Struct procfs::Io

pub struct Io {
    pub rchar: u64,
    pub wchar: u64,
    pub syscr: u64,
    pub syscw: u64,
    pub read_bytes: u64,
    pub write_bytes: u64,
    pub cancelled_write_bytes: u64,
}

This struct contains I/O statistics for the process, built from /proc/<pid>/io

To construct this structure, see Process::io().

Note

In the current implementation, things are a bit racy on 32-bit systems: if process A reads process B's /proc/<pid>/io while process B is updating one of these 64-bit counters, process A could see an intermediate result.

Fields

rchar: u64

Characters read

The number of bytes which this task has caused to be read from storage. This is simply the sum of bytes which this process passed to read(2) and similar system calls. It includes things such as terminal I/O and is unaffected by whether or not actual physical disk I/O was required (the read might have been satisfied from pagecache).

wchar: u64

characters written

The number of bytes which this task has caused, or shall cause to be written to disk. Similar caveats apply here as with rchar.

syscr: u64

read syscalls

Attempt to count the number of write I/O operations—that is, system calls such as write(2) and pwrite(2).

syscw: u64

write syscalls

Attempt to count the number of write I/O operations—that is, system calls such as write(2) and pwrite(2).

read_bytes: u64

bytes read

Attempt to count the number of bytes which this process really did cause to be fetched from the storage layer. This is accurate for block-backed filesystems.

write_bytes: u64

bytes written

Attempt to count the number of bytes which this process caused to be sent to the storage layer.

cancelled_write_bytes: u64

Cancelled write bytes.

The big inaccuracy here is truncate. If a process writes 1MB to a file and then deletes the file, it will in fact perform no write‐ out. But it will have been accounted as having caused 1MB of write. In other words: this field represents the number of bytes which this process caused to not happen, by truncating pagecache. A task can cause "negative" I/O too. If this task truncates some dirty pagecache, some I/O which another task has been accounted for (in its write_bytes) will not be happening.

Methods

impl Io

pub fn from_reader<R: Read>(r: R) -> Option<Io>

Trait Implementations

impl Debug for Io

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.