linux/procfs: add read_proc_stat
For now we just parse the CPU "time-spent" counters and calculate the
CPU usage of the whole system. As we do not want a total average we
use a state-full implementation, which calculates the usage since the
last request (if older than 1 second).
Somewhat modeled after our Perl version of this. But for the "total"
we do not use the:
> ($ctime - $last_proc_stat->{ctime}) * $clock_ticks * $cpucount;
calculation, but just add _all_ fields together, as that is the total
of CPU time.
Use a Reader-Writer lock to sync updating. First check under the
reader lock if the data is recent enough, else update it under the
writer lock.
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
This commit is contained in:
Thomas Lamprecht
parent
1e7467ee11
commit
cfae8ae3d2
@ -3,6 +3,8 @@ use std::fs::OpenOptions;
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use std::io::{BufRead, BufReader};
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use std::net::{Ipv4Addr, Ipv6Addr};
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use std::str::FromStr;
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use std::sync::RwLock;
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use std::time::Instant;
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use failure::*;
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use lazy_static::lazy_static;
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@ -164,6 +166,196 @@ pub fn read_proc_uptime_ticks() -> Result<(u64, u64), Error> {
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Ok((up as u64, idle as u64))
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}
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#[derive(Debug, Default)]
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/// The CPU fields from `/proc/stat` with their native time value. Multiply
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/// with CLOCK_TICKS to get the real value.
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pub struct ProcFsStat {
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/// Time spent in user mode.
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pub user: u64,
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/// Time spent in user mode with low priority (nice).
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pub nice: u64,
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/// Time spent in system mode.
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pub system: u64,
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/// Time spent in the idle task.
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pub idle: u64,
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/// Time waiting for I/O to complete. This value is not reiable, see `man 5 proc`
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pub iowait: u64,
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/// Time servicing interrupts.
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pub irq: u64,
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/// Time servicing softirqs.
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pub softirq: u64,
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/// Stolen time, which is the time spent in other operating systems when running
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/// in a virtualized environment.
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pub steal: u64,
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/// Time spent running a virtual CPU for guest operating systems under the control of the
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/// Linux kernel.
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pub guest: u64,
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/// Time spent running a niced guest (virtual CPU for guest operating systems under the control
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/// of the Linux kernel).
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pub guest_nice: u64,
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/// The sum of all other u64 fields
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pub total: u64,
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/// The percentage (0 - 1.0) of cpu utilization from the whole system, basica underlying calculation
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/// `1 - (idle / total)` but with delta values between now and the last call to `read_proc_stat` (min. 1s interval)
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pub cpu: f64,
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}
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lazy_static! {
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static ref PROC_LAST_STAT: RwLock<(ProcFsStat, Instant, bool)> =
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RwLock::new((ProcFsStat::default(), Instant::now(), true));
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}
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/// reads `/proc/stat`. For now only total host CPU usage is handled as the
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/// other metrics are not really interesting
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pub fn read_proc_stat() -> Result<ProcFsStat, Error> {
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let sample_time = Instant::now();
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let mut stat =
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parse_proc_stat(unsafe { std::str::from_utf8_unchecked(&std::fs::read("/proc/stat")?) })
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.unwrap();
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{
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// read lock scope
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let prev_read_guarded = PROC_LAST_STAT.read().unwrap();
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let (prev_stat, prev_time, first_time) = &*prev_read_guarded;
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let last_update = sample_time
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.saturating_duration_since(*prev_time)
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.as_millis();
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// only update if data is old
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if last_update < 1000 && !first_time {
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stat.cpu = prev_stat.cpu;
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return Ok(stat);
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}
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}
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{
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// write lock scope
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let mut prev_write_guarded = PROC_LAST_STAT.write().unwrap();
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// we do not expect much lock contention, so sample_time should be
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// recent. Else, we'd need to reread & parse here to get current data
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let (prev_stat, prev_time, first_time) = &mut *prev_write_guarded;
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let delta_total = stat.total - prev_stat.total;
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let delta_idle = stat.idle - prev_stat.idle;
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stat.cpu = 1. - (delta_idle as f64) / (delta_total as f64);
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*prev_stat = ProcFsStat { ..stat };
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*prev_time = sample_time;
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*first_time = false;
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}
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Ok(stat)
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}
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fn parse_proc_stat(statstr: &str) -> Result<ProcFsStat, Error> {
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// for now we just use the first accumulated "cpu" line
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let mut parts = statstr.trim_start().split_ascii_whitespace();
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parts.next(); // swallow initial cpu string
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// helpers:
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fn required<'a>(value: Option<&'a str>, what: &'static str) -> Result<&'a str, Error> {
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value.ok_or_else(|| format_err!("missing '{}' in /proc/stat", what))
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}
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fn req_num<T>(value: Option<&str>, what: &'static str) -> Result<T, Error>
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where
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T: FromStr,
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<T as FromStr>::Err: std::fmt::Display,
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{
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required(value, what)?
