Re: [PATCH RFC] inetpeer: remove AVL implementation in favor of RB tree

On 05.07.2017 19:48, ericnetdev dumazet wrote:

On Jul 5, 2017 5:39 PM, "Mika Penttilä" <mika.penttila@nextfour.com <mailto:mika.penttila@nextfour.com>> wrote:

    Hi!


    On 05.07.2017 19:00, Eric Dumazet wrote:
    > From: Eric Dumazet <edumazet@google.com <mailto:edumazet@google.com>>
    >
    > As discussed in Faro during Netfilter Workshop 2017, RB trees can be
    > used with RCU, using a seqlock.
    >
    > Note that net/rxrpc/conn_service.c is already using this.
    >
    > This patch converts inetpeer from AVL tree to RB tree, since it allows
    > to remove private AVL code in favor of shared RB code.
    >
    > $ size net/ipv4/inetpeer.before net/ipv4/inetpeer.after
    >    text          data     bss     dec     hex filename
    >    3195            40     128    3363     d23 net/ipv4/inetpeer.before
    >    1562            24       0    1586     632 net/ipv4/inetpeer.after
    >
    > The same technique can be used to speed up
    > net/netfilter/nft_set_rbtree.c
    >
    > Signed-off-by: Eric Dumazet <edumazet@google.com <mailto:edumazet@google.com>>
    > ---
    >
    >       return p;
    > @@ -467,8 +231,9 @@ EXPORT_SYMBOL_GPL(inet_getpeer);
    >  void inet_putpeer(struct inet_peer *p)
    >  {
    >       p->dtime = (__u32)jiffies;
    > -     smp_mb__before_atomic();
    > -     refcount_dec(&p->refcnt);
    > +
    > +     if (refcount_dec_and_test(&p->refcnt))

    Missing rb_erase() here...



I am pretty sure it is not missing. Have you tested your suggestion ? Thanks !

Sorry I missed the fact the tree holds one reference.

    > +             call_rcu(&p->rcu, inetpeer_free_rcu);
    >  }
    >  EXPORT_SYMBOL_GPL(inet_putpeer);
    >
    >
    --Mika

Thanks,
Mika