> for non-i386 architectures. Once I thought I understood it and it seems
> related to cache line alignment. However, I am not sure exactly about the
> reason now. Can someone enlighten me a little bit?
A lot of pci net cards can only start packets on a 4 byte boundary. A lot
of CPU's need 4 byte aligned read/writes for performance. The ethernet header
is howerver 14 bytes long.
For CPU's with poor unaligned performance it turns out better to copy or
copy/checksum the data so the IP/TCP headers are aligned. If the card can
hit 16bit boundaries then you will see card drivers doing
alloc_skb(blah)
skb_reserve(skb, 2);
to align the header of he buffer so that the IP data is aligned
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
