|
| 1 | +use crate::io; |
| 2 | +use crate::num::NonZeroUsize; |
| 3 | + |
| 4 | +/// Returns the number of hardware threads available to the program. |
| 5 | +/// |
| 6 | +/// This value should be considered only a hint. |
| 7 | +/// |
| 8 | +/// # Platform-specific behavior |
| 9 | +/// |
| 10 | +/// If interpreted as the number of actual hardware threads, it may undercount on |
| 11 | +/// Windows systems with more than 64 hardware threads. If interpreted as the |
| 12 | +/// available concurrency for that process, it may overcount on Windows systems |
| 13 | +/// when limited by a process wide affinity mask or job object limitations, and |
| 14 | +/// it may overcount on Linux systems when limited by a process wide affinity |
| 15 | +/// mask or affected by cgroups limits. |
| 16 | +/// |
| 17 | +/// # Errors |
| 18 | +/// |
| 19 | +/// This function will return an error in the following situations, but is not |
| 20 | +/// limited to just these cases: |
| 21 | +/// |
| 22 | +/// - If the number of hardware threads is not known for the target platform. |
| 23 | +/// - The process lacks permissions to view the number of hardware threads |
| 24 | +/// available. |
| 25 | +/// |
| 26 | +/// # Examples |
| 27 | +/// |
| 28 | +/// ``` |
| 29 | +/// # #![allow(dead_code)] |
| 30 | +/// #![feature(available_concurrency)] |
| 31 | +/// use std::thread; |
| 32 | +/// |
| 33 | +/// let count = thread::available_concurrency().map(|n| n.get()).unwrap_or(1); |
| 34 | +/// ``` |
| 35 | +#[unstable(feature = "available_concurrency", issue = "74479")] |
| 36 | +pub fn available_concurrency() -> io::Result<NonZeroUsize> { |
| 37 | + available_concurrency_internal() |
| 38 | +} |
| 39 | + |
| 40 | +cfg_if::cfg_if! { |
| 41 | + if #[cfg(windows)] { |
| 42 | + #[allow(nonstandard_style)] |
| 43 | + fn available_concurrency_internal() -> io::Result<NonZeroUsize> { |
| 44 | + #[repr(C)] |
| 45 | + struct SYSTEM_INFO { |
| 46 | + wProcessorArchitecture: u16, |
| 47 | + wReserved: u16, |
| 48 | + dwPageSize: u32, |
| 49 | + lpMinimumApplicationAddress: *mut u8, |
| 50 | + lpMaximumApplicationAddress: *mut u8, |
| 51 | + dwActiveProcessorMask: *mut u8, |
| 52 | + dwNumberOfProcessors: u32, |
| 53 | + dwProcessorType: u32, |
| 54 | + dwAllocationGranularity: u32, |
| 55 | + wProcessorLevel: u16, |
| 56 | + wProcessorRevision: u16, |
| 57 | + } |
| 58 | + extern "system" { |
| 59 | + fn GetSystemInfo(info: *mut SYSTEM_INFO) -> i32; |
| 60 | + } |
| 61 | + let res = unsafe { |
| 62 | + let mut sysinfo = crate::mem::zeroed(); |
| 63 | + GetSystemInfo(&mut sysinfo); |
| 64 | + sysinfo.dwNumberOfProcessors as usize |
| 65 | + }; |
| 66 | + match res { |
| 67 | + 0 => Err(io::Error::new(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform")), |
| 68 | + cpus => Ok(unsafe { NonZeroUsize::new_unchecked(cpus) }), |
| 69 | + } |
| 70 | + } |
| 71 | + } else if #[cfg(any( |
| 72 | + target_os = "android", |
| 73 | + target_os = "cloudabi", |
| 74 | + target_os = "emscripten", |
| 75 | + target_os = "fuchsia", |
| 76 | + target_os = "ios", |
| 77 | + target_os = "linux", |
