From 57d4ae243a92253d48021483fc58e27d42299b5a Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Mon, 2 Mar 2026 06:45:25 +0000
Subject: [PATCH] Add sys util to get rss from statm on linux.

Signed-off-by: Jason Volk <jason@zemos.net>
---
 src/core/utils/sys.rs       |  6 +++-
 src/core/utils/sys/usage.rs | 66 ++++++++++++++++++++++++++++++++++++-
 2 files changed, 70 insertions(+), 2 deletions(-)

diff --git a/src/core/utils/sys.rs b/src/core/utils/sys.rs
index 43712487..efa9925f 100644
--- a/src/core/utils/sys.rs
+++ b/src/core/utils/sys.rs
@@ -5,7 +5,11 @@ pub mod usage;
 
 use std::path::PathBuf;
 
-pub use self::{compute::available_parallelism, limits::*, usage::*};
+pub use self::{
+	compute::available_parallelism,
+	limits::*,
+	usage::{statm, thread_usage, usage},
+};
 use crate::{Result, at};
 
 /// Return a possibly corrected std::env::current_exe() even if the path is
diff --git a/src/core/utils/sys/usage.rs b/src/core/utils/sys/usage.rs
index 6bf6f01a..423cc8fa 100644
--- a/src/core/utils/sys/usage.rs
+++ b/src/core/utils/sys/usage.rs
@@ -1,8 +1,72 @@
+use std::{fs::File, io::Read, str};
+
 use nix::sys::resource::Usage;
 #[cfg(unix)]
 use nix::sys::resource::{UsageWho, getrusage};
 
-use crate::Result;
+use crate::{Error, Result, arrayvec::ArrayVec, expected};
+
+pub fn virt() -> Result<usize> {
+	Ok(statm_bytes()?
+		.next()
+		.expect("incomplete statm contents"))
+}
+
+pub fn res() -> Result<usize> {
+	Ok(statm_bytes()?
+		.nth(1)
+		.expect("incomplete statm contents"))
+}
+
+pub fn shm() -> Result<usize> {
+	Ok(statm_bytes()?
+		.nth(2)
+		.expect("incomplete statm contents"))
+}
+
+pub fn code() -> Result<usize> {
+	Ok(statm_bytes()?
+		.nth(3)
+		.expect("incomplete statm contents"))
+}
+
+pub fn data() -> Result<usize> {
+	Ok(statm_bytes()?
+		.nth(5)
+		.expect("incomplete statm contents"))
+}
+
+#[inline]
+pub fn statm_bytes() -> Result<impl Iterator<Item = usize>> {
+	let page_size = super::page_size()?;
+
+	Ok(statm()?.map(move |pages| expected!(pages * page_size)))
+}
+
+#[cfg(target_os = "linux")]
+#[inline]
+pub fn statm() -> Result<impl Iterator<Item = usize>> {
+	File::open("/proc/self/statm")
+		.map_err(Error::from)
+		.and_then(|mut fp| {
+			let mut buf = [0; 96];
+			let len = fp.read(&mut buf)?;
+			let vals = str::from_utf8(&buf[0..len])
+				.expect("non-utf8 content in statm")
+				.split_ascii_whitespace()
+				.map(|val| {
+					val.parse()
+						.expect("non-integer value in statm contents")
+				})
+				.collect::<ArrayVec<usize, 12>>();
+
+			Ok(vals.into_iter())
+		})
+}
+
+#[cfg(not(target_os = "linux"))]
+#[inline]
+pub fn statm() -> Result<usize> { Err!("proc_pid_statm(5) only available on linux systems") }
 
 #[cfg(unix)]
 pub fn usage() -> Result<Usage> { getrusage(UsageWho::RUSAGE_SELF).map_err(Into::into) }