[ovs-dev] [RFC v7 00/13] Support multi-segment mbufs
Eelco Chaudron
echaudro at redhat.com
Thu Jun 7 12:48:46 UTC 2018
I'm planning on reviewing this patchset, but when I applied the patch to
master and tried to start OVS it crashed:
#0 eth_compose (b=b at entry=0x7ffebedf7b00, eth_dst=..., eth_src=...,
eth_type=<optimized out>, size=size at entry=0) at lib/packets.c:965
#1 0x000000000074bfda in flow_compose (p=p at entry=0x7ffebedf7b00,
flow=flow at entry=0x7ffebedf7860, l7=l7 at entry=0x0, l7_len=l7_len at entry=64)
at lib/flow.c:2960
#2 0x00000000006f2094 in check_ct_eventmask (backer=<optimized out>) at
ofproto/ofproto-dpif.c:1233
#3 0x00000000006fb15b in check_support (backer=0x283bd20) at
ofproto/ofproto-dpif.c:1398
#4 open_dpif_backer (backerp=0x283ac38, type=0x283a290 "netdev") at
ofproto/ofproto-dpif.c:788
#5 construct (ofproto_=0x283a9f0) at ofproto/ofproto-dpif.c:1423
#6 0x00000000006e5f05 in ofproto_create (datapath_name=0x283dee0
"ovs_pvp_br0", datapath_type=<optimized out>,
ofprotop=ofprotop at entry=0x283a3f8) at ofproto/ofproto.c:545
#7 0x00000000006d7ec1 in bridge_reconfigure
(ovs_cfg=ovs_cfg at entry=0x2835530) at vswitchd/bridge.c:648
#8 0x00000000006db406 in bridge_run () at vswitchd/bridge.c:3022
I traced it back to patch "RFC v7 05/13] dp-packet: Handle multi-seg
mbufs in helper funcs".
My config is straightforward and the feature was not yet enabled:
$ ovs-vsctl show
31cca486-0451-4a51-90b8-43c11e0548e5
Bridge "ovs_pvp_br0"
Port "ovs_pvp_br0"
Interface "ovs_pvp_br0"
type: internal
Port "dpdk0"
Interface "dpdk0"
type: dpdk
options: {dpdk-devargs="0000:05:00.0", n_rxq="2"}
Port "vhost0"
Interface "vhost0"
type: dpdkvhostuserclient
options: {n_rxq="2", vhost-server-path="/tmp/vhost-sock0"}
Port "dpdk1"
Interface "dpdk1"
type: dpdk
options: {dpdk-devargs="0000:05:00.1", n_rxq="2"}
ovs_version: "2.9.90"
My goal for reviewing this part was to get a better understanding of the
dp_packet layer, so rather than spending time before reporting, I
decided to send a reply right away.
In addition are you planning on sending a v8 soon? If so I might delay
the reviewing a bit ;)
Cheers,
Eelco
On 23/05/18 18:47, Tiago Lam wrote:
> Overview
> ========
> This patchset introduces support for multi-segment mbufs to OvS-DPDK.
> Multi-segment mbufs are typically used when the size of an mbuf is
> insufficient to contain the entirety of a packet's data. Instead, the
> data is split across numerous mbufs, each carrying a portion, or
> 'segment', of the packet data. mbufs are chained via their 'next'
> attribute (an mbuf pointer).
>
> Use Cases
> =========
> i. Handling oversized (guest-originated) frames, which are marked
> for hardware accelration/offload (TSO, for example).
>
> Packets which originate from a non-DPDK source may be marked for
> offload; as such, they may be larger than the permitted ingress
> interface's MTU, and may be stored in an oversized dp-packet. In
> order to transmit such packets over a DPDK port, their contents
> must be copied to a DPDK mbuf (via dpdk_do_tx_copy). However, in
> its current implementation, that function only copies data into
> a single mbuf; if the space available in the mbuf is exhausted,
> but not all packet data has been copied, then it is lost.
> Similarly, when cloning a DPDK mbuf, it must be considered
> whether that mbuf contains multiple segments. Both issues are
> resolved within this patchset.
>
> ii. Handling jumbo frames.
>
> While OvS already supports jumbo frames, it does so by increasing
> mbuf size, such that the entirety of a jumbo frame may be handled
> in a single mbuf. This is certainly the preferred, and most
> performant approach (and remains the default). However, it places
> high demands on system memory; multi-segment mbufs may be
> prefereable for systems which are memory-constrained.
>
> Enabling multi-segment mbufs
> ============================
> Multi-segment and single-segment mbufs are mutually exclusive, and the
> user must decide on which approach to adopt on init. The introduction
> of a new OVSDB field, 'dpdk-multi-seg-mbufs', facilitates this.
>
> This is a global boolean value, which determines how jumbo frames are
> represented across all DPDK ports. In the absence of a user-supplied
> value, 'dpdk-multi-seg-mbufs' defaults to false, i.e. multi-segment
> mbufs must be explicitly enabled / single-segment mbufs remain the
> default.
