client: tools: add helper to raise nofile rlimit

The default soft limit for open file handles is rather low, as some
apis (e.g. the POSIX `select(2)` syscall) do not work [0].

The lookahead cache use during the backup clients metadata comparison
to reuse unchanged files however requires much higher limits to work
effectively.

This helper function allows to raise the soft limit to the hard
limit, as provided by the `getrlimit(2)` syscall.

[0] https://0pointer.net/blog/file-descriptor-limits.html

Suggested-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
This commit is contained in:
Christian Ebner 2024-05-07 15:04:03 +02:00 committed by Fabian Grünbichler
parent 992487929a
commit 7b352cc0cf

View File

@ -612,3 +612,26 @@ pub fn handle_root_with_optional_format_version_prelude<R: pxar::decoder::SeqRea
_ => bail!("unexpected entry kind {:?}", first.kind()),
}
}
/// Raise the soft limit for open file handles to the hard limit
///
/// Returns the values set before raising the limit as libc::rlimit64
pub fn raise_nofile_limit() -> Result<libc::rlimit64, Error> {
let mut old = libc::rlimit64 {
rlim_cur: 0,
rlim_max: 0,
};
if 0 != unsafe { libc::getrlimit64(libc::RLIMIT_NOFILE, &mut old as *mut libc::rlimit64) } {
bail!("Failed to get nofile rlimit");
}
let mut new = libc::rlimit64 {
rlim_cur: old.rlim_max,
rlim_max: old.rlim_max,
};
if 0 != unsafe { libc::setrlimit64(libc::RLIMIT_NOFILE, &mut new as *mut libc::rlimit64) } {
bail!("Failed to set nofile rlimit");
}
Ok(old)
}