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//! Based on [heim's implementation](https://github.com/heim-rs/heim/blob/master/heim-disk/src/sys/linux/counters.rs).
use std::{
fs::File,
io::{self, BufRead, BufReader},
num::ParseIntError,
str::FromStr,
};
use crate::app::data_harvester::disks::IoCounters;
/// Copied from the `psutil` sources:
///
/// "man iostat" states that sectors are equivalent with blocks and have
/// a size of 512 bytes. Despite this value can be queried at runtime
/// via /sys/block/{DISK}/queue/hw_sector_size and results may vary
/// between 1k, 2k, or 4k... 512 appears to be a magic constant used
/// throughout Linux source code:
/// * <https://stackoverflow.com/a/38136179/376587>
/// * <https://lists.gt.net/linux/kernel/2241060>
/// * <https://github.com/giampaolo/psutil/issues/1305>
/// * <https://github.com/torvalds/linux/blob/4f671fe2f9523a1ea206f63fe60a7c7b3a56d5c7/include/linux/bio.h#L99>
/// * <https://lkml.org/lkml/2015/8/17/234>
const DISK_SECTOR_SIZE: u64 = 512;
impl FromStr for IoCounters {
type Err = anyhow::Error;
/// Converts a `&str` to an [`IoCounters`].
///
/// Follows the format used in Linux 2.6+. Note that this completely ignores the following stats:
/// - Discard stats from 4.18+
/// - Flush stats from 5.5+
///
/// <https://www.kernel.org/doc/Documentation/iostats.txt>
/// <https://www.kernel.org/doc/Documentation/ABI/testing/procfs-diskstats>
fn from_str(s: &str) -> anyhow::Result<IoCounters> {
fn next_part<'a>(iter: &mut impl Iterator<Item = &'a str>) -> Result<&'a str, io::Error> {
iter.next()
.ok_or_else(|| io::Error::from(io::ErrorKind::InvalidData))
}
fn next_part_to_u64<'a>(iter: &mut impl Iterator<Item = &'a str>) -> anyhow::Result<u64> {
next_part(iter)?
.parse()
.map_err(|err: ParseIntError| err.into())
}
// Skip the major and minor numbers.
let mut parts = s.split_whitespace().skip(2);
let name = next_part(&mut parts)?.to_string();
// Skip read count, read merged count.
let mut parts = parts.skip(2);
let read_bytes = next_part_to_u64(&mut parts)? * DISK_SECTOR_SIZE;
// Skip read time seconds, write count, and write merged count.
let mut parts = parts.skip(3);
let write_bytes = next_part_to_u64(&mut parts)? * DISK_SECTOR_SIZE;
Ok(IoCounters::new(name, read_bytes, write_bytes))
}
}
/// Returns an iterator of disk I/O stats. Pulls data from `/proc/diskstats`.
pub fn io_stats() -> anyhow::Result<Vec<IoCounters>> {
const PROC_DISKSTATS: &str = "/proc/diskstats";
let mut results = vec![];
let mut reader = BufReader::new(File::open(PROC_DISKSTATS)?);
let mut line = String::new();
// This saves us from doing a string allocation on each iteration compared to `lines()`.
while let Ok(bytes) = reader.read_line(&mut line) {
if bytes > 0 {
if let Ok(counters) = IoCounters::from_str(&line) {
results.push(counters);
}
line.clear();
} else {
break;
}
}
#[cfg(feature = "zfs")]
{
use crate::app::data_harvester::disks::zfs_io_counters;
if let Ok(mut zfs_io) = zfs_io_counters::zfs_io_stats() {
results.append(&mut zfs_io);
}
}
Ok(results)
}
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