.iter()
+			.flat_map(|list| list.trim().split(','))
+			.map(str::trim)
+			.map(str::parse)
+			.filter_map(Result::ok)
+			.collect(),
+	}
+}
+
+/// Get the name of the device on which Path is mounted.
+#[must_use]
+pub fn name_from_path(path: &Path) -> Option<OsString> {
+	sysinfo::Disks::new_with_refreshed_list()
+		.into_iter()
+		.filter(|disk| path.starts_with(disk.mount_point()))
+		.max_by(|a, b| {
+			let a = a.mount_point().ancestors().count();
+			let b = b.mount_point().ancestors().count();
+			a.cmp(&b)
+		})
+		.map(|disk| Path::new(disk.name()))
+		.and_then(|path| path.file_name().map(ToOwned::to_owned))
+}