Variable 'protocol' is being assigned but is never used hence it is
redundant and can be removed.

Cleans up clang warning:
warning: variable 'protocol' set but not used [-Wunused-but-set-variable]
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Variable last_rule_idx is being assigned but is never used hence it is
redundant and can be removed.

Cleans up clang warning:
warning: variable 'last_rule_idx' set but not used [-Wunused-but-set-variable]
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Acked-by: NClaudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Variable 'inc' is being assigned but is never used hence it is
redundant and can be removed.

Cleans up clang warning:
warning: variable 'inc' set but not used [-Wunused-but-set-variable]
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Acked-by: NFugang Duan <fugang.duan@nxp.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Pointer req and variable func are being assigned but are never used
hence they are redundant and can be removed.

Cleans up clang warnings:
warning: variable 'req' set but not used [-Wunused-but-set-variable]
warning: variable 'func' set but not used [-Wunused-but-set-variable]
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Variable 'freed' is being assigned but is never used hence it is
redundant and can be removed.

Cleans up clang warning:
warning: variable 'freed' set but not used [-Wunused-but-set-variable]
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Pointer rxd is being assigned but is never used hence it is
redundant and can be removed.

Cleans up clang warning:
warning: variable 'rxb' set but not used [-Wunused-but-set-variable]
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Variable old_duplex is being assigned but is never used hence it is
redundant and can be removed.

Cleans up clang warning:
warning: variable 'old_duplex' set but not used [-Wunused-but-set-variable]
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Pointer rxdesc is being assigned but is never used hence it is
redundant and can be removed.

Cleans up clang warning:
warning: variable 'rxdesc' set but not used [-Wunused-but-set-variable]
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Variable 'off' is being assigned but is never used hence it is
redundant and can be removed.

Cleans up clang warning:
warning: variable 'off' set but not used [-Wunused-but-set-variable]
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Jesus Sanchez-Palencia says:

====================
Scheduled packet Transmission: ETF

Changes since v1:
  - moved struct sock_txtime from socket.h to uapi net_tstamp.h;
  - sk_clockid was changed from u16 to u8;
  - sk_txtime_flags was changed from u16 to a u8 bit field in struct sock;
  - the socket option flags are now validated in sock_setsockopt();
  - added SO_EE_ORIGIN_TXTIME;
  - sockc.transmit_time is now initialized from all IPv4 Tx paths;
  - added support for the IPv6 Tx path;

Overview
========

This work consists of a set of kernel interfaces that can be used by
applications that require (time-based) Scheduled Tx of packets.
It is comprised by 3 new components to the kernel:

  - SO_TXTIME: socket option + cmsg programming interfaces.

  - etf: the "earliest txtime first" qdisc, that provides per-queue
	 TxTime-based scheduling. This has been renamed from 'tbs' to
	 'etf' to better describe its functionality.

  - taprio: the "time-aware priority scheduler" qdisc, that provides
	    per-port Time-Aware scheduling;

This patchset is providing the first 2 components, which have been
developed for longer. The taprio qdisc will be shared as an RFC separately
(shortly).

Note that this series is a follow up of the "Time based packet
transmission" RFCv3 [1].

etf (formerly known as 'tbs')
=============================

For applications/systems that the concept of time slices isn't precise
enough, the etf qdisc allows applications to control the instant when
a packet should leave the network controller. When used in conjunction
with taprio, it can also be used in case the application needs to
control with greater guarantee the offset into each time slice a packet
will be sent. Another use case of etf, is when only a small number of
applications on a system are time sensitive, so it can then be used
with a more traditional root qdisc (like mqprio).

The etf qdisc is designed so it buffers packets until a configurable
time before their deadline (Tx time). The qdisc uses a rbtree internally
so the buffered packets are always 'ordered' by their txtime (deadline)
and will be dequeued following the earliest txtime first.

It relies on the SO_TXTIME API set for receiving the per-packet timestamp
(txtime) as well as the config flags for each socket: the clockid to be
used as a reference, if the expected mode of txtime for that socket is
deadline or strict mode, and if packet drops should be reported on the
socket's error queue or not.

The qdisc will drop any packets with a Tx time in the past, or if a
packet expires while waiting for being dequeued. Drops can be reported
as errors back to userspace through the socket's error queue.

