> I'd rather read 2 bytes and mangle their bits around rather than
> having to, say, read 16 bytes to obtain the same amount of data.
> Unless, you can tell me that it's faster to just read the 16
> bytes.
Well, lets think about it for a minute... Cache loads happen
in terms of groups of bytes so reading a few more bytes is
not very low cost. Write gathering and write back means
that writing a few more bytes is also low cost. Instructions
to move data to and from memory can typically execute in
parallel on pipelined processors so moving a few more bytes
is also low cost again.
Now on the 6x86 at least bit shift operations are only
performed in the X pipeline, cause a pipeline stall, and
are relatively slow compared to memory loads and stores.
You can do a lot of memory loads and stores in the time
it takes to do a bit shift.
I think you might find that a 16 byte read is actually
faster than a 2 byte read and mangle...
Mike
-- .----------------------------------------------------------------------. | Mike Jagdis | Internet: mailto:mike@roan.co.uk | | Roan Technology Ltd. | | | 54A Peach Street, Wokingham | Telephone: +44 118 989 0403 | | RG40 1XG, ENGLAND | Fax: +44 118 989 1195 | `----------------------------------------------------------------------'
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu