Example #1
0
// mmap memory maps a DB's data file.
func mmap(db *DB, sz int) error {
	// Truncate and fsync to ensure file size metadata is flushed.
	// https://github.com/boltdb/bolt/issues/284
	if !db.NoGrowSync && !db.readOnly {
		if err := db.file.Truncate(int64(sz)); err != nil {
			return fmt.Errorf("file resize error: %s", err)
		}
		if err := db.file.Sync(); err != nil {
			return fmt.Errorf("file sync error: %s", err)
		}
	}

	// Map the data file to memory.
	b, err := unix.Mmap(int(db.file.Fd()), 0, sz, syscall.PROT_READ, syscall.MAP_SHARED)
	if err != nil {
		return err
	}

	// Advise the kernel that the mmap is accessed randomly.
	if err := unix.Madvise(b, syscall.MADV_RANDOM); err != nil {
		return fmt.Errorf("madvise: %s", err)
	}

	// Save the original byte slice and convert to a byte array pointer.
	db.dataref = b
	db.data = (*[maxMapSize]byte)(unsafe.Pointer(&b[0]))
	db.datasz = sz
	return nil
}
Example #2
0
func TestMmap(t *testing.T) {
	b, err := unix.Mmap(-1, 0, unix.Getpagesize(), unix.PROT_NONE, unix.MAP_ANON|unix.MAP_PRIVATE)
	if err != nil {
		t.Fatalf("Mmap: %v", err)
	}
	if err := unix.Munmap(b); err != nil {
		t.Fatalf("Munmap: %v", err)
	}
}