Example configuration:

$ tc qdisc add dev enp2s0 parent 100:1 etf offload delta 200000 \
            clockid CLOCK_TAI

Here, the Qdisc will use HW offload for the txtime control.
Packets will be dequeued by the qdisc "delta" (200000) nanoseconds before
their transmission time. Because this will be using HW offload and
since dynamic clocks are not supported by hrtimers, the system clock
and the PHC clock must be synchronized for this mode to behave as expected.

A more complete example can be found here, with instructions of how to
test it:

https://gist.github.com/jeez/bd3afeff081ba64a695008dd8215866f [2]

Note that we haven't modified the qdisc so it uses a timerqueue because
the modification needed was increasing the number of cachelines of a sk_buff.

This series is also hosted on github and can be found at [3].
The companion iproute2 patches can be found at [4].

[1] https://patchwork.ozlabs.org/cover/882342/

[2] github doesn't make it clear, but the gist can be cloned like this:
$ git clone https://gist.github.com/jeez/bd3afeff081ba64a695008dd8215866f scheduled-tx-tests

[3] https://github.com/jeez/linux/tree/etf-v2

[4] https://github.com/jeez/iproute2/tree/etf-v2
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Use the socket error queue for reporting dropped packets if the
socket has enabled that feature through the SO_TXTIME API.

Packets are dropped either on enqueue() if they aren't accepted by the
qdisc or on dequeue() if the system misses their deadline. Those are
reported as different errors so applications can react accordingly.

Userspace can retrieve the errors through the socket error queue and the
corresponding cmsg interfaces. A struct sock_extended_err* is used for
returning the error data, and the packet's timestamp can be retrieved by
adding both ee_data and ee_info fields as e.g.:

    ((__u64) serr->ee_data << 32) + serr->ee_info

This feature is disabled by default and must be explicitly enabled by
applications. Enabling it can bring some overhead for the Tx cycles
of the application.
Signed-off-by: NJesus Sanchez-Palencia <jesus.sanchez-palencia@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Implement HW offload support for SO_TXTIME through igb's Launchtime
feature. This is done by extending igb_setup_tc() so it supports
TC_SETUP_QDISC_ETF and configuring i210 so time based transmit
arbitration is enabled.

The FQTSS transmission mode added before is extended so strict
priority (SP) queues wait for stream reservation (SR) ones.
igb_config_tx_modes() is extended so it can support enabling/disabling
Launchtime following the previous approach used for the credit-based
shaper (CBS).

As the previous flow, FQTSS transmission mode is enabled automatically
by the driver once Launchtime (or CBS, as before) is enabled.
Similarly, it's automatically disabled when the feature is disabled
for the last queue that had it setup on.

The driver just consumes the transmit times from the skbuffs directly,
so no special handling is done in case an 'invalid' time is provided.
We assume this has been handled by the ETF qdisc already.
Signed-off-by: NJesus Sanchez-Palencia <jesus.sanchez-palencia@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Currently, skb_tx_timestamp() is being called before the Tx
descriptors are prepared in igb_xmit_frame_ring(), which happens
during either the igb_tso() or igb_tx_csum() calls.

Given that now the skb->tstamp might be used to carry the timestamp
for SO_TXTIME, we must only call skb_tx_timestamp() after the
information has been copied into the Tx descriptors.
Signed-off-by: NJesus Sanchez-Palencia <jesus.sanchez-palencia@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Split code into a separate function (igb_offload_apply()) that will be
used by ETF offload implementation.
Signed-off-by: NJesus Sanchez-Palencia <jesus.sanchez-palencia@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Currently the data transmission arbitration algorithm - DataTranARB
field on TQAVCTRL reg - is always set to CBS when the Tx mode is
changed from legacy to 'Qav' mode.

Make that configuration a bit more granular in preparation for the
upcoming Launchtime enabling patches, since CBS and Launchtime can be
enabled separately. That is achieved by moving the DataTranARB setup
to igb_config_tx_modes() instead.

Similarly, when disabling CBS we must check if it has been disabled
for all queues, and clear the DataTranARB accordingly.
Signed-off-by: NJesus Sanchez-Palencia <jesus.sanchez-palencia@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Make this function retrieve what it needs from the Tx ring being
addressed since it already relies on what had been saved on it before.
Also, since this function will be used by the upcoming Launchtime
patches rename it to better reflect its intention. Note that
Launchtime is not part of what 802.1Qav specifies, but the i210
datasheet refers to this set of functionality as "Qav Transmission
Mode".