>
> Setting the field is identical to setting existing DPDK-specific OVSDB
> fields:
>
> ovs-vsctl set Open_vSwitch . other_config:dpdk-init=true
> ovs-vsctl set Open_vSwitch . other_config:dpdk-lcore-mask=0x10
> ovs-vsctl set Open_vSwitch . other_config:dpdk-socket-mem=4096,0
> ==> ovs-vsctl set Open_vSwitch . other_config:dpdk-multi-seg-mbufs=true
>
> ---
>
> v7: - Rebase on master 5e720da ("erspan: fix invalid erspan version.");
> - Address Ilya comments;
> - Fix non-DPDK build;
> - Serialise the access of non pmds to allocation and free of mbufs by
> using a newly introduced mutex.
> - Add a new set of tests that integrates with the recently added DPDK
> testsuite. These focus on allocating dp_packets, with a single or
> multiple mbufs, from an instantiated mempool and performing several
> operations on those, verifying if the data at the end matches what's
> expected;
> - Fix bugs found by the new tests:
> - dp_packet_shift() wasn't taking into account shift lefts;
> - dp_packet_resize__() was misusing and miscalculating the tailrooms
> and headrooms, ending up calculating the wrong number of segments
> that needed allocation;
> - An mbuf's end was being miscalculated both in dp_packet_tail,
> dp_packet_mbuf_tail() and dp_packet_end();
> - dp_packet_set_size() was not updating the number of chained segments
> 'nb_segs';
> - Add support for multi-seg mbufs in dp_packet_clear().
>
> v6: - Rebase on master 7c0cb29 ("conntrack-tcp: Handle tcp session
> reuse.");
> - Further improve dp_packet_put_uninit() and dp_packet_shift() to
> support multi-seg mbufs;
> - Add support for multi-seg mbufs in dp_packet_l4_size() and
> improve other helper funcs, such as dp_packet_tail() and dp_
> packet_tailroom().
> - Add support for multi-seg mbufs in dp_packet_put(), dp_packet_
> put_zeros(), as well as dp_packet_resize__() - allocating new
> mbufs and linking them together;
> Restructured patchset:
> - Squash patch 5 into patch 6, since they were both related to
> copying data while handling multi-seg mbufs;
> - Split patch 4 into two separate patches - one that introduces the
> changes in helper functions to deal with multi-seg mbufs and
> two others for the shift() and put_uninit() functionality;
> - Move patch 4 to before patch 3, so that ihelper functions come
> before functionality improvement that rely on those helpers.
>
> v5: - Rebased on master e5e22dc ("datapath-windows: Prevent ct-counters
> from getting redundantly incremented");
> - Sugesh's comments have been addressed:
> - Changed dp_packet_set_data() and dp_packet_set_size() logic to
> make them independent of each other;
> - Dropped patch 3 now that dp_packet_set_data() and dp_packet_set_
> size() are independent;
> - dp_packet_clone_with_headroom() now has split functions for
> handling DPDK sourced packets and non-DPDK packets;
> - Modified various functions in dp-packet.h to account for multi-seg
> mbufs - dp_packet_put_uninit(), dp_packet_tail(), dp_packet_tail()
> and dp_packet_at();
> - Added support for shifting packet data in multi-seg mbufs, using
> dp_packet_shift();
> - Fixed some minor inconsistencies.
>
> Note that some of the changes in v5 have been contributed by Mark
> Kavanagh as well.
>
> v4: - restructure patchset
> - account for 128B ARM cacheline when sizing mbufs
>
> Mark Kavanagh (4):
> netdev-dpdk: fix mbuf sizing
> dp-packet: Init specific mbuf fields.
> netdev-dpdk: copy large packet to multi-seg. mbufs
> netdev-dpdk: support multi-segment jumbo frames
>
> Michael Qiu (1):
> dp-packet: copy data from multi-seg. DPDK mbuf
>
> Tiago Lam (8):
> dp-packet: Fix allocated size on DPDK init.
> dp-packet: Fix data_len handling multi-seg mbufs.
> dp-packet: Handle multi-seg mbufs in helper funcs.
> dp-packet: Handle multi-seg mbufs in put*() funcs.
> dp-packet: Handle multi-seg mubfs in shift() func.
> netdev-dpdk: Serialise non-pmds mbufs' alloc/free.
> dp-packet: Handle multi-seg mbufs in resize__().
> dpdk-tests: Add test coverage for multi-seg mbufs.
>
> NEWS | 1 +
> lib/dp-packet.c | 360 +++++++++++++++++++++++++++++++---
> lib/dp-packet.h | 328 +++++++++++++++++++++++++------
> lib/dpdk.c | 7 +
> lib/netdev-dpdk.c | 211 +++++++++++++++++---
> lib/netdev-dpdk.h | 5 +
> tests/automake.mk | 10 +-
> tests/dpdk-packet-mbufs.at | 7 +
> tests/system-dpdk-testsuite.at | 1 +
> tests/test-dpdk-mbufs.c | 434 +++++++++++++++++++++++++++++++++++++++++
> vswitchd/vswitch.xml | 20 ++
> 11 files changed, 1262 insertions(+), 122 deletions(-)
> create mode 100644 tests/dpdk-packet-mbufs.at
> create mode 100644 tests/test-dpdk-mbufs.c
>
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