sled/
sys_limits.rs

1#![allow(unsafe_code)]
2
3#[cfg(any(target_os = "linux", target_os = "macos"))]
4use std::io;
5#[cfg(any(target_os = "linux"))]
6use {std::fs::File, std::io::Read};
7
8/// See the Kernel's documentation for more information about this subsystem,
9/// found at:  [Documentation/cgroup-v1/memory.txt](https://www.kernel.org/doc/Documentation/cgroup-v1/memory.txt)
10///
11/// If there's no memory limit specified on the container this may return
12/// 0x7FFFFFFFFFFFF000 (2^63-1 rounded down to 4k which is a common page size).
13/// So we know we are not running in a memory restricted environment.
14#[cfg(target_os = "linux")]
15fn get_cgroup_memory_limit() -> io::Result<u64> {
16    File::open("/sys/fs/cgroup/memory/memory.limit_in_bytes")
17        .and_then(read_u64_from)
18}
19
20#[cfg(target_os = "linux")]
21fn read_u64_from(mut file: File) -> io::Result<u64> {
22    let mut s = String::new();
23    file.read_to_string(&mut s).and_then(|_| {
24        s.trim()
25            .parse()
26            .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
27    })
28}
29
30/// Returns the maximum size of total available memory of the process, in bytes.
31/// If this limit is exceeded, the malloc() and mmap() functions shall fail with
32/// errno set to [ENOMEM].
33#[cfg(any(target_os = "linux", target_os = "macos"))]
34fn get_rlimit_as() -> io::Result<libc::rlimit> {
35    let mut limit = std::mem::MaybeUninit::<libc::rlimit>::uninit();
36
37    let ret = unsafe { libc::getrlimit(libc::RLIMIT_AS, limit.as_mut_ptr()) };
38
39    if ret == 0 {
40        Ok(unsafe { limit.assume_init() })
41    } else {
42        Err(io::Error::last_os_error())
43    }
44}
45
46#[cfg(any(target_os = "linux", target_os = "macos"))]
47pub fn get_available_memory() -> io::Result<u64> {
48    use std::convert::TryFrom;
49
50    let pages = unsafe { libc::sysconf(libc::_SC_PHYS_PAGES) };
51    if pages == -1 {
52        return Err(io::Error::last_os_error());
53    }
54
55    let page_size = unsafe { libc::sysconf(libc::_SC_PAGE_SIZE) };
56    if page_size == -1 {
57        return Err(io::Error::last_os_error());
58    }
59
60    Ok(u64::try_from(pages).unwrap() * u64::try_from(page_size).unwrap())
61}
62
63pub fn get_memory_limit() -> u64 {
64    // Maximum addressable memory space limit in u64
65    static MAX_USIZE: u64 = usize::max_value() as u64;
66
67    let mut max: u64 = 0;
68
69    #[cfg(target_os = "linux")]
70    {
71        if let Ok(mem) = get_cgroup_memory_limit() {
72            max = mem;
73        }
74
75        // If there's no memory limit specified on the container this
76        // actually returns 0x7FFFFFFFFFFFF000 (2^63-1 rounded down to
77        // 4k which is a common page size). So we know we are not
78        // running in a memory restricted environment.
79        // src: https://github.com/dotnet/coreclr/blob/master/src/pal/src/misc/cgroup.cpp#L385-L428
80        if max > 0x7FFF_FFFF_0000_0000 {
81            return 0;
82        }
83    }
84
85    #[cfg(any(target_os = "linux", target_os = "macos"))]
86    {
87        if let Ok(rlim) = get_rlimit_as() {
88            let rlim_cur = Into::<u64>::into(rlim.rlim_cur);
89            if rlim_cur < max || max == 0 {
90                max = rlim_cur;
91            }
92        }
93
94        if let Ok(available) = get_available_memory() {
95            if available < max || max == 0 {
96                max = available;
97            }
98        }
99    }
100
101    if max > MAX_USIZE {
102        // It is observed in practice when the memory is unrestricted, Linux
103        // control group returns a physical limit that is bigger than
104        // the address space
105        max = MAX_USIZE;
106    }
107
108    #[cfg(miri)]
109    {
110        // Miri has a significant memory consumption overhead. During a small
111        // test run, a memory amplification of ~35x was observed. Certain
112        // memory overheads may increase asymptotically with longer test runs,
113        // such as the interpreter's dead_alloc_map. Memory overhead is
114        // dominated by stacked borrows tags; the asymptotic behavior of this
115        // overhead needs further investigation.
116        max /= 40;
117    }
118
119    max
120}
sled/sys_limits.rs

sled/
sys_limits.rs