Here we also perform a tiny refactor at is_any_cbs_enabled(), and add
further documentation to igb_setup_tx_mode().
Signed-off-by: NJesus Sanchez-Palencia <jesus.sanchez-palencia@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add infra so etf qdisc supports HW offload of time-based transmission.

For hw offload, the time sorted list is still used, so packets are
dequeued always in order of txtime.

Example:

$ tc qdisc replace dev enp2s0 parent root handle 100 mqprio num_tc 3 \
           map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 queues 1@0 1@1 2@2 hw 0

$ tc qdisc add dev enp2s0 parent 100:1 etf offload delta 100000 \
	   clockid CLOCK_REALTIME

In this example, the Qdisc will use HW offload for the control of the
transmission time through the network adapter. The hrtimer used for
packets scheduling inside the qdisc will use the clockid CLOCK_REALTIME
as reference and packets leave the Qdisc "delta" (100000) nanoseconds
before their transmission time. Because this will be using HW offload and
since dynamic clocks are not supported by the hrtimer, the system clock
and the PHC clock must be synchronized for this mode to behave as
expected.
Signed-off-by: NJesus Sanchez-Palencia <jesus.sanchez-palencia@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The ETF (Earliest TxTime First) qdisc uses the information added
earlier in this series (the socket option SO_TXTIME and the new
role of sk_buff->tstamp) to schedule packets transmission based
on absolute time.

For some workloads, just bandwidth enforcement is not enough, and
precise control of the transmission of packets is necessary.

Example:

$ tc qdisc replace dev enp2s0 parent root handle 100 mqprio num_tc 3 \
           map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 queues 1@0 1@1 2@2 hw 0

$ tc qdisc add dev enp2s0 parent 100:1 etf delta 100000 \
           clockid CLOCK_TAI

In this example, the Qdisc will provide SW best-effort for the control
of the transmission time to the network adapter, the time stamp in the
socket will be in reference to the clockid CLOCK_TAI and packets
will leave the qdisc "delta" (100000) nanoseconds before its transmission
time.

The ETF qdisc will buffer packets sorted by their txtime. It will drop
packets on enqueue() if their skbuff clockid does not match the clock
reference of the Qdisc. Moreover, on dequeue(), a packet will be dropped
if it expires while being enqueued.

The qdisc also supports the SO_TXTIME deadline mode. For this mode, it
will dequeue a packet as soon as possible and change the skb timestamp
to 'now' during etf_dequeue().

Note that both the qdisc's and the SO_TXTIME ABIs allow for a clockid
to be configured, but it's been decided that usage of CLOCK_TAI should
be enforced until we decide to allow for other clockids to be used.
The rationale here is that PTP times are usually in the TAI scale, thus
no other clocks should be necessary. For now, the qdisc will return
EINVAL if any clocks other than CLOCK_TAI are used.
Signed-off-by: NJesus Sanchez-Palencia <jesus.sanchez-palencia@intel.com>
Signed-off-by: NVinicius Costa Gomes <vinicius.gomes@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This adds 'qdisc_watchdog_init_clockid()' that allows a clockid to be
passed, this allows other time references to be used when scheduling
the Qdisc to run.
Signed-off-by: NVinicius Costa Gomes <vinicius.gomes@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

For raw layer-2 packets, copy the desired future transmit time from
the CMSG cookie into the skb.
Signed-off-by: NRichard Cochran <rcochran@linutronix.de>
Signed-off-by: NJesus Sanchez-Palencia <jesus.sanchez-palencia@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add a struct sockcm_cookie parameter to ip6_setup_cork() so
we can easily re-use the transmit_time field from struct inet_cork
for most paths, by copying the timestamp from the CMSG cookie.
This is later copied into the skb during __ip6_make_skb().

For the raw fast path, also pass the sockcm_cookie as a parameter
so we can just perform the copy at rawv6_send_hdrinc() directly.
Signed-off-by: NJesus Sanchez-Palencia <jesus.sanchez-palencia@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add a transmit_time field to struct inet_cork, then copy the
timestamp from the CMSG cookie at ip_setup_cork() so we can
safely copy it into the skb later during __ip_make_skb().

