Hi Mark,
Thanks for addressing the comments. The patch looks good to me and I plan to test it tomorrow. fbl On Wed, Jun 30, 2021 at 05:53:49AM -0400, Mark Gray wrote: > The Open vSwitch kernel module uses the upcall mechanism to send > packets from kernel space to user space when it misses in the kernel > space flow table. The upcall sends packets via a Netlink socket. > Currently, a Netlink socket is created for every vport. In this way, > there is a 1:1 mapping between a vport and a Netlink socket. > When a packet is received by a vport, if it needs to be sent to > user space, it is sent via the corresponding Netlink socket. > > This mechanism, with various iterations of the corresponding user > space code, has seen some limitations and issues: > > * On systems with a large number of vports, there is a correspondingly > large number of Netlink sockets which can limit scaling. > (https://bugzilla.redhat.com/show_bug.cgi?id=1526306) > * Packet reordering on upcalls. > (https://bugzilla.redhat.com/show_bug.cgi?id=1844576) > * A thundering herd issue. > (https://bugzilla.redhat.com/show_bug.cgi?id=1834444) > > This patch introduces an alternative, feature-negotiated, upcall > mode using a per-cpu dispatch rather than a per-vport dispatch. > > In this mode, the Netlink socket to be used for the upcall is > selected based on the CPU of the thread that is executing the upcall. > In this way, it resolves the issues above as: > > a) The number of Netlink sockets scales with the number of CPUs > rather than the number of vports. > b) Ordering per-flow is maintained as packets are distributed to > CPUs based on mechanisms such as RSS and flows are distributed > to a single user space thread. > c) Packets from a flow can only wake up one user space thread. > > The corresponding user space code can be found at: > https://mail.openvswitch.org/pipermail/ovs-dev/2021-April/382618.html > > Bugzilla: https://bugzilla.redhat.com/1844576 > Signed-off-by: Mark Gray <mark.d.g...@redhat.com> > --- > > Notes: > v1 - Reworked based on Flavio's comments: > * Fixed handling of userspace action case > * Renamed 'struct dp_portids' > * Fixed handling of return from kmalloc() > * Removed check for dispatch type from ovs_dp_get_upcall_portid() > - Reworked based on Dan's comments: > * Fixed handling of return from kmalloc() > - Reworked based on Pravin's comments: > * Fixed handling of userspace action case > - Added kfree() in destroy_dp_rcu() to cleanup netlink port ids > > include/uapi/linux/openvswitch.h | 8 ++++ > net/openvswitch/actions.c | 6 ++- > net/openvswitch/datapath.c | 70 +++++++++++++++++++++++++++++++- > net/openvswitch/datapath.h | 20 +++++++++ > 4 files changed, 101 insertions(+), 3 deletions(-) > > diff --git a/include/uapi/linux/openvswitch.h > b/include/uapi/linux/openvswitch.h > index 8d16744edc31..6571b57b2268 100644 > --- a/include/uapi/linux/openvswitch.h > +++ b/include/uapi/linux/openvswitch.h > @@ -70,6 +70,8 @@ enum ovs_datapath_cmd { > * set on the datapath port (for OVS_ACTION_ATTR_MISS). Only valid on > * %OVS_DP_CMD_NEW requests. A value of zero indicates that upcalls should > * not be sent. > + * OVS_DP_ATTR_PER_CPU_PIDS: Per-cpu array of PIDs for upcalls when > + * OVS_DP_F_DISPATCH_UPCALL_PER_CPU feature is set. > * @OVS_DP_ATTR_STATS: Statistics about packets that have passed through the > * datapath. Always present in notifications. > * @OVS_DP_ATTR_MEGAFLOW_STATS: Statistics about mega flow masks usage for > the > @@ -87,6 +89,9 @@ enum ovs_datapath_attr { > OVS_DP_ATTR_USER_FEATURES, /* OVS_DP_F_* */ > OVS_DP_ATTR_PAD, > OVS_DP_ATTR_MASKS_CACHE_SIZE, > + OVS_DP_ATTR_PER_CPU_PIDS, /* Netlink PIDS to receive upcalls in > per-cpu > + * dispatch mode > + */ > __OVS_DP_ATTR_MAX > }; > > @@ -127,6 +132,9 @@ struct ovs_vport_stats { > /* Allow tc offload recirc sharing */ > #define OVS_DP_F_TC_RECIRC_SHARING (1 << 2) > > +/* Allow per-cpu dispatch of upcalls */ > +#define OVS_DP_F_DISPATCH_UPCALL_PER_CPU (1 << 3) > + > /* Fixed logical ports. */ > #define OVSP_LOCAL ((__u32)0) > > diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c > index ef15d9eb4774..f79679746c62 100644 > --- a/net/openvswitch/actions.c > +++ b/net/openvswitch/actions.c > @@ -924,7 +924,11 @@ static int output_userspace(struct datapath *dp, struct > sk_buff *skb, > break; > > case OVS_USERSPACE_ATTR_PID: > - upcall.portid = nla_get_u32(a); > + if (dp->user_features & > OVS_DP_F_DISPATCH_UPCALL_PER_CPU) > + upcall.portid = > + ovs_dp_get_upcall_portid(dp, > smp_processor_id()); > + else > + upcall.portid = nla_get_u32(a); > break; > > case OVS_USERSPACE_ATTR_EGRESS_TUN_PORT: { > diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c > index bc164b35e67d..8d54fa323543 100644 > --- a/net/openvswitch/datapath.c > +++ b/net/openvswitch/datapath.c > @@ -166,6 +166,7 @@ static void destroy_dp_rcu(struct rcu_head *rcu) > free_percpu(dp->stats_percpu); > kfree(dp->ports); > ovs_meters_exit(dp); > + kfree(dp->upcall_portids); > kfree(dp); > } > > @@ -239,7 +240,12 @@ void ovs_dp_process_packet(struct sk_buff *skb, struct > sw_flow_key *key) > > memset(&upcall, 0, sizeof(upcall)); > upcall.cmd = OVS_PACKET_CMD_MISS; > - upcall.portid = ovs_vport_find_upcall_portid(p, skb); > + > + if (dp->user_features & OVS_DP_F_DISPATCH_UPCALL_PER_CPU) > + upcall.portid = ovs_dp_get_upcall_portid(dp, > smp_processor_id()); > + else > + upcall.portid = ovs_vport_find_upcall_portid(p, skb); > + > upcall.mru = OVS_CB(skb)->mru; > error = ovs_dp_upcall(dp, skb, key, &upcall, 0); > if (unlikely(error)) > @@ -1594,16 +1600,67 @@ static void ovs_dp_reset_user_features(struct sk_buff > *skb, > > DEFINE_STATIC_KEY_FALSE(tc_recirc_sharing_support); > > +int ovs_dp_set_upcall_portids(struct datapath *dp, > + const struct nlattr *ids) > +{ > + struct dp_nlsk_pids *old, *dp_nlsk_pids; > + > + if (!nla_len(ids) || nla_len(ids) % sizeof(u32)) > + return -EINVAL; > + > + old = ovsl_dereference(dp->upcall_portids); > + > + dp_nlsk_pids = kmalloc(sizeof(*dp_nlsk_pids) + nla_len(ids), > + GFP_KERNEL); > + if (!dp_nlsk_pids) > + return -ENOMEM; > + > + dp_nlsk_pids->n_pids = nla_len(ids) / sizeof(u32); > + nla_memcpy(dp_nlsk_pids->pids, ids, nla_len(ids)); > + > + rcu_assign_pointer(dp->upcall_portids, dp_nlsk_pids); > + > + kfree_rcu(old, rcu); > + > + return 0; > +} > + > +u32 ovs_dp_get_upcall_portid(const struct datapath *dp, uint32_t cpu_id) > +{ > + struct dp_nlsk_pids *dp_nlsk_pids; > + > + dp_nlsk_pids = rcu_dereference_ovsl(dp->upcall_portids); > + > + if (dp_nlsk_pids) { > + if (cpu_id < dp_nlsk_pids->n_pids) { > + return dp_nlsk_pids->pids[cpu_id]; > + } else if (dp_nlsk_pids->n_pids > 0 && cpu_id >= > dp_nlsk_pids->n_pids) { > + /* If the