// Lock loads all memory pages in physical memory. This can take a long time for
// larger files but access to these memory locations will be faster.
func (m *Map) Lock() (err error) {
if err := syscall.Mlock(m.Data); err != nil {
return err
}
return nil
}
func main() {
flag.Parse()
allocationSize := *allocationInGB * GB
log.Printf("Allocating 0x%X bytes\n", allocationSize)
memory := make([]byte, allocationSize)
// mlock prevents memory from being swapped to disk
err := syscall.Mlock(memory)
if err != nil {
log.Fatalln("Error locking memory.", err)
}
var value byte
for {
log.Printf("Writing 0x%X to 0x%X bytes.\n", value, allocationSize)
for i, _ := range memory {
memory[i] = value
}
log.Printf("Verifying %x written to %x bytes.\n", value, allocationSize)
for i, v := range memory {
if v != value {
log.Printf("Found unexpected byte value 0x%X at position %d.\n", v, i)
}
}
value++
}
}
// Lock locks a region of the mapped shared memory
func (buf *sharedBuffer) Lock(offset, length int) error {
b := buf.Bytes()
err := checkOffsetLength(b, offset, length)
if err == nil {
err = syscall.Mlock(b[offset : offset+length])
}
return os.NewSyscallError("shm: mlock", err)
}
func mmapFile(fileName string) (*mmapData, error) {
file, err := os.Open(fileName)
if err != nil {
return nil, err
}
stat, err := file.Stat()
if err != nil {
file.Close()
return nil, err
}
size := stat.Size()
pageAlignedSize := (size + 4095) &^ 4095
data, err := syscall.Mmap(int(file.Fd()), 0, int(pageAlignedSize),
syscall.PROT_READ, syscall.MAP_PRIVATE)
if err != nil {
file.Close()
return nil, err
}
err = syscall.Mlock(data)
if err != nil {
syscall.Munmap(data)
file.Close()
return nil, err
}
md := &mmapData{file, data[:size]}
runtime.SetFinalizer(md, func(m *mmapData) {
syscall.Munlock(m.d)
syscall.Munmap(m.d)
m.f.Close()
})
return md, nil
}
// Lock implements Map.Lock().
func (m *mmap) Lock() error {
return syscall.Mlock(m.data)
}
// Prevent the mmap from being paged to the swap area.
func (m Mmap) Lock() error {
return syscall.Mlock(m)
}
