From: Alexei Starovoitov <ast@plumgrid•com>
To: Eric Dumazet <eric.dumazet@gmail•com>
Cc: "David S. Miller" <davem@davemloft•net>,
Eric Dumazet <edumazet@google•com>,
Daniel Borkmann <daniel@iogearbox•net>,
Thomas Graf <tgraf@suug•ch>, Jamal Hadi Salim <jhs@mojatatu•com>,
John Fastabend <john.r.fastabend@intel•com>,
netdev@vger•kernel.org
Subject: Re: [PATCH RFC net-next] pktgen: introduce 'rx' mode
Date: Wed, 29 Apr 2015 14:55:42 -0700 [thread overview]
Message-ID: <5541535E.1060908@plumgrid.com> (raw)
In-Reply-To: <1430280853.3711.19.camel@edumazet-glaptop2.roam.corp.google.com>
On 4/28/15 9:14 PM, Eric Dumazet wrote:
> On Tue, 2015-04-28 at 19:11 -0700, Alexei Starovoitov wrote:
>
>> + if (pkt_dev->flags & F_DO_RX) {
>> + local_bh_disable();
>> + atomic_add(burst, &pkt_dev->skb->users);
>> + do {
>> + ret = netif_receive_skb(pkt_dev->skb);
>> + if (ret == NET_RX_DROP)
>> + pkt_dev->errors++;
>> + pkt_dev->last_ok = 1;
>> + pkt_dev->sofar++;
>> + pkt_dev->seq_num++;
>> + } while (--burst > 0);
>> + local_bh_enable();
>> + goto out;
>> + }
>> +
>
> This looks buggy.
>
> skb can be put on a queue, so skb->next and skb->prev cannot be reused,
> or queues will be corrupted.
don't see the bug yet.
Any layer that wants to do such queueing should do skb_share_check
first. Just like ip_rcv does. So everything in IP world should
work fine, because it will be operating on clean cloned skb.
> Note that on TX, it is possible to have the same issue if you use a
> virtual device like bonding, and skb is queued on a slave qdisc.
>
> (Thats why we have this IFF_TX_SKB_SHARING flag)
yep, that's why xmit into veth is not useful for benchmarking of rx,
since the hottest functions are alloc_skb and fill_packet, while
netif_receive_skb is not even seen in top 10.
next prev parent reply other threads:[~2015-04-29 21:55 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-29 2:11 [PATCH RFC net-next] netif_receive_skb performance Alexei Starovoitov
2015-04-29 2:11 ` [PATCH RFC net-next] pktgen: introduce 'rx' mode Alexei Starovoitov
2015-04-29 4:14 ` Eric Dumazet
2015-04-29 21:55 ` Alexei Starovoitov [this message]
2015-04-29 22:19 ` Eric Dumazet
2015-04-29 22:38 ` Alexei Starovoitov
2015-04-29 22:56 ` Eric Dumazet
2015-04-29 23:28 ` Alexei Starovoitov
2015-04-29 23:39 ` Eric Dumazet
2015-04-29 23:59 ` Alexei Starovoitov
2015-04-29 5:23 ` [PATCH RFC net-next] netif_receive_skb performance Eric Dumazet
2015-04-29 22:15 ` Alexei Starovoitov
2015-04-29 9:37 ` Daniel Borkmann
2015-04-29 22:20 ` Alexei Starovoitov
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