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Add std::thread::available_concurrency
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use crate::io; | ||
use crate::num::NonZeroUsize; | ||
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/// Returns the number of hardware threads available to the program. | ||
/// | ||
/// This value should be considered only a hint. | ||
/// | ||
/// # Platform-specific behavior | ||
/// | ||
/// If interpreted as the number of actual hardware threads, it may undercount on | ||
/// Windows systems with more than 64 hardware threads. If interpreted as the | ||
/// available concurrency for that process, it may overcount on Windows systems | ||
/// when limited by a process wide affinity mask or job object limitations, and | ||
/// it may overcount on Linux systems when limited by a process wide affinity | ||
/// mask or affected by cgroups limits. | ||
/// | ||
/// # Errors | ||
/// | ||
/// This function will return an error in the following situations, but is not | ||
/// limited to just these cases: | ||
/// | ||
/// - If the number of hardware threads is not known for the target platform. | ||
/// - The process lacks permissions to view the number of hardware threads | ||
/// available. | ||
/// | ||
/// # Examples | ||
/// | ||
/// ``` | ||
/// # #![allow(dead_code)] | ||
/// #![feature(available_concurrency)] | ||
/// use std::thread; | ||
/// | ||
/// let count = thread::available_concurrency().map(|n| n.get()).unwrap_or(1); | ||
/// ``` | ||
#[unstable(feature = "available_concurrency", issue = "74479")] | ||
pub fn available_concurrency() -> io::Result<NonZeroUsize> { | ||
available_concurrency_internal() | ||
} | ||
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cfg_if::cfg_if! { | ||
if #[cfg(windows)] { | ||
#[allow(nonstandard_style)] | ||
fn available_concurrency_internal() -> io::Result<NonZeroUsize> { | ||
#[repr(C)] | ||
struct SYSTEM_INFO { | ||
wProcessorArchitecture: u16, | ||
wReserved: u16, | ||
dwPageSize: u32, | ||
lpMinimumApplicationAddress: *mut u8, | ||
lpMaximumApplicationAddress: *mut u8, | ||
dwActiveProcessorMask: *mut u8, | ||
dwNumberOfProcessors: u32, | ||
dwProcessorType: u32, | ||
dwAllocationGranularity: u32, | ||
wProcessorLevel: u16, | ||
wProcessorRevision: u16, | ||
} | ||
extern "system" { | ||
fn GetSystemInfo(info: *mut SYSTEM_INFO) -> i32; | ||
} | ||
let res = unsafe { | ||
let mut sysinfo = crate::mem::zeroed(); | ||
GetSystemInfo(&mut sysinfo); | ||
sysinfo.dwNumberOfProcessors as usize | ||
}; | ||
match res { | ||
0 => Err(io::Error::new(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform")), | ||
cpus => Ok(unsafe { NonZeroUsize::new_unchecked(cpus) }), | ||
} | ||
} | ||
} else if #[cfg(any( | ||
target_os = "android", | ||
target_os = "cloudabi", | ||
target_os = "emscripten", | ||
target_os = "fuchsia", | ||
target_os = "ios", | ||
target_os = "linux", | ||
target_os = "macos", | ||
target_os = "solaris", | ||
target_os = "illumos", | ||
))] { | ||
fn available_concurrency_internal() -> io::Result<NonZeroUsize> { | ||
match unsafe { libc::sysconf(libc::_SC_NPROCESSORS_ONLN) } { | ||
-1 => Err(io::Error::last_os_error()), | ||
0 => Err(io::Error::new(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform")), | ||
cpus => Ok(unsafe { NonZeroUsize::new_unchecked(cpus as usize) }), | ||
} | ||
} | ||
} else if #[cfg(any(target_os = "freebsd", target_os = "dragonfly", target_os = "netbsd"))] { | ||
fn available_concurrency_internal() -> io::Result<NonZeroUsize> { | ||
use crate::ptr; | ||
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let mut cpus: libc::c_uint = 0; | ||
let mut cpus_size = crate::mem::size_of_val(&cpus); | ||
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unsafe { | ||
cpus = libc::sysconf(libc::_SC_NPROCESSORS_ONLN) as libc::c_uint; | ||
} | ||
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// Fallback approach in case of errors or no hardware threads. | ||
if cpus < 1 { | ||
let mut mib = [libc::CTL_HW, libc::HW_NCPU, 0, 0]; | ||
let res = unsafe { | ||
libc::sysctl( | ||
mib.as_mut_ptr(), | ||
2, | ||
&mut cpus as *mut _ as *mut _, | ||
&mut cpus_size as *mut _ as *mut _, | ||
ptr::null_mut(), | ||
0, | ||
) | ||
}; | ||
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// Handle errors if any. | ||
if res == -1 { | ||
return Err(io::Error::last_os_error()); | ||
} else if cpus == 0 { | ||
return Err(io::Error::new(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform")); | ||
} | ||
} | ||
Ok(unsafe { NonZeroUsize::new_unchecked(cpus as usize) }) | ||
} | ||
} else if #[cfg(target_os = "openbsd")] { | ||
fn available_concurrency_internal() -> io::Result<NonZeroUsize> { | ||
use crate::ptr; | ||
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let mut cpus: libc::c_uint = 0; | ||
let mut cpus_size = crate::mem::size_of_val(&cpus); | ||
let mut mib = [libc::CTL_HW, libc::HW_NCPU, 0, 0]; | ||
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let res = unsafe { | ||
libc::sysctl( | ||
mib.as_mut_ptr(), | ||
2, | ||
&mut cpus as *mut _ as *mut _, | ||
&mut cpus_size as *mut _ as *mut _, | ||
ptr::null_mut(), | ||
0, | ||
) | ||
}; | ||
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// Handle errors if any. | ||
if res == -1 { | ||
return Err(io::Error::last_os_error()); | ||
} else if cpus == 0 { | ||
return Err(io::Error::new(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform")); | ||
} | ||
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Ok(unsafe { NonZeroUsize::new_unchecked(cpus as usize) }) | ||
} | ||
} else { | ||
// FIXME: implement on vxWorks, Redox, HermitCore, Haiku, l4re | ||
fn available_concurrency_internal() -> io::Result<NonZeroUsize> { | ||
Err(io::Error::new(io::ErrorKind::NotFound, "The number of hardware threads is not known for the target platform")) | ||
} | ||
} | ||
} |
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