> The code below consumes ~40% of the total execution time. According to
the profiler i := uint64(arg.(uint32)) is a major contributor
>
> // Cast the integer argument to uint64 and call a "writer"
> // The "writer" knows how many bytes to add to the binary stream
> // Type casts from interface{} to integer consume 40% of the overall
> // time. Can I do better? What is interface{} in Golang?
> func (b *Binlog) writeArgumentToOutput(writer writer, arg interface{},
argKind reflect.Kind) error {
> // unsafe pointer to the data depends on the data type
> var err error
> switch argKind {
> case reflect.Int8:
> i := uint64(arg.(int8))
> err = writer.write(b.ioWriter, unsafe.Pointer(&i))
> case reflect.Int16:
> i := uint64(arg.(int16))
> err = writer.write(b.ioWriter, unsafe.Pointer(&i))
> case reflect.Int32:
> i := uint64(arg.(int32))
> err = writer.write(b.ioWriter, unsafe.Pointer(&i))
> case reflect.Int64:
> i := uint64(arg.(int64))
> err = writer.write(b.ioWriter, unsafe.Pointer(&i))
> case reflect.Uint8:
> i := uint64(arg.(uint8))
> err = writer.write(b.ioWriter, unsafe.Pointer(&i))
> case reflect.Uint16:
> i := uint64(arg.(uint16))
> err = writer.write(b.ioWriter, unsafe.Pointer(&i))
> case reflect.Uint32:
> i := uint64(arg.(uint32))
> err = writer.write(b.ioWriter, unsafe.Pointer(&i))
> case reflect.Uint64:
> i := uint64(arg.(uint64))
> err = writer.write(b.ioWriter, unsafe.Pointer(&i))
> case reflect.Int:
> i := uint64(arg.(int))
> err = writer.write(b.ioWriter, unsafe.Pointer(&i))
> case reflect.Uint:
> i := uint64(arg.(uint))
> err = writer.write(b.ioWriter, unsafe.Pointer(&i))
> default:
> return fmt.Errorf("Unsupported type: %T\n",
reflect.TypeOf(arg))
> }
> return err
> }
What roger peppe said.
- Performing an unchecked type assertion is incorrect in the general case.
Example: https://play.golang.org/p/YmZyw0MnOK8
- Unsafe seems to be used for no good reason.
- Reflect ditto.
This code https://play.golang.org/p/4sd1yayjoNY prints
50000000 35.3 ns/op
While this one https://play.golang.org/p/tSfWbrqv4PN prints
100000000 18.7 ns/op
Using Intel® Xeon(R) CPU E5-1650 v2 @ 3.50GHz × 12.
PS: The last two links point to code that cannot run in the playground.
--
-j
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