Messages in this thread | | | Date | Thu, 15 Dec 2005 16:53:32 +1100 | From | Nick Piggin <> | Subject | Re: [RFC][PATCH 0/3] TCP/IP Critical socket communication mechanism |
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David S. Miller wrote: > From: Matt Mackall <mpm@selenic.com> > Date: Wed, 14 Dec 2005 21:02:50 -0800 > > >>There needs to be two rules: >> >>iff global memory critical flag is set >>- allocate from the global critical receive pool on receive >>- return packet to global pool if not destined for a socket with an >> attached send mempool > > > This shuts off a router and/or firewall just because iSCSI or NFS peed > in it's pants. Not really acceptable. >
But that should only happen (shut off a router and/or firewall) in cases where we now completely deadlock and never recover, including shutting off the router and firewall, because they don't have enough memory to recv packets either.
> >>I think this will provide the desired behavior > > > It's not desirable. > > What if iSCSI is protected by IPSEC, and the key management daemon has > to process a security assosciation expiration and negotiate a new one > in order for iSCSI to further communicate with it's peer when this > memory shortage occurs? It needs to send packets back and forth with > the remove key management daemon in order to do this, but since you > cut it off with this critical receive pool, the negotiation will never > succeed. >
I guess IPSEC would be a critical socket too, in that case. Sure there is nothing we can do if the daemon insists on allocating lots of memory...
> This stuff won't work. It's not a generic solution and that's > why it has more holes than swiss cheese. :-)
True it will have holes. I think something that is complementary and would be desirable is to simply limit the amount of in-flight writeout that things like NFS allows (or used to allow, haven't checked for a while and there were noises about it getting better).
-- SUSE Labs, Novell Inc.
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