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Date: Wed, 25 Jan 2023 16:10:32 +0100
From: Jesper Dangaard Brouer <jbrouer@...hat.com>
To: sdf@...gle.com, Jesper Dangaard Brouer <jbrouer@...hat.com>
Cc: brouer@...hat.com, bpf@...r.kernel.org, ast@...nel.org,
daniel@...earbox.net, andrii@...nel.org, martin.lau@...ux.dev,
song@...nel.org, yhs@...com, john.fastabend@...il.com,
kpsingh@...nel.org, haoluo@...gle.com, jolsa@...nel.org,
David Ahern <dsahern@...il.com>,
Jakub Kicinski <kuba@...nel.org>,
Willem de Bruijn <willemb@...gle.com>,
Anatoly Burakov <anatoly.burakov@...el.com>,
Alexander Lobakin <alexandr.lobakin@...el.com>,
Magnus Karlsson <magnus.karlsson@...il.com>,
Maryam Tahhan <mtahhan@...hat.com>, xdp-hints@...-project.net,
netdev@...r.kernel.org,
Toke Høiland-Jørgensen <toke@...hat.com>
Subject: Re: [PATCH bpf-next v8 17/17] selftests/bpf: Simple program to dump
XDP RX metadata
On 24/01/2023 19.48, sdf@...gle.com wrote:
> On 01/24, Stanislav Fomichev wrote:
>> On Tue, Jan 24, 2023 at 7:26 AM Jesper Dangaard Brouer
>> <jbrouer@...hat.com> wrote:
>> >
>> >
>> > Testing this on mlx5 and I'm not getting the RX-timestamp.
>> > See command details below.
>
>> CC'ed Toke since I've never tested mlx5 myself.
>> I was pretty close to getting the setup late last week, let me try to
>> see whether it's ready or not.
>
>> > On 19/01/2023 23.15, Stanislav Fomichev wrote:
>> > > To be used for verification of driver implementations. Note that
>> > > the skb path is gone from the series, but I'm still keeping the
>> > > implementation for any possible future work.
>> > >
>> > > $ xdp_hw_metadata <ifname>
>> >
>> > sudo ./xdp_hw_metadata mlx5p1
>> >
>> > Output:
>> > [...cut ...]
>> > open bpf program...
>> > load bpf program...
>> > prepare skb endpoint...
>> > XXX timestamping_enable(): setsockopt(SO_TIMESTAMPING) ret:0
>> > prepare xsk map...
>> > map[0] = 3
>> > map[1] = 4
>> > map[2] = 5
>> > map[3] = 6
>> > map[4] = 7
>> > map[5] = 8
>> > attach bpf program...
>> > poll: 0 (0)
>> > poll: 0 (0)
>> > poll: 0 (0)
>> > poll: 1 (0)
>> > xsk_ring_cons__peek: 1
>> > 0x1821788: rx_desc[0]->addr=100000000008000 addr=8100 comp_addr=8000
>> > rx_timestamp: 0
>> > rx_hash: 2773355807
>> > 0x1821788: complete idx=8 addr=8000
>> > poll: 0 (0)
>> >
>> > The trace_pipe:
>> >
>> > $ sudo cat /sys/kernel/debug/tracing/trace_pipe
>> > <idle>-0 [005] ..s2. 2722.884762: bpf_trace_printk:
>> > forwarding UDP:9091 to AF_XDP
>> > <idle>-0 [005] ..s2. 2722.884771: bpf_trace_printk:
>> > populated rx_hash with 2773355807
>> >
>> >
>> > > On the other machine:
>> > >
>> > > $ echo -n xdp | nc -u -q1 <target> 9091 # for AF_XDP
>> >
>> > Fixing the source-port to see if RX-hash remains the same.
>> >
>> > $ echo xdp | nc --source-port=2000 --udp 198.18.1.1 9091
>> >
>> > > $ echo -n skb | nc -u -q1 <target> 9092 # for skb
>> > >
>> > > Sample output:
>> > >
>> > > # xdp
>> > > xsk_ring_cons__peek: 1
>> > > 0x19f9090: rx_desc[0]->addr=100000000008000 addr=8100
>> comp_addr=8000
>> > > rx_timestamp_supported: 1
>> > > rx_timestamp: 1667850075063948829
>> > > 0x19f9090: complete idx=8 addr=8000
>> >
>> > xsk_ring_cons__peek: 1
>> > 0x1821788: rx_desc[0]->addr=100000000008000 addr=8100 comp_addr=8000
>> > rx_timestamp: 0
>> > rx_hash: 2773355807
>> > 0x1821788: complete idx=8 addr=8000
>> >
>> > It doesn't look like hardware RX-timestamps are getting enabled.
>> >
>> > [... cut to relevant code ...]
>> >
>> > > diff --git a/tools/testing/selftests/bpf/xdp_hw_metadata.c
>> b/tools/testing/selftests/bpf/xdp_hw_metadata.c
>> > > new file mode 100644
>> > > index 000000000000..0008f0f239e8
>> > > --- /dev/null
>> > > +++ b/tools/testing/selftests/bpf/xdp_hw_metadata.c
>> > > @@ -0,0 +1,403 @@
>> > [...]