For the raw fast path, just perform the copy at raw_send_hdrinc().
Signed-off-by: NRichard Cochran <rcochran@linutronix.de>
Signed-off-by: NJesus Sanchez-Palencia <jesus.sanchez-palencia@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch introduces SO_TXTIME. User space enables this option in
order to pass a desired future transmit time in a CMSG when calling
sendmsg(2). The argument to this socket option is a 8-bytes long struct
provided by the uapi header net_tstamp.h defined as:

struct sock_txtime {
	clockid_t 	clockid;
	u32		flags;
};

Note that new fields were added to struct sock by filling a 2-bytes
hole found in the struct. For that reason, neither the struct size or
number of cachelines were altered.
Signed-off-by: NRichard Cochran <rcochran@linutronix.de>
Signed-off-by: NJesus Sanchez-Palencia <jesus.sanchez-palencia@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This is done in preparation for the upcoming time based transmission
patchset. Now that skb->tstamp will be used to hold packet's txtime,
we must ensure that it is being cleared when traversing namespaces.
Also, doing that from skb_scrub_packet() before the early return would
break our feature when tunnels are used.
Signed-off-by: NJesus Sanchez-Palencia <jesus.sanchez-palencia@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Warning level 2 was used: -Wimplicit-fallthrough=2
Signed-off-by: NGustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

For Embedded use where e.g. AX88772B chips may be used without external
EEPROMs the boot loader may choose to pass the MAC address to be used
via device tree. Therefore, allow for optionally getting the MAC
address from device tree data e.g. as follows (excerpt from a T30 based
board, local-mac-address to be filled in by boot loader):

/* EHCI instance 1: USB2_DP/N -> AX88772B */
usb@7d004000 {
	status = "okay";
	#address-cells = <1>;
	#size-cells = <0>;
	asix@1 {
		reg = <1>;
		local-mac-address = [00 00 00 00 00 00];
	};
};
Signed-off-by: NMarcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

'keys_ex' is malloced by tcf_pedit_keys_ex_parse() in tcf_pedit_init()
but not all of the error handle path free it, this may cause memory
leak. This patch fix it.

Fixes: 71d0ed70 ("net/act_pedit: Support using offset relative to the conventional network headers")
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Acked-by: NCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Nikolay Aleksandrov says:

====================
bridge: iproute2 isolated port and selftests

Add support to iproute2 for port isolation config and selftests for it.
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This test checks if the bridge port isolation feature works as expected
by performing ping/ping6 tests between hosts that are isolated (should
not work) and between an isolated and non-isolated hosts (should work).
Same test is performed for flooding from and to isolated and
non-isolated ports.
Signed-off-by: NNikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Extract ping and ping6 command execution so the return value can be
checked by the caller, this is needed for port isolation tests that are
intended to fail.
Signed-off-by: NNikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Toshiaki Makita says:

====================
vhost_net: Avoid vq kicks during busyloop

Under heavy load vhost tx busypoll tend not to suppress vq kicks, which
causes poor guest tx performance. The detailed scenario is described in
commitlog of patch 2.
Rx seems not to have that serious problem, but for consistency I made a
similar change on rx to avoid rx wakeups (patch 3).
Additionary patch 4 is to avoid rx kicks under heavy load during
busypoll.

Tx performance is greatly improved by this change. I don't see notable
performance change on rx with this series though.

Performance numbers (tx):

- Bulk transfer from guest to external physical server.
    [Guest]->vhost_net->tap--(XDP_REDIRECT)-->i40e --(wire)--> [Server]
- Set 10us busypoll.
- Guest disables checksum and TSO because of host XDP.
- Measured single flow Mbps by netperf, and kicks by perf kvm stat
  (EPT_MISCONFIG event).

                            Before              After
                          Mbps  kicks/s      Mbps  kicks/s
UDP_STREAM 1472byte              247758                 27
                Send   3645.37            6958.10
                Recv   3588.56            6958.10
              1byte                9865                 37
                Send      4.34               5.43
                Recv      4.17               5.26
TCP_STREAM             8801.03    45794   9592.77     2884

v2:
- Split patches into 3 parts (renaming variables, tx-kick fix, rx-wakeup
  fix).
- Avoid rx-kicks too (patch 4).
- Don't memorize endtime as it is not needed for now.
====================
Acked-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

We may run out of avail rx ring descriptor under heavy load but busypoll
did not detect it so busypoll may have exited prematurely. Avoid this by
checking rx ring full during busypoll.
Signed-off-by: NToshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Acked-by: NJason Wang <jasowang@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

