use crate::util::{parse_cgroup_stat, read_cgroup_text};
use std::ffi::OsString;
use std::os::unix::ffi::OsStringExt;
use std::path::{Component, Path, PathBuf};
#[derive(Debug, Default, PartialEq, Eq)]
pub(crate) struct Memory {
pub limit: Option<u64>,
pub headroom: Option<u64>,
}
#[derive(Debug)]
struct Domain {
mount: PathBuf,
current: PathBuf,
v2: bool,
}
pub(crate) fn pressure_files() -> Vec<PathBuf> {
visible_domains()
.into_iter()
.filter(|domain| domain.v2)
.flat_map(|domain| {
domain
.current
.ancestors()
.take_while(|path| path.starts_with(&domain.mount))
.map(|path| path.join("memory.pressure"))
.collect::<Vec<_>>()
})
.collect()
}
pub(crate) fn memory() -> Memory {
snapshot(&visible_domains())
}
fn visible_domains() -> Vec<Domain> {
let domains = std::fs::read_to_string("/proc/self/cgroup")
.ok()
.zip(std::fs::read_to_string("/proc/self/mountinfo").ok())
.map(|(groups, mounts)| domains(&groups, &mounts))
.unwrap_or_default();
if domains.is_empty() {
return vec![
Domain {
mount: "/sys/fs/cgroup".into(),
current: "/sys/fs/cgroup".into(),
v2: true,
},
Domain {
mount: "/sys/fs/cgroup/memory".into(),
current: "/sys/fs/cgroup/memory".into(),
v2: false,
},
];
}
domains
}
fn domains(groups: &str, mounts: &str) -> Vec<Domain> {
let memberships: Vec<_> = groups
.lines()
.filter_map(|line| {
let mut fields = line.splitn(3, ':');
fields.next()?;
let controllers = fields.next()?;
let path = Path::new(fields.next()?);
let v2 = controllers.is_empty();
(v2 || controllers.split(',').any(|name| name == "memory")).then_some((v2, path))
})
.collect();
mounts
.lines()
.filter_map(|line| {
let (left, right) = line.split_once(" - ")?;
let fields: Vec<_> = left.split_whitespace().collect();
let mut options = right.split_whitespace();
let fs = options.next()?;
options.next()?;
let super_options = options.next()?;
let v2 = match fs {
"cgroup2" => true,
"cgroup" if super_options.split(',').any(|name| name == "memory") => false,
_ => return None,
};
let root = mount_path(fields.get(3)?)?;
let mount = mount_path(fields.get(4)?)?;
let (_, member) = memberships
.iter()
.find(|(version, path)| *version == v2 && path.starts_with(&root))?;
if !safe_absolute(member) || !safe_absolute(&root) || !safe_absolute(&mount) {
return None;
}
let current = mount.join(member.strip_prefix(&root).ok()?);
Some(Domain { mount, current, v2 })
})
.collect()
}
fn safe_absolute(path: &Path) -> bool {
path.is_absolute() && !path.components().any(|c| matches!(c, Component::ParentDir))
}
fn mount_path(value: &str) -> Option<PathBuf> {
let mut bytes = Vec::new();
let mut input = value.as_bytes().iter().copied();
while let Some(byte) = input.next() {
if byte == b'\\' {
let mut decoded = 0u16;
for _ in 0..3 {
let digit = input.next()?;
if !(b'0'..=b'7').contains(&digit) {
return None;
}
decoded = decoded * 8 + u16::from(digit - b'0');
}
bytes.push(u8::try_from(decoded).ok()?);
} else {
bytes.push(byte);
}
}
Some(OsString::from_vec(bytes).into())
}
fn snapshot(domains: &[Domain]) -> Memory {
let mut result = Memory::default();
for domain in domains {
for directory in domain.current.ancestors() {
if !directory.starts_with(&domain.mount) {
break;
}
let (limit_name, usage_name, reclaim_field) = if domain.v2 {
("memory.max", "memory.current", "inactive_file")
} else {
(
"memory.limit_in_bytes",
"memory.usage_in_bytes",
"total_inactive_file",
)
};
let Some(limit) = std::fs::read_to_string(directory.join(limit_name))
.ok()
.and_then(|s| {
if s.trim() == "0" {
Some(0)
} else {
read_cgroup_text(&s)
}
})
else {
continue;
};
let usage = std::fs::read_to_string(directory.join(usage_name))
.ok()
.and_then(|s| s.trim().parse::<u64>().ok());
let reclaimable = std::fs::read_to_string(directory.join("memory.stat"))
.ok()
.and_then(|s| parse_cgroup_stat(&s, reclaim_field))
.unwrap_or(0);
let headroom = usage.map_or(limit, |used| {
limit.saturating_sub(used.saturating_sub(reclaimable))
});
result.limit = Some(result.limit.map_or(limit, |old| old.min(limit)));
result.headroom = Some(result.headroom.map_or(headroom, |old| old.min(headroom)));
}
}
result
}
#[cfg(test)]
mod tests {
use super::*;
fn write_memory(path: &Path, limit: &str, usage: u64, inactive: u64, v2: bool) {
std::fs::create_dir_all(path).unwrap();
let (limit_name, usage_name, field) = if v2 {
("memory.max", "memory.current", "inactive_file")
} else {
(
"memory.limit_in_bytes",
"memory.usage_in_bytes",
"total_inactive_file",
)
};
std::fs::write(path.join(limit_name), limit).unwrap();
std::fs::write(path.join(usage_name), usage.to_string()).unwrap();
std::fs::write(path.join("memory.stat"), format!("{field} {inactive}\n")).unwrap();
}
#[test]
fn nested_membership_uses_parent_headroom_including_siblings() {
let temp = tempfile::tempdir().unwrap();
let mount = temp.path();
write_memory(mount, "max", 0, 0, true);
write_memory(&mount.join("slice"), "1000", 950, 100, true);
write_memory(&mount.join("slice/build"), "800", 200, 50, true);
let mounts = format!("1 0 0:1 / {} rw - cgroup2 cgroup rw", mount.display());
let domains = domains("0::/slice/build\n", &mounts);
assert_eq!(
snapshot(&domains),
Memory {
limit: Some(800),
headroom: Some(150)
}
);
write_memory(&mount.join("slice"), "1000", 1100, 0, true);
assert_eq!(snapshot(&domains).headroom, Some(0));
}
#[test]
fn v1_memory_controller_and_subtree_mount() {
let temp = tempfile::tempdir().unwrap();
let mount = temp.path().join("memory mount");
write_memory(&mount, "1000", 950, 300, false);
write_memory(&mount.join("build"), "9223372036854771712", 100, 0, false);
let escaped = mount.to_string_lossy().replace(' ', "\\040");
let mounts = format!("1 0 0:1 /slice {escaped} rw - cgroup cgroup rw,memory\n");
let found = domains("2:cpu,cpuacct:/other\n3:memory:/slice/build\n", &mounts);
assert_eq!(found[0].current, mount.join("build"));
assert_eq!(
snapshot(&found),
Memory {
limit: Some(1000),
headroom: Some(350)
}
);
assert!(domains("3:memory:/slice-other/build", &mounts).is_empty());
}
#[test]
fn bind_mounts_do_not_hide_visible_ancestor_limits() {
let temp = tempfile::tempdir().unwrap();
let full = temp.path().join("full");
let bind = temp.path().join("bind");
write_memory(&full, "1000", 900, 0, true);
write_memory(&full.join("slice"), "max", 0, 0, true);
write_memory(&bind, "max", 0, 0, true);
let mounts = format!(
"1 0 0:1 /slice {} rw - cgroup2 cgroup rw\n2 0 0:1 / {} rw - cgroup2 cgroup rw",
bind.display(),
full.display()
);
assert_eq!(snapshot(&domains("0::/slice", &mounts)).headroom, Some(100));
}
#[test]
fn missing_stats_count_all_usage_and_zero_limit_is_real() {
let temp = tempfile::tempdir().unwrap();
write_memory(temp.path(), "1000", 700, 600, true);
let domains = [Domain {
mount: temp.path().into(),
current: temp.path().into(),
v2: true,
}];
std::fs::remove_file(temp.path().join("memory.stat")).unwrap();
assert_eq!(snapshot(&domains).headroom, Some(300));
std::fs::write(temp.path().join("memory.max"), "0").unwrap();
assert_eq!(
snapshot(&domains),
Memory {
limit: Some(0),
headroom: Some(0)
}
);
}
#[test]
fn malformed_mounts_and_escaping_memberships_are_ignored() {
let mounts = "broken\n1 0 0:1 / /sys/fs/cgroup rw - cgroup2 cgroup rw";
assert!(domains("0::/../escape", mounts).is_empty());
assert!(domains("0::relative", mounts).is_empty());
assert_eq!(mount_path("/a\\040b\\134c"), Some("/a b\\c".into()));
assert!(mount_path("/bad\\999").is_none());
}
}