lkml.org 
[lkml]   [2007]   [Jan]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH 9/9] net: vm deadlock avoidance core
    From
    Date
    On Tue, 2007-01-16 at 16:25 +0300, Evgeniy Polyakov wrote:
    > On Tue, Jan 16, 2007 at 10:46:06AM +0100, Peter Zijlstra (a.p.zijlstra@chello.nl) wrote:

    > > @@ -1767,10 +1767,23 @@ int netif_receive_skb(struct sk_buff *sk
    > > struct net_device *orig_dev;
    > > int ret = NET_RX_DROP;
    > > __be16 type;
    > > + unsigned long pflags = current->flags;
    > > +
    > > + /* Emergency skb are special, they should
    > > + * - be delivered to SOCK_VMIO sockets only
    > > + * - stay away from userspace
    > > + * - have bounded memory usage
    > > + *
    > > + * Use PF_MEMALLOC as a poor mans memory pool - the grouping kind.
    > > + * This saves us from propagating the allocation context down to all
    > > + * allocation sites.
    > > + */
    > > + if (unlikely(skb->emergency))
    > > + current->flags |= PF_MEMALLOC;
    >
    > Access to 'current' in netif_receive_skb()???
    > Why do you want to work with, for example keventd?

    Can this run in keventd?

    I thought this was softirq context and thus this would either run in a
    borrowed context or in ksoftirqd. See patch 3/9.

    > > @@ -1798,6 +1811,8 @@ int netif_receive_skb(struct sk_buff *sk
    > > goto ncls;
    > > }
    > > #endif
    > > + if (unlikely(skb->emergency))
    > > + goto skip_taps;
    > >
    > > list_for_each_entry_rcu(ptype, &ptype_all, list) {
    > > if (!ptype->dev || ptype->dev == skb->dev) {
    > > @@ -1807,6 +1822,7 @@ int netif_receive_skb(struct sk_buff *sk
    > > }
    > > }
    > >
    > > +skip_taps:
    >
    > It is still a 'tap'.

    Not sure what you are saying, I thought this should stop delivery of
    skbs to taps?

    > > #ifdef CONFIG_NET_CLS_ACT
    > > if (pt_prev) {
    > > ret = deliver_skb(skb, pt_prev, orig_dev);
    > > @@ -1819,15 +1835,26 @@ int netif_receive_skb(struct sk_buff *sk
    > >
    > > if (ret == TC_ACT_SHOT || (ret == TC_ACT_STOLEN)) {
    > > kfree_skb(skb);
    > > - goto out;
    > > + goto unlock;
    > > }
    > >
    > > skb->tc_verd = 0;
    > > ncls:
    > > #endif
    > >
    > > + if (unlikely(skb->emergency))
    > > + switch(skb->protocol) {
    > > + case __constant_htons(ETH_P_ARP):
    > > + case __constant_htons(ETH_P_IP):
    > > + case __constant_htons(ETH_P_IPV6):
    > > + break;
    >
    > Poor vlans and appletalk.

    Yeah and all those other too, maybe some day.

    > > Index: linux-2.6-git/net/ipv4/tcp_ipv4.c
    > > ===================================================================
    > > --- linux-2.6-git.orig/net/ipv4/tcp_ipv4.c 2007-01-12 12:20:07.000000000 +0100
    > > +++ linux-2.6-git/net/ipv4/tcp_ipv4.c 2007-01-12 12:21:14.000000000 +0100
    > > @@ -1604,6 +1604,22 @@ csum_err:
    > > goto discard;
    > > }
    > >
    > > +static int tcp_v4_backlog_rcv(struct sock *sk, struct sk_buff *skb)
    > > +{
    > > + int ret;
    > > + unsigned long pflags = current->flags;
    > > + if (unlikely(skb->emergency)) {
    > > + BUG_ON(!sk_has_vmio(sk)); /* we dropped those before queueing */
    > > + if (!(pflags & PF_MEMALLOC))
    > > + current->flags |= PF_MEMALLOC;
    > > + }
    > > +
    > > + ret = tcp_v4_do_rcv(sk, skb);
    > > +
    > > + current->flags = pflags;
    > > + return ret;
    >
    > Why don't you want to just setup PF_MEMALLOC for the socket and all
    > related processes?

    I'm not understanding what you're saying here.

    I want grant the processing of skb->emergency packets access to the
    memory reserves.

    How would I set PF_MEMALLOC on a socket, its a process flag? And which
    related processes?

    > > +}
    > > +
    > > /*
    > > * From tcp_input.c
    > > */
    > > @@ -1654,6 +1670,15 @@ int tcp_v4_rcv(struct sk_buff *skb)
    > > if (!sk)
    > > goto no_tcp_socket;
    > >
    > > + if (unlikely(skb->emergency)) {
    > > + if (!sk_has_vmio(sk))
    > > + goto discard_and_relse;
    > > + /*
    > > + decrease window size..
    > > + tcp_enter_quickack_mode(sk);
    > > + */
    >
    > How does this decrease window size?
    > Maybe ack scheduling would be better handled by inet_csk_schedule_ack()
    > or just directly send an ack, which in turn requires allocation, which
    > can be bound to this received frame processing...

    It doesn't, I thought that it might be a good idea doing that, but never
    got around to actually figuring out how to do it.

    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-01-16 15:19    [W:0.026 / U:0.612 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site