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      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