bustd: Available memory or bust!bustd is a lightweight process killer daemon for out-of-memory scenarios for Linux!
bustd seems to use less memory than some other lean daemons such as earlyoom:
```console $ ps -F -C bustd UID PID PPID C SZ RSS PSR STIME TTY TIME CMD vrmiguel 353609 187407 5 151 8 2 01:20 pts/2 00:00:00 target/x86_64-unknown-linux-musl/release/bustd -V -n
$ ps -F -C earlyoom UID PID PPID C SZ RSS PSR STIME TTY TIME CMD vrmiguel 350497 9498 0 597 688 6 01:12 pts/1 00:00:00 ./earlyoom/ ```
¹: RSS stands for resident set size and represents the portion of RAM occupied by a process.
²: Compared when bustd was in this commit and earlyoom in this one.
bustd compiled with musl libc and earlyoom with glibc through GCC 11.1. Different configurations would likely change these figures.
Much like earlyoom and nohang, bustd uses adaptive sleep times during its memory polling. Unlike these two, however, bustd does not read from /proc/meminfo, instead opting for the sysinfo syscall.
This approach has its up- and downsides. The amount of free RAM that sysinfo reads does not account for cached memory, while MemAvailable in /proc/meminfo does.
The sysinfo syscall is one order of magnitude faster, at least according to this kernel patch (granted, from 2015).
As bustd can't solely rely on the free RAM readings of sysinfo, we check for memory stress through Pressure Stall Information.
bustd will try to lock all pages mapped into its address spaceMuch like earlyoom, bustd uses mlockall to avoid being sent to swap, which allows the daemon to remain responsive even when the system memory is under heavy load and susceptible to thrashing.
The Linux kernel, since version 4.20 (and built with CONFIG_PSI=y), presents canonical new pressure metrics for memory, CPU, and IO.
In the words of Facebook Incubator:
PSI stats are like barometers that provide fair warning of impending resource
shortages, enabling you to take more proactive, granular, and nuanced steps
when resources start becoming scarce.
More specifically, bustd checks for how long, in microseconds, processes have stalled in the last 10 seconds. By default, bustd will kill a process when processes have stalled for 25 microseconds in the last ten seconds.
Requirements:
* Rust toolchain
* Any C compiler
* Linux 4.20+ built with CONFIG_PSI=y
shell
git clone https://github.com/vrmiguel/bustd
cd bustd && cargo run --release
The -n, --no-daemon flag is useful for running bustd through an init system such as systemd.
Binaries are generated at every commit through GitHub Actions
bustd as a systemd service)bustd should never kill