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SubjectRe: [PATCH 0/9] VM deadlock avoidance -v10
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On Wed, 2007-01-17 at 10:12 +0100, Pavel Machek wrote:
> Hi!
>
> > These patches implement the basic infrastructure to allow swap over networked
> > storage.
> >
> > The basic idea is to reserve some memory up front to use when regular memory
> > runs out.
> >
> > To bound network behaviour we accept only a limited number of concurrent
> > packets and drop those packets that are not aimed at the connection(s) servicing
> > the VM. Also all network paths that interact with userspace are to be avoided -
> > e.g. taps and NF_QUEUE.
> >
> > PF_MEMALLOC is set when processing emergency skbs. This makes sense in that we
> > are indeed working on behalf of the swapper/VM. This allows us to use the
> > regular memory allocators for processing but requires that said processing have
> > bounded memory usage and has that accounted in the reserve.
>
> How does it work with ARP, for example? You still need to reply to ARP
> if you want to keep your ethernet connections.

ETH_P_ARP is fully processed (under PF_MEMALLOC).

ETH_P_IP{,V6} starts to drop packets not for selected sockets
(SOCK_VMIO) and processes the rest (under PF_MEMALLOC) with limitations;
the packet may never depend on user-space to complete processing.

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