number of netlink PIDs is mismatched with the > number of > + * CPUs as seen by the kernel, log this and send the > upcall to an > + * arbitrary socket (0) in order to not drop packets > + */ > + pr_info_ratelimited("cpu_id mismatch with handler > threads"); > + return dp_nlsk_pids->pids[cpu_id % > dp_nlsk_pids->n_pids]; > + } else { > + return 0; > + } > + } else { > + return 0; > + } > +} > + > static int ovs_dp_change(struct datapath *dp, struct nlattr *a[]) > { > u32 user_features = 0; > + int err; > > if (a[OVS_DP_ATTR_USER_FEATURES]) { > user_features = nla_get_u32(a[OVS_DP_ATTR_USER_FEATURES]); > > if (user_features & ~(OVS_DP_F_VPORT_PIDS | > OVS_DP_F_UNALIGNED | > - OVS_DP_F_TC_RECIRC_SHARING)) > + OVS_DP_F_TC_RECIRC_SHARING | > + OVS_DP_F_DISPATCH_UPCALL_PER_CPU)) > return -EOPNOTSUPP; > > #if !IS_ENABLED(CONFIG_NET_TC_SKB_EXT) > @@ -1624,6 +1681,15 @@ static int ovs_dp_change(struct datapath *dp, struct > nlattr *a[]) > > dp->user_features = user_features; > > + if (dp->user_features & OVS_DP_F_DISPATCH_UPCALL_PER_CPU && > + a[OVS_DP_ATTR_PER_CPU_PIDS]) { > + /* Upcall Netlink Port IDs have been updated */ > + err = ovs_dp_set_upcall_portids(dp, > + a[OVS_DP_ATTR_PER_CPU_PIDS]); > + if (err) > + return err; > + } > + > if (dp->user_features & OVS_DP_F_TC_RECIRC_SHARING) > static_branch_enable(&tc_recirc_sharing_support); > else > diff --git a/net/openvswitch/datapath.h b/net/openvswitch/datapath.h > index 38f7d3e66ca6..a12a7d0168b1 100644 > --- a/net/openvswitch/datapath.h > +++ b/net/openvswitch/datapath.h > @@ -50,6 +50,21 @@ struct dp_stats_percpu { > struct u64_stats_sync syncp; > }; > > +/** > + * struct dp_nlsk_pids - array of netlink portids of for a datapath. > + * This is used when OVS_DP_F_DISPATCH_UPCALL_PER_CPU > + * is enabled and must be protected by rcu. > + * @rcu: RCU callback head for deferred destruction. > + * @n_pids: Size of @pids array. > + * @pids: Array storing the Netlink socket PIDs indexed by CPU ID for packets > + * that miss the flow table. > + */ > +struct dp_nlsk_pids { > + struct rcu_head rcu; > + u32 n_pids; > + u32 pids[]; > +}; > + > /** > * struct datapath - datapath for flow-based packet switching > * @rcu: RCU callback head for deferred destruction. > @@ -61,6 +76,7 @@ struct dp_stats_percpu { > * @net: Reference to net namespace. > * @max_headroom: the maximum headroom of all vports in this datapath; it > will > * be used by all the internal vports in this dp. > + * @upcall_portids: RCU protected 'struct dp_nlsk_pids'. > * > * Context: See the comment on locking at the top of datapath.c for > additional > * locking information. > @@ -87,6 +103,8 @@ struct datapath { > > /* Switch meters. */ > struct dp_meter_table meter_tbl; > + > + struct dp_nlsk_pids __rcu *upcall_portids; > }; > > /** > @@ -243,6 +261,8 @@ int ovs_dp_upcall(struct datapath *, struct sk_buff *, > const struct sw_flow_key *, const struct dp_upcall_info *, > uint32_t cutlen); > > +u32 ovs_dp_get_upcall_portid(const struct datapath *dp, uint32_t cpu_id); > +int ovs_dp_set_upcall_portids(struct datapath *dp, const struct nlattr *ids); > const char *ovs_dp_name(const struct datapath *dp); > struct sk_buff *ovs_vport_cmd_build_info(struct vport *vport, struct net > *net, > u32 portid, u32 seq, u8 cmd); > -- > 2.27.0 > -- fbl _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev
