cache_test.go

     1  // Copyright 2022 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 bcache
     6  
     7  import (
     8  	"fmt"
     9  	"runtime"
    10  	"sync"
    11  	"sync/atomic"
    12  	"testing"
    13  )
    14  
    15  var registeredCache Cache[int, int32]
    16  
    17  func init() {
    18  	registeredCache.Register()
    19  }
    20  
    21  var seq atomic.Uint32
    22  
    23  func next[T int | int32]() *T {
    24  	x := new(T)
    25  	*x = T(seq.Add(1))
    26  	return x
    27  }
    28  
    29  func str[T int | int32](x *T) string {
    30  	if x == nil {
    31  		return "nil"
    32  	}
    33  	return fmt.Sprint(*x)
    34  }
    35  
    36  func TestCache(t *testing.T) {
    37  	// Use unregistered cache for functionality tests,
    38  	// to keep the runtime from clearing behind our backs.
    39  	c := new(Cache[int, int32])
    40  
    41  	// Create many entries.
    42  	m := make(map[*int]*int32)
    43  	for i := 0; i < 10000; i++ {
    44  		k := next[int]()
    45  		v := next[int32]()
    46  		m[k] = v
    47  		c.Put(k, v)
    48  	}
    49  
    50  	// Overwrite a random 20% of those.
    51  	n := 0
    52  	for k := range m {
    53  		v := next[int32]()
    54  		m[k] = v
    55  		c.Put(k, v)
    56  		if n++; n >= 2000 {
    57  			break
    58  		}
    59  	}
    60  
    61  	// Check results.
    62  	for k, v := range m {
    63  		if cv := c.Get(k); cv != v {
    64  			t.Fatalf("c.Get(%v) = %v, want %v", str(k), str(cv), str(v))
    65  		}
    66  	}
    67  
    68  	c.Clear()
    69  	for k := range m {
    70  		if cv := c.Get(k); cv != nil {
    71  			t.Fatalf("after GC, c.Get(%v) = %v, want nil", str(k), str(cv))
    72  		}
    73  	}
    74  
    75  	// Check that registered cache is cleared at GC.
    76  	c = &registeredCache
    77  	for k, v := range m {
    78  		c.Put(k, v)
    79  	}
    80  	runtime.GC()
    81  	for k := range m {
    82  		if cv := c.Get(k); cv != nil {
    83  			t.Fatalf("after Clear, c.Get(%v) = %v, want nil", str(k), str(cv))
    84  		}
    85  	}
    86  
    87  	// Check that cache works for concurrent access.
    88  	// Lists are discarded if they reach 1000 entries,
    89  	// and there are cacheSize list heads, so we should be
    90  	// able to do 100 * cacheSize entries with no problem at all.
    91  	c = new(Cache[int, int32])
    92  	var barrier, wg sync.WaitGroup
    93  	const N = 100
    94  	barrier.Add(N)
    95  	wg.Add(N)
    96  	var lost int32
    97  	for i := 0; i < N; i++ {
    98  		go func() {
    99  			defer wg.Done()
   100  
   101  			m := make(map[*int]*int32)
   102  			for j := 0; j < cacheSize; j++ {
   103  				k, v := next[int](), next[int32]()
   104  				m[k] = v
   105  				c.Put(k, v)
   106  			}
   107  			barrier.Done()
   108  			barrier.Wait()
   109  
   110  			for k, v := range m {
   111  				if cv := c.Get(k); cv != v {
   112  					t.Errorf("c.Get(%v) = %v, want %v", str(k), str(cv), str(v))
   113  					atomic.AddInt32(&lost, +1)
   114  				}
   115  			}
   116  		}()
   117  	}
   118  	wg.Wait()
   119  	if lost != 0 {
   120  		t.Errorf("lost %d entries", lost)
   121  	}
   122  }
   123
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