On Tue, Jul 31, 2007 at 05:29:24PM +0200, Pavel Machek wrote: ... > Is the protocol documented somewhere? aoe.txt only points at > HOWTO... aha, protocol is linked from wikipedia. > http://www.coraid.com/documents/AoEr10.txt ... perhaps that should be > linked from aoe.txt, too?
Perhaps. Most people reading the aoe.txt file won't need to refer to the protocol itself, though. > Hmm, aoe protocol is really trivial. Perhaps netpoll/netconsole > infrastructure could be used to create driver good enough for > swapping? (Ok, it would not neccessarily perform too well, but... we'd > simply wait for the reply synchronously. It should be pretty simple). I think that in general you still need a way to receive write confirmations without allocating memory, and the driver can't provide that mechanism. The problem is that when memory is scarce, writes of dirty data must be able to complete, but because memory is scarce, there might not be enough to receive and process packets write-reponse packets, and the driver has no way of affecting the situation. That's why I think a callback could work: The network layer could allow storage drivers to register a callback that recognizes write responses. Usually the callback would not be used, but if free pages became so scarce that network receives could not take place in a normal fashion, the (zero or few) registered callbacks would be used to quickly determine whether each packet was a write response. The distinction is important, because write responses can result in the freeing of pages. When a storage driver's callback identified a write response, then a reserved skb could be used to process the receive without allocating memory. During the memory crunch packets that were not write responses would be dropped just as they are already, but dirty pages would be flushed. The mechanism would only take effect when free pages were scarce. It is easy to chat, though. Maybe someday I will test and submit a patch that implements this mechanism, but I'm hoping that somebody beats me to it. :) -- Ed L Cashin <[EMAIL PROTECTED]> - 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/