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.parse::<T>()
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.map_err(|e| format_err!("error parsing {}: {}", what, e))
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}
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let mut stat = ProcFsStat {
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user: req_num::<u64>(parts.next(), "user")?,
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nice: req_num::<u64>(parts.next(), "nice")?,
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system: req_num::<u64>(parts.next(), "system")?,
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idle: req_num::<u64>(parts.next(), "idle")?,
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iowait: req_num::<u64>(parts.next(), "iowait")?,
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irq: req_num::<u64>(parts.next(), "irq")?,
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softirq: req_num::<u64>(parts.next(), "softirq")?,
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steal: req_num::<u64>(parts.next(), "steal")?,
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guest: req_num::<u64>(parts.next(), "guest")?,
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guest_nice: req_num::<u64>(parts.next(), "guest_nice")?,
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total: 0,
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cpu: 0.0,
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};
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stat.total = stat.user
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+ stat.nice
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+ stat.system
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+ stat.iowait
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+ stat.irq
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+ stat.softirq
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+ stat.steal
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+ stat.guest
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+ stat.guest_nice
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+ stat.idle;
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// returns avg. heuristic for the first request
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stat.cpu = 1. - (stat.idle as f64) / (stat.total as f64);
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Ok(stat)
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}
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#[test]
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fn test_read_proc_stat() {
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let stat = parse_proc_stat(
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"cpu 2845612 241 173179 264715515 93366 0 7925 141017 0 0\n\
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cpu0 174375 9 11367 16548335 5741 0 2394 8500 0 0\n\
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cpu1 183367 11 11423 16540656 4644 0 1235 8888 0 0\n\
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cpu2 179636 21 20463 16534540 4802 0 456 9270 0 0\n\
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cpu3 184560 9 11379 16532136 7113 0 225 8967 0 0\n\
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cpu4 182341 17 10277 16542865 3274 0 181 8461 0 0\n\
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cpu5 179771 22 9910 16548859 2259 0 112 8328 0 0\n\
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cpu6 181185 14 8933 16548550 2057 0 78 8313 0 0\n\
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cpu7 176326 12 8514 16553428 2246 0 76 8812 0 0\n\
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cpu8 177341 13 7942 16553880 1576 0 56 8565 0 0\n\
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cpu9 176883 10 8648 16547886 3067 0 103 8788 0 0\n\
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cpu10 169446 4 7993 16561700 1584 0 39 8797 0 0\n\
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cpu11 170878 7 7783 16560870 1526 0 23 8444 0 0\n\
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cpu12 164062 12 7839 16567155 1686 0 43 8794 0 0\n\
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cpu13 164303 4 7661 16567497 1528 0 41 8525 0 0\n\
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cpu14 173709 2 11478 16546352 3965 0 571 9414 0 0\n\
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cpu15 207422 67 21561 16460798 46292 0 2283 10142 0 0\n\
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intr 29200426 1 9 0 0 0 0 3 0 1 0 275744 40 16 0 0 166292 0 0 0 0 0 0 0 0 0 0 \
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0 1463843 0 1048751 328317 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 \
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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 \
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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 \
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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 \
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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 \
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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 \
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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 \
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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 \
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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 \
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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 \
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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 \
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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 \
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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 \
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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0\n\
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ctxt 27543372\n\
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btime 1576502436\n\
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processes 701089\n\
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procs_running 2\n\
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procs_blocked 0\n\
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softirq 36227960 0 16653965 39 1305264 1500573 0 38330 5024204 356 11705229",
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)
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.expect("successful parsed a sample /proc/stat entry");
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assert_eq!(stat.user, 2845612);
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assert_eq!(stat.nice, 241);
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assert_eq!(stat.system, 173179);
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assert_eq!(stat.idle, 264715515);
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assert_eq!(stat.iowait, 93366);
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assert_eq!(stat.irq, 0);
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assert_eq!(stat.softirq, 7925);
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assert_eq!(stat.steal, 141017);
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assert_eq!(stat.guest, 0);
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assert_eq!(stat.guest_nice, 0);
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assert_eq!(stat.total, 267976855);
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assert_eq!(stat.cpu, 0.012170230149167183);
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}
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#[derive(Debug)]
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pub struct ProcFsMemInfo {
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pub memtotal: u64,
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