github.com/m3db/m3@v1.5.0/src/x/sync/index_cpu.go (about)

     1  // Copyright (c) 2020 Uber Technologies, Inc.
     2  //
     3  // Permission is hereby granted, free of charge, to any person obtaining a copy
     4  // of this software and associated documentation files (the "Software"), to deal
     5  // in the Software without restriction, including without limitation the rights
     6  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     7  // copies of the Software, and to permit persons to whom the Software is
     8  // furnished to do so, subject to the following conditions:
     9  //
    10  // The above copyright notice and this permission notice shall be included in
    11  // all copies or substantial portions of the Software.
    12  //
    13  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    14  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    15  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    16  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    17  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    18  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    19  // THE SOFTWARE.
    20  
    21  package sync
    22  
    23  // CoreFn is a function that returns the ID of the
    24  // CPU currently running this goroutine.
    25  type CoreFn func() int
    26  
    27  var numCores = 1
    28  
    29  func init() {
    30  	numCores = checkNumCores()
    31  }
    32  
    33  // NumCores returns the number of cores returned from
    34  // OS-dependent checkNumCores(), if not available only returns 1
    35  func NumCores() int {
    36  	return numCores
    37  }
    38  
    39  // CPUCore returns the current CPU core.
    40  func CPUCore() int {
    41  	if numCores == 1 {
    42  		// Likely not linux and nothing available in procinfo meaning that
    43  		// even if RDTSCP is available we won't have setup correct number
    44  		// of cores, etc for our queues since we probed using NumCores
    45  		// and got 1 back.
    46  		return 0
    47  	}
    48  	// We know the number of cores, try to call RDTSCP to get the core.
    49  	return getCore()
    50  }