We may run handle_rx() while rx work is queued. For example a packet can
push the rx work during the window before handle_rx calls
vhost_net_disable_vq().
In that case busypoll immediately exits due to vhost_has_work()
condition and enables vq again. This can lead to another unnecessary rx
wake-ups, so poll rx work instead of enabling the vq.
Signed-off-by: NToshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Acked-by: NJason Wang <jasowang@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Under heavy load vhost busypoll may run without suppressing
notification. For example tx zerocopy callback can push tx work while
handle_tx() is running, then busyloop exits due to vhost_has_work()
condition and enables notification but immediately reenters handle_tx()
because the pushed work was tx. In this case handle_tx() tries to
disable notification again, but when using event_idx it by design
cannot. Then busyloop will run without suppressing notification.
Another example is the case where handle_tx() tries to enable
notification but avail idx is advanced so disables it again. This case
also leads to the same situation with event_idx.

The problem is that once we enter this situation busyloop does not work
under heavy load for considerable amount of time, because notification
is likely to happen during busyloop and handle_tx() immediately enables
notification after notification happens. Specifically busyloop detects
notification by vhost_has_work() and then handle_tx() calls
vhost_enable_notify(). Because the detected work was the tx work, it
enters handle_tx(), and enters busyloop without suppression again.
This is likely to be repeated, so with event_idx we are almost not able
to suppress notification in this case.

To fix this, poll the work instead of enabling notification when
busypoll is interrupted by something. IMHO vhost_has_work() is kind of
interruption rather than a signal to completely cancel the busypoll, so
let's run busypoll after the necessary work is done.
Signed-off-by: NToshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Acked-by: NJason Wang <jasowang@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

So we can easily see which variable is for which, tx or rx.
Signed-off-by: NToshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Acked-by: NJason Wang <jasowang@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The new action inheritdsfield copies the field DS of
IPv4 and IPv6 packets into skb->priority. This enables
later classification of packets based on the DS field.

v5:
*Update the drop counter for TC_ACT_SHOT

v4:
*Not allow setting flags other than the expected ones.

*Allow dumping the pure flags.

v3:
*Use optional flags, so that it won't break old versions of tc.

*Allow users to set both SKBEDIT_F_PRIORITY and SKBEDIT_F_INHERITDSFIELD flags.

v2:
*Fix the style issue

*Move the code from skbmod to skbedit

Original idea by Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: NQiaobin Fu <qiaobinf@bu.edu>
Reviewed-by: NMichel Machado <michel@digirati.com.br>
Acked-by: NJamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: NMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: NDavide Caratti <dcaratti@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Petr Machata says:

====================
More mirror-to-gretap tests with bridge in UL

This patchset adds two more tests where the mirror-to-gretap has a
bridge in underlay packet path, without a VLAN above or below that
bridge.

In patch #1, a non-VLAN-filtering bridge is tested.

In patch #2, a VLAN-filtering bridge is tested.
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Test for "tc action mirred egress mirror" that mirrors to gretap when
the underlay route points at a VLAN-aware bridge (802.1q).
Signed-off-by: NPetr Machata <petrm@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Test for "tc action mirred egress mirror" that mirrors to gretap when
the underlay route points at a VLAN-unaware bridge (802.1d).
Signed-off-by: NPetr Machata <petrm@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Edward Cree says:

====================
Handle multiple received packets at each stage

This patch series adds the capability for the network stack to receive a
 list of packets and process them as a unit, rather than handling each
 packet singly in sequence.  This is done by factoring out the existing
 datapath code at each layer and wrapping it in list handling code.

The motivation for this change is twofold:
* Instruction cache locality.  Currently, running the entire network
  stack receive path on a packet involves more code than will fit in the
  lowest-level icache, meaning that when the next packet is handled, the
  code has to be reloaded from more distant caches.  By handling packets
  in "row-major order", we ensure that the code at each layer is hot for
  most of the list.  (There is a corresponding downside in _data_ cache
  locality, since we are now touching every packet at every layer, but in
  practice there is easily enough room in dcache to hold one cacheline of
  each of the 64 packets in a NAPI poll.)
* Reduction of indirect calls.  Owing to Spectre mitigations, indirect
  function calls are now more expensive than ever; they are also heavily
  used in the network stack's architecture (see [1]).  By replacing 64
  indirect calls to the next-layer per-packet function with a single
  indirect call to the next-layer list function, we can save CPU cycles.

