From: "Toke Høiland-Jørgensen" <toke@redhat•com>
To: Hangbin Liu <liuhangbin@gmail•com>, Martin KaFai Lau <kafai@fb•com>
Cc: bpf@vger•kernel.org, netdev@vger•kernel.org,
"Jiri Benc" <jbenc@redhat•com>,
"Jesper Dangaard Brouer" <brouer@redhat•com>,
"Eelco Chaudron" <echaudro@redhat•com>,
ast@kernel•org, "Daniel Borkmann" <daniel@iogearbox•net>,
"Lorenzo Bianconi" <lorenzo.bianconi@redhat•com>,
"David Ahern" <dsahern@gmail•com>,
"Andrii Nakryiko" <andrii.nakryiko@gmail•com>,
"Alexei Starovoitov" <alexei.starovoitov@gmail•com>,
"John Fastabend" <john.fastabend@gmail•com>,
"Maciej Fijalkowski" <maciej.fijalkowski@intel•com>,
"Björn Töpel" <bjorn.topel@gmail•com>
Subject: Re: [PATCHv7 bpf-next 1/4] bpf: run devmap xdp_prog on flush instead of bulk enqueue
Date: Thu, 15 Apr 2021 11:22:19 +0200 [thread overview]
Message-ID: <87o8efkilw.fsf@toke.dk> (raw)
In-Reply-To: <20210415023746.GR2900@Leo-laptop-t470s>
Hangbin Liu <liuhangbin@gmail•com> writes:
> On Wed, Apr 14, 2021 at 05:17:11PM -0700, Martin KaFai Lau wrote:
>> > static void bq_xmit_all(struct xdp_dev_bulk_queue *bq, u32 flags)
>> > {
>> > struct net_device *dev = bq->dev;
>> > - int sent = 0, err = 0;
>> > + int sent = 0, drops = 0, err = 0;
>> > + unsigned int cnt = bq->count;
>> > + int to_send = cnt;
>> > int i;
>> >
>> > - if (unlikely(!bq->count))
>> > + if (unlikely(!cnt))
>> > return;
>> >
>> > - for (i = 0; i < bq->count; i++) {
>> > + for (i = 0; i < cnt; i++) {
>> > struct xdp_frame *xdpf = bq->q[i];
>> >
>> > prefetch(xdpf);
>> > }
>> >
>> > - sent = dev->netdev_ops->ndo_xdp_xmit(dev, bq->count, bq->q, flags);
>> > + if (bq->xdp_prog) {
>> bq->xdp_prog is used here
>>
>> > + to_send = dev_map_bpf_prog_run(bq->xdp_prog, bq->q, cnt, dev);
>> > + if (!to_send)
>> > + goto out;
>> > +
>> > + drops = cnt - to_send;
>> > + }
>> > +
>>
>> [ ... ]
>>
>> > static void bq_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
>> > - struct net_device *dev_rx)
>> > + struct net_device *dev_rx, struct bpf_prog *xdp_prog)
>> > {
>> > struct list_head *flush_list = this_cpu_ptr(&dev_flush_list);
>> > struct xdp_dev_bulk_queue *bq = this_cpu_ptr(dev->xdp_bulkq);
>> > @@ -412,18 +466,22 @@ static void bq_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
>> > /* Ingress dev_rx will be the same for all xdp_frame's in
>> > * bulk_queue, because bq stored per-CPU and must be flushed
>> > * from net_device drivers NAPI func end.
>> > + *
>> > + * Do the same with xdp_prog and flush_list since these fields
>> > + * are only ever modified together.
>> > */
>> > - if (!bq->dev_rx)
>> > + if (!bq->dev_rx) {
>> > bq->dev_rx = dev_rx;
>> > + bq->xdp_prog = xdp_prog;
>> bp->xdp_prog is assigned here and could be used later in bq_xmit_all().
>> How is bq->xdp_prog protected? Are they all under one rcu_read_lock()?
>> It is not very obvious after taking a quick look at xdp_do_flush[_map].
>>
>> e.g. what if the devmap elem gets deleted.
>
> Jesper knows better than me. From my veiw, based on the description of
> __dev_flush():
>
> On devmap tear down we ensure the flush list is empty before completing to
> ensure all flush operations have completed. When drivers update the bpf
> program they may need to ensure any flush ops are also complete.
Yeah, drivers call xdp_do_flush() before exiting their NAPI poll loop,
which also runs under one big rcu_read_lock(). So the storage in the
bulk queue is quite temporary, it's just used for bulking to increase
performance :)
-Toke
next prev parent reply other threads:[~2021-04-15 9:22 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-14 12:26 [PATCHv7 bpf-next 0/4] xdp: extend xdp_redirect_map with broadcast support Hangbin Liu
2021-04-14 12:26 ` [PATCHv7 bpf-next 1/4] bpf: run devmap xdp_prog on flush instead of bulk enqueue Hangbin Liu
2021-04-15 0:17 ` Martin KaFai Lau
2021-04-15 2:37 ` Hangbin Liu
2021-04-15 9:22 ` Toke Høiland-Jørgensen [this message]
2021-04-15 17:35 ` Martin KaFai Lau
2021-04-15 18:21 ` Jesper Dangaard Brouer
2021-04-15 20:29 ` Toke Høiland-Jørgensen
2021-04-16 0:39 ` Martin KaFai Lau
2021-04-16 10:03 ` Toke Høiland-Jørgensen
2021-04-16 18:20 ` Martin KaFai Lau
2021-04-16 13:45 ` Jesper Dangaard Brouer
2021-04-16 14:35 ` Toke Høiland-Jørgensen
2021-04-16 18:22 ` Martin KaFai Lau
2021-04-17 0:23 ` Paul E. McKenney
2021-04-17 12:27 ` Toke Høiland-Jørgensen
2021-04-19 16:58 ` Paul E. McKenney
2021-04-19 18:12 ` Toke Høiland-Jørgensen
2021-04-19 18:32 ` Paul E. McKenney
2021-04-19 21:21 ` Toke Høiland-Jørgensen
2021-04-19 21:41 ` Paul E. McKenney
2021-04-19 22:16 ` Toke Høiland-Jørgensen
2021-04-19 22:31 ` Paul E. McKenney
2021-04-21 14:24 ` Toke Høiland-Jørgensen
2021-04-21 14:59 ` Paul E. McKenney
2021-04-21 19:59 ` Toke Høiland-Jørgensen
2021-04-21 20:51 ` Paul E. McKenney
2021-04-21 21:10 ` Toke Høiland-Jørgensen
2021-04-21 21:30 ` Paul E. McKenney
2021-04-21 22:00 ` Toke Høiland-Jørgensen
2021-04-21 22:31 ` Paul E. McKenney
2021-04-22 14:30 ` Toke Høiland-Jørgensen
2021-04-14 12:26 ` [PATCHv7 bpf-next 2/4] xdp: extend xdp_redirect_map with broadcast support Hangbin Liu
2021-04-15 0:23 ` Martin KaFai Lau
2021-04-15 2:21 ` Hangbin Liu
2021-04-15 9:29 ` Toke Høiland-Jørgensen
2021-04-14 12:26 ` [PATCHv7 bpf-next 3/4] sample/bpf: add xdp_redirect_map_multi for redirect_map broadcast test Hangbin Liu
2021-04-14 12:26 ` [PATCHv7 bpf-next 4/4] selftests/bpf: add xdp_redirect_multi test Hangbin Liu
2021-04-14 14:16 ` [PATCHv7 bpf-next 0/4] xdp: extend xdp_redirect_map with broadcast support Toke Høiland-Jørgensen
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