github.com/hbdrawn/golang@v0.0.0-20141214014649-6b835209aba2/src/runtime/debug.go (about)

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package runtime
     6  
     7  import "unsafe"
     8  
     9  // GOMAXPROCS sets the maximum number of CPUs that can be executing
    10  // simultaneously and returns the previous setting.  If n < 1, it does not
    11  // change the current setting.
    12  // The number of logical CPUs on the local machine can be queried with NumCPU.
    13  // This call will go away when the scheduler improves.
    14  func GOMAXPROCS(n int) int {
    15  	if n > _MaxGomaxprocs {
    16  		n = _MaxGomaxprocs
    17  	}
    18  	lock(&sched.lock)
    19  	ret := int(gomaxprocs)
    20  	unlock(&sched.lock)
    21  	if n <= 0 || n == ret {
    22  		return ret
    23  	}
    24  
    25  	semacquire(&worldsema, false)
    26  	gp := getg()
    27  	gp.m.gcing = 1
    28  	systemstack(stoptheworld)
    29  
    30  	// newprocs will be processed by starttheworld
    31  	newprocs = int32(n)
    32  
    33  	gp.m.gcing = 0
    34  	semrelease(&worldsema)
    35  	systemstack(starttheworld)
    36  	return ret
    37  }
    38  
    39  // NumCPU returns the number of logical CPUs on the local machine.
    40  func NumCPU() int {
    41  	return int(ncpu)
    42  }
    43  
    44  // NumCgoCall returns the number of cgo calls made by the current process.
    45  func NumCgoCall() int64 {
    46  	var n int64
    47  	for mp := (*m)(atomicloadp(unsafe.Pointer(&allm))); mp != nil; mp = mp.alllink {
    48  		n += int64(mp.ncgocall)
    49  	}
    50  	return n
    51  }
    52  
    53  // NumGoroutine returns the number of goroutines that currently exist.
    54  func NumGoroutine() int {
    55  	return int(gcount())
    56  }