On Wed, Feb 28, 2001 at 09:21:24PM -0500, Jeff Garzik wrote: > Instead of unconditionally copying packet sizes over rx_copybreak, in > many ethernet drivers... is it worth it for the driver to check and see > if the packet is already aligned? Or is that such a rare case that it > shouldn't be worth it? To know if packet is aligned or not, one must look into the packet to analyze protocols. IMO it is far better to setup the card to do RX DMA into DIX aligned IP frame (the most common case), but hardware which is inherently unable to do that has drivers knowing it. My nonexhaustive list of cards says: - Tulip: RX DMA alignment: 4 bytes (buffer sizes have same alignment, one can't do tricks like receive 12 bytes to the first buffer, rest to the next) - 3c59x: RX DMA alignment: 1 byte (all 3c90X cards) - eepro100: RX DMA alignment: unknown ! (for lack of certain part of intel documents) > Jeff > -- > Jeff Garzik | "You see, in this world there's two kinds of > Building 1024 | people, my friend: Those with loaded guns > MandrakeSoft | and those who dig. You dig." --Blondie /Matti Aarnio - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org
