select2.go

     1  // run
     2  
     3  // Copyright 2010 The Go Authors. All rights reserved.
     4  // Use of this source code is governed by a BSD-style
     5  // license that can be found in the LICENSE file.
     6  
     7  // Test that selects do not consume undue memory.
     8  
     9  package main
    10  
    11  import "runtime"
    12  
    13  func sender(c chan int, n int) {
    14  	for i := 0; i < n; i++ {
    15  		c <- 1
    16  	}
    17  }
    18  
    19  func receiver(c, dummy chan int, n int) {
    20  	for i := 0; i < n; i++ {
    21  		select {
    22  		case <-c:
    23  			// nothing
    24  		case <-dummy:
    25  			panic("dummy")
    26  		}
    27  	}
    28  }
    29  
    30  func main() {
    31  	runtime.MemProfileRate = 0
    32  
    33  	c := make(chan int)
    34  	dummy := make(chan int)
    35  
    36  	// warm up
    37  	go sender(c, 100000)
    38  	receiver(c, dummy, 100000)
    39  	runtime.GC()
    40  	memstats := new(runtime.MemStats)
    41  	runtime.ReadMemStats(memstats)
    42  	alloc := memstats.Alloc
    43  
    44  	// second time shouldn't increase footprint by much
    45  	go sender(c, 100000)
    46  	receiver(c, dummy, 100000)
    47  	runtime.GC()
    48  	runtime.ReadMemStats(memstats)
    49  
    50  	// Be careful to avoid wraparound.
    51  	if memstats.Alloc > alloc && memstats.Alloc-alloc > 1.1e5 {
    52  		println("BUG: too much memory for 100,000 selects:", memstats.Alloc-alloc)
    53  	}
    54  }
    55
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