github.com/puzpuzpuz/xsync/v3@v3.1.1-0.20240225193106-cbe4ec1e954f/util.go (about)

     1  package xsync
     2  
     3  import (
     4  	"runtime"
     5  	_ "unsafe"
     6  )
     7  
     8  // test-only assert()-like flag
     9  var assertionsEnabled = false
    10  
    11  const (
    12  	// cacheLineSize is used in paddings to prevent false sharing;
    13  	// 64B are used instead of 128B as a compromise between
    14  	// memory footprint and performance; 128B usage may give ~30%
    15  	// improvement on NUMA machines.
    16  	cacheLineSize = 64
    17  )
    18  
    19  // nextPowOf2 computes the next highest power of 2 of 32-bit v.
    20  // Source: https://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
    21  func nextPowOf2(v uint32) uint32 {
    22  	if v == 0 {
    23  		return 1
    24  	}
    25  	v--
    26  	v |= v >> 1
    27  	v |= v >> 2
    28  	v |= v >> 4
    29  	v |= v >> 8
    30  	v |= v >> 16
    31  	v++
    32  	return v
    33  }
    34  
    35  func parallelism() uint32 {
    36  	maxProcs := uint32(runtime.GOMAXPROCS(0))
    37  	numCores := uint32(runtime.NumCPU())
    38  	if maxProcs < numCores {
    39  		return maxProcs
    40  	}
    41  	return numCores
    42  }
    43  
    44  //go:noescape
    45  //go:linkname runtime_fastrand runtime.fastrand
    46  func runtime_fastrand() uint32