Drivers pass an SKB list to the stack at the end of the NAPI poll; this
 gives a natural batch size (the NAPI poll weight) and avoids waiting at
 the software level for further packets to make a larger batch (which
 would add latency).  It also means that the batch size is automatically
 tuned by the existing interrupt moderation mechanism.
The stack then runs each layer of processing over all the packets in the
 list before proceeding to the next layer.  Where the 'next layer' (or
 the context in which it must run) differs among the packets, the stack
 splits the list; this 'late demux' means that packets which differ only
 in later headers (e.g. same L2/L3 but different L4) can traverse the
 early part of the stack together.
Also, where the next layer is not (yet) list-aware, the stack can revert
 to calling the rest of the stack in a loop; this allows gradual/creeping
 listification, with no 'flag day' patch needed to listify everything.

Patches 1-2 simply place received packets on a list during the event
 processing loop on the sfc EF10 architecture, then call the normal stack
 for each packet singly at the end of the NAPI poll.  (Analogues of patch
 #2 for other NIC drivers should be fairly straightforward.)
Patches 3-9 extend the list processing as far as the IP receive handler.

Patches 1-2 alone give about a 10% improvement in packet rate in the
 baseline test; adding patches 3-9 raises this to around 25%.

Performance measurements were made with NetPerf UDP_STREAM, using 1-byte
 packets and a single core to handle interrupts on the RX side; this was
 in order to measure as simply as possible the packet rate handled by a
 single core.  Figures are in Mbit/s; divide by 8 to obtain Mpps.  The
 setup was tuned for maximum reproducibility, rather than raw performance.
 Full details and more results (both with and without retpolines) from a
 previous version of the patch series are presented in [2].

The baseline test uses four streams, and multiple RXQs all bound to a
 single CPU (the netperf binary is bound to a neighbouring CPU).  These
 tests were run with retpolines.
net-next: 6.91 Mb/s (datum)
 after 9: 8.46 Mb/s (+22.5%)
Note however that these results are not robust; changes in the parameters
 of the test sometimes shrink the gain to single-digit percentages.  For
 instance, when using only a single RXQ, only a 4% gain was seen.

One test variation was the use of software filtering/firewall rules.
 Adding a single iptables rule (UDP port drop on a port range not matching
 the test traffic), thus making the netfilter hook have work to do,
 reduced baseline performance but showed a similar gain from the patches:
net-next: 5.02 Mb/s (datum)
 after 9: 6.78 Mb/s (+35.1%)

Similarly, testing with a set of TC flower filters (kindly supplied by
 Cong Wang) gave the following:
net-next: 6.83 Mb/s (datum)
 after 9: 8.86 Mb/s (+29.7%)

These data suggest that the batching approach remains effective in the
 presence of software switching rules, and perhaps even improves the
 performance of those rules by allowing them and their codepaths to stay
 in cache between packets.

Changes from v3:
* Fixed build error when CONFIG_NETFILTER=n (thanks kbuild).

Changes from v2:
* Used standard list handling (and skb->list) instead of the skb-queue
  functions (that use skb->next, skb->prev).
  - As part of this, changed from a "dequeue, process, enqueue" model to
    using list_for_each_safe, list_del, and (new) list_cut_before.
* Altered __netif_receive_skb_core() changes in patch 6 as per Willem de
  Bruijn's suggestions (separate **ppt_prev from *pt_prev; renaming).
* Removed patches to Generic XDP, since they were producing no benefit.
  I may revisit them later.
* Removed RFC tags.

Changes from v1:
* Rebased across 2 years' net-next movement (surprisingly straightforward).
  - Added Generic XDP handling to netif_receive_skb_list_internal()
  - Dealt with changes to PFMEMALLOC setting APIs
* General cleanup of code and comments.
* Skipped function calls for empty lists at various points in the stack
  (patch #9).
* Added listified Generic XDP handling (patches 10-12), though it doesn't
  seem to help (see above).
* Extended testing to cover software firewalls / netfilter etc.

[1] http://vger.kernel.org/netconf2018_files/DavidMiller_netconf2018.pdf
[2] http://vger.kernel.org/netconf2018_files/EdwardCree_netconf2018.pdf
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>