From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [net-next RFC PATCH 4/7] tuntap: multiqueue support Date: Sun, 14 Aug 2011 02:05:25 -0400 (EDT) Message-ID: <1465655104.165911.1313301925197.JavaMail.root@zmail05.collab.prod.int.phx2.redhat.com> References: <1313159376.2354.26.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Cc: krkumar2@in.ibm.com, kvm@vger.kernel.org, mst@redhat.com, qemu-devel@nongnu.org, netdev@vger.kernel.org, rusty@rustcorp.com.au, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, mirq-linux@rere.qmqm.pl, davem@davemloft.net To: Eric Dumazet Return-path: In-Reply-To: <1313159376.2354.26.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org Sender: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org List-Id: netdev.vger.kernel.org ----- Original Message ----- > Le vendredi 12 ao=C3=BBt 2011 =C3=A0 09:55 +0800, Jason Wang a =C3=A9crit= : >=20 > >+ rxq =3D skb_get_rxhash(skb); > >+ if (rxq) { > >+ tfile =3D rcu_dereference(tun->tfiles[rxq % numqueues]); > >+ if (tfile) > >+ goto out; > >+ } >=20 > You can avoid an expensive divide with following trick : >=20 > u32 idx =3D ((u64)rxq * numqueues) >> 32; >=20 Sure. >=20 >=20 > > -static struct tun_struct *tun_get(struct file *file) > > +static void tun_detach_all(struct net_device *dev) > > { > > - return __tun_get(file->private_data); > > + struct tun_struct *tun =3D netdev_priv(dev); > > + struct tun_file *tfile, *tfile_list[MAX_TAP_QUEUES]; > > + int i, j =3D 0; > > + > > + spin_lock(&tun_lock); > > + > > + for (i =3D 0; i < MAX_TAP_QUEUES && tun->numqueues; i++) { > > + tfile =3D rcu_dereference_protected(tun->tfiles[i], > > + lockdep_is_held(&tun_lock)); > > + if (tfile) { > > + wake_up_all(&tfile->wq.wait); > > + tfile_list[i++] =3D tfile; >=20 > typo here, you want tfile_list[j++] =3D tfile; >=20 Yes, thanks for catching this. > > + rcu_assign_pointer(tun->tfiles[i], NULL); > > + rcu_assign_pointer(tfile->tun, NULL); > > + --tun->numqueues; > > + } > > + } > > + BUG_ON(tun->numqueues !=3D 0); > > + spin_unlock(&tun_lock); > > + > > + synchronize_rcu(); > > + for(--j; j >=3D 0; j--) > > + sock_put(&tfile_list[j]->sk); > > } > > >=20 > Could you take a look at net/packet/af_packet.c, to check how David > did > the whole fanout thing ? >=20 > __fanout_unlink() >=20 > Trick is to not leave NULL entries in the tun->tfiles[] array. >=20 > It makes things easier in hot path. Sure I would go to take a look at this. >=20 >=20 > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html