>> >
>> > > +static void timestamping_enable(int fd, int val)
>> > > +{
>> > > + int ret;
>> > > +
>> > > + ret = setsockopt(fd, SOL_SOCKET, SO_TIMESTAMPING, &val,
>> sizeof(val));
>> > > + if (ret < 0)
>> > > + error(-1, errno, "setsockopt(SO_TIMESTAMPING)");
>> > > +}
>> > > +
>> > > +int main(int argc, char *argv[])
>> > > +{
>> > [...]
>> >
>> > > + printf("prepare skb endpoint...\n");
>> > > + server_fd = start_server(AF_INET6, SOCK_DGRAM, NULL, 9092,
>> 1000);
>> > > + if (server_fd < 0)
>> > > + error(-1, errno, "start_server");
>> > > + timestamping_enable(server_fd,
>> > > + SOF_TIMESTAMPING_SOFTWARE |
>> > > + SOF_TIMESTAMPING_RAW_HARDWARE);
>> > > +
>> >
>> > I don't think this timestamping_enable() with these flags are enough to
>> > enable hardware timestamping.
>
> Yeah, agreed, looks like that's the issue. timestamping_enable() has
> been used for the xdp->skb path that I've eventually removed from the
> series, so it's mostly a noop here..
>
> Maybe you can try the following before I send a proper patch?
Yes, below patch fixed the issue, thx.
Now I get HW timestamps, plus I added some software CLOCK_TAI timestamps
to compare against.
Output is now:
poll: 1 (0)
xsk_ring_cons__peek: 1
0xf64788: rx_desc[0]->addr=100000000008000 addr=8100 comp_addr=8000
rx_hash: 3697961069
rx_timestamp: 1674657672142214773 (sec:1674657672.1422)
XDP RX-time: 1674657709561774876 (sec:1674657709.5618) delta sec:37.4196
AF_XDP time: 1674657709561871034 (sec:1674657709.5619) delta
sec:0.0001 (96.158 usec)
0xf64788: complete idx=8 addr=8000
My NIC hardware clock is clearly not synced with system time, as above
delta say 37.4 seconds between HW and XDP timestamps (using
bpf_ktime_get_tai_ns()).
Time between XDP and AF_XDP wakeup is reported to be 96 usec, which is
also higher than I expected. As explained in [1] this is caused by CPU
sleep states.
My /dev/cpu_dma_latency was set to 2000000000. Applying tuned-adm
profile latency-performance this value change to 2.
$ sudo hexdump --format '"%d\n"' /dev/cpu_dma_latency
2000000000
$ sudo hexdump --format '"%d\n"' /dev/cpu_dma_latency
2
Now the time between XDP and AF_XDP wakeup is reduced to approx 12 usec.
rx_timestamp: 1674659206344977544 (sec:1674659206.3450)
XDP RX-time: 1674659243776087765 (sec:1674659243.7761) delta sec:37.4311
AF_XDP time: 1674659243776099841 (sec:1674659243.7761) delta
sec:0.0000 (12.076 usec)
[1]
https://github.com/xdp-project/bpf-examples/tree/master/AF_XDP-interaction
> diff --git a/tools/testing/selftests/bpf/xdp_hw_metadata.c
> b/tools/testing/selftests/bpf/xdp_hw_metadata.c
> index 0008f0f239e8..dceddb17fbc9 100644
> --- a/tools/testing/selftests/bpf/xdp_hw_metadata.c
> +++ b/tools/testing/selftests/bpf/xdp_hw_metadata.c
> @@ -24,6 +24,7 @@
> #include <linux/net_tstamp.h>
> #include <linux/udp.h>
> #include <linux/sockios.h>
> +#include <linux/net_tstamp.h>
> #include <sys/mman.h>
> #include <net/if.h>
> #include <poll.h>
> @@ -278,13 +279,37 @@ static int rxq_num(const char *ifname)
>
> ret = ioctl(fd, SIOCETHTOOL, &ifr);
> if (ret < 0)
> - error(-1, errno, "socket");
> + error(-1, errno, "ioctl(SIOCETHTOOL)");
>
> close(fd);
>
> return ch.rx_count + ch.combined_count;
> }
>
> +static void hwtstamp_enable(const char *ifname)
> +{
> + struct hwtstamp_config cfg = {
> + .rx_filter = HWTSTAMP_FILTER_ALL,
> +
> + };
> +
> + struct ifreq ifr = {
> + .ifr_data = (void *)&cfg,
> + };
> + strcpy(ifr.ifr_name, ifname);
> + int fd, ret;
> +
> + fd = socket(AF_UNIX, SOCK_DGRAM, 0);
> + if (fd < 0)
> + error(-1, errno, "socket");
> +
> + ret = ioctl(fd, SIOCSHWTSTAMP, &ifr);
> + if (ret < 0)
> + error(-1, errno, "ioctl(SIOCSHWTSTAMP)");
> +
> + close(fd);
> +}
> +
> static void cleanup(void)
> {
> LIBBPF_OPTS(bpf_xdp_attach_opts, opts);
> @@ -341,6 +366,8 @@ int main(int argc, char *argv[])
>
> printf("rxq: %d\n", rxq);
>
> + hwtstamp_enable(ifname);
> +
> rx_xsk = malloc(sizeof(struct xsk) * rxq);
> if (!rx_xsk)
> error(-1, ENOMEM, "malloc");
>
>
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