Hi!
...
quoted
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.
Some of your users are developers, too :-). Should I generate a patch?
quoted
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.
Hmm, ok, it is not as simple as I thought. include/linux/netpoll.h
already includes mechanism to notify interested parties really soon,
but drivers still call dev_alloc_skb() before that.
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.
Hmm, adding GFP_GIVE_ME_EMERGENCY_POOLS to dev_alloc_skb(), then doing
...
int netif_rx(struct sk_buff *skb)
{
struct softnet_data *queue;
unsigned long flags;
/* if netpoll wants it, pretend we never saw it */
if (netpoll_rx(skb))
return NET_RX_DROP;
if (memory_is_still_very_low())
return NET_RX_DROP;
...should do the trick. Would something like that be acceptable to
network people?
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html