| 78 | + target_os = "macos", |
| 79 | + target_os = "solaris", |
| 80 | + target_os = "illumos", |
| 81 | + ))] { |
| 82 | + fn available_concurrency_internal() -> io::Result<NonZeroUsize> { |
| 83 | + match unsafe { libc::sysconf(libc::_SC_NPROCESSORS_ONLN) } { |
| 84 | + -1 => Err(io::Error::last_os_error()), |
| 85 | + 0 => Err(io::Error::new(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform")), |
| 86 | + cpus => Ok(unsafe { NonZeroUsize::new_unchecked(cpus as usize) }), |
| 87 | + } |
| 88 | + } |
| 89 | + } else if #[cfg(any(target_os = "freebsd", target_os = "dragonfly", target_os = "netbsd"))] { |
| 90 | + fn available_concurrency_internal() -> io::Result<NonZeroUsize> { |
| 91 | + use crate::ptr; |
| 92 | + |
| 93 | + let mut cpus: libc::c_uint = 0; |
| 94 | + let mut cpus_size = crate::mem::size_of_val(&cpus); |
| 95 | + |
| 96 | + unsafe { |
| 97 | + cpus = libc::sysconf(libc::_SC_NPROCESSORS_ONLN) as libc::c_uint; |
| 98 | + } |
| 99 | + |
| 100 | + // Fallback approach in case of errors or no hardware threads. |
| 101 | + if cpus < 1 { |
| 102 | + let mut mib = [libc::CTL_HW, libc::HW_NCPU, 0, 0]; |
| 103 | + let res = unsafe { |
| 104 | + libc::sysctl( |
| 105 | + mib.as_mut_ptr(), |
| 106 | + 2, |
| 107 | + &mut cpus as *mut _ as *mut _, |
| 108 | + &mut cpus_size as *mut _ as *mut _, |
| 109 | + ptr::null_mut(), |
| 110 | + 0, |
| 111 | + ) |
| 112 | + }; |
| 113 | + |
| 114 | + // Handle errors if any. |
| 115 | + if res == -1 { |
| 116 | + return Err(io::Error::last_os_error()); |
| 117 | + } else if cpus == 0 { |
| 118 | + return Err(io::Error::new(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform")); |
| 119 | + } |
| 120 | + } |
| 121 | + Ok(unsafe { NonZeroUsize::new_unchecked(cpus as usize) }) |
| 122 | + } |
| 123 | + } else if #[cfg(target_os = "openbsd")] { |
| 124 | + fn available_concurrency_internal() -> io::Result<NonZeroUsize> { |
| 125 | + use crate::ptr; |
| 126 | + |
| 127 | + let mut cpus: libc::c_uint = 0; |
| 128 | + let mut cpus_size = crate::mem::size_of_val(&cpus); |
| 129 | + let mut mib = [libc::CTL_HW, libc::HW_NCPU, 0, 0]; |
| 130 | + |
| 131 | + let res = unsafe { |
| 132 | + libc::sysctl( |
| 133 | + mib.as_mut_ptr(), |
| 134 | + 2, |
| 135 | + &mut cpus as *mut _ as *mut _, |
| 136 | + &mut cpus_size as *mut _ as *mut _, |
| 137 | + ptr::null_mut(), |
| 138 | + 0, |
| 139 | + ) |
| 140 | + }; |
| 141 | + |
| 142 | + // Handle errors if any. |
| 143 | + if res == -1 { |
| 144 | + return Err(io::Error::last_os_error()); |
| 145 | + } else if cpus == 0 { |
| 146 | + return Err(io::Error::new(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform")); |
| 147 | + } |
| 148 | + |
| 149 | + Ok(unsafe { NonZeroUsize::new_unchecked(cpus as usize) }) |
| 150 | + } |
| 151 | + } else { |
| 152 | + // FIXME: implement on vxWorks, Redox, HermitCore, Haiku, l4re |
| 153 | + fn available_concurrency_internal() -> io::Result<NonZeroUsize> { |
| 154 | + Err(io::Error::new(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform")) |
| 155 | + } |
| 156 | + } |
| 157 | +} |
0 commit comments