add cache line example file

Author: web-flow

examples/cache-lines.go

@@ -0,0 +1,49 @@
+package main
+
+// Large struct that spans multiple cache lines (64 bytes each)
+type LargeStruct struct {
+	A  uint64   // 0-7   (cache line 0)
+	B  uint64   // 8-15  (cache line 0)
+	C  uint64   // 16-23 (cache line 0)
+	D  uint64   // 24-31 (cache line 0)
+	E  uint64   // 32-39 (cache line 0)
+	F  uint64   // 40-47 (cache line 0)
+	G  uint64   // 48-55 (cache line 0)
+	H  uint64   // 56-63 (cache line 0) - exactly fills line 0
+	I  uint64   // 64-71 (cache line 1)
+	J  uint64   // 72-79 (cache line 1)
+}
+
+// Struct with a field that crosses cache line boundary
+type CacheLineCrosser struct {
+	Padding [60]byte  // 0-59 (cache line 0)
+	Big     [16]byte  // 60-75 - CROSSES cache line 0→1!
+	After   uint64    // 80-87 (cache line 1)
+}
+
+// False sharing example - commonly accessed together but on different lines
+type FalseSharingRisk struct {
+	Counter1 uint64   // 0-7 (cache line 0) - hot field
+	Padding  [56]byte // 8-63 (fills cache line 0)
+	Counter2 uint64   // 64-71 (cache line 1) - hot field
+}
+
+// Well-aligned for concurrent access
+type CacheAligned struct {
+	Counter1 uint64   // cache line 0
+	_pad1    [56]byte // explicit padding to fill line
+	Counter2 uint64   // cache line 1
+	_pad2    [56]byte // explicit padding to fill line
+}
+
+// Typical struct that may cross cache lines unintentionally
+type HTTPRequest struct {
+	Method      string    // 0-15 (16 bytes)
+	URL         string    // 16-31 (16 bytes)
+	Headers     []byte    // 32-55 (24 bytes slice header)
+	Body        []byte    // 56-79 - CROSSES cache line!
+	ContentLen  int64     // 80-87
+	StatusCode  int32     // 88-91
+	IsSecure    bool      // 92
+	KeepAlive   bool      // 93
+}