From 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 21 Feb 2023 18:24:12 -0800 Subject: Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next Pull networking updates from Jakub Kicinski: "Core: - Add dedicated kmem_cache for typical/small skb->head, avoid having to access struct page at kfree time, and improve memory use. - Introduce sysctl to set default RPS configuration for new netdevs. - Define Netlink protocol specification format which can be used to describe messages used by each family and auto-generate parsers. Add tools for generating kernel data structures and uAPI headers. - Expose all net/core sysctls inside netns. - Remove 4s sleep in netpoll if carrier is instantly detected on boot. - Add configurable limit of MDB entries per port, and port-vlan. - Continue populating drop reasons throughout the stack. - Retire a handful of legacy Qdiscs and classifiers. Protocols: - Support IPv4 big TCP (TSO frames larger than 64kB). - Add IP_LOCAL_PORT_RANGE socket option, to control local port range on socket by socket basis. - Track and report in procfs number of MPTCP sockets used. - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path manager. - IPv6: don't check net.ipv6.route.max_size and rely on garbage collection to free memory (similarly to IPv4). - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986). - ICMP: add per-rate limit counters. - Add support for user scanning requests in ieee802154. - Remove static WEP support. - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate reporting. - WiFi 7 EHT channel puncturing support (client & AP). BPF: - Add a rbtree data structure following the "next-gen data structure" precedent set by recently added linked list, that is, by using kfunc + kptr instead of adding a new BPF map type. - Expose XDP hints via kfuncs with initial support for RX hash and timestamp metadata. - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to better support decap on GRE tunnel devices not operating in collect metadata. - Improve x86 JIT's codegen for PROBE_MEM runtime error checks. - Remove the need for trace_printk_lock for bpf_trace_printk and bpf_trace_vprintk helpers. - Extend libbpf's bpf_tracing.h support for tracing arguments of kprobes/uprobes and syscall as a special case. - Significantly reduce the search time for module symbols by livepatch and BPF. - Enable cpumasks to be used as kptrs, which is useful for tracing programs tracking which tasks end up running on which CPUs in different time intervals. - Add support for BPF trampoline on s390x and riscv64. - Add capability to export the XDP features supported by the NIC. - Add __bpf_kfunc tag for marking kernel functions as kfuncs. - Add cgroup.memory=nobpf kernel parameter option to disable BPF memory accounting for container environments. Netfilter: - Remove the CLUSTERIP target. It has been marked as obsolete for years, and we still have WARN splats wrt races of the out-of-band /proc interface installed by this target. - Add 'destroy' commands to nf_tables. They are identical to the existing 'delete' commands, but do not return an error if the referenced object (set, chain, rule...) did not exist. Driver API: - Improve cpumask_local_spread() locality to help NICs set the right IRQ affinity on AMD platforms. - Separate C22 and C45 MDIO bus transactions more clearly. - Introduce new DCB table to control DSCP rewrite on egress. - Support configuration of Physical Layer Collision Avoidance (PLCA) Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of shared medium Ethernet. - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing preemption of low priority frames by high priority frames. - Add support for controlling MACSec offload using netlink SET. - Rework devlink instance refcounts to allow registration and de-registration under the instance lock. Split the code into multiple files, drop some of the unnecessarily granular locks and factor out common parts of netlink operation handling. - Add TX frame aggregation parameters (for USB drivers). - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning messages with notifications for debug. - Allow offloading of UDP NEW connections via act_ct. - Add support for per action HW stats in TC. - Support hardware miss to TC action (continue processing in SW from a specific point in the action chain). - Warn if old Wireless Extension user space interface is used with modern cfg80211/mac80211 drivers. Do not support Wireless Extensions for Wi-Fi 7 devices at all. Everyone should switch to using nl80211 interface instead. - Improve the CAN bit timing configuration. Use extack to return error messages directly to user space, update the SJW handling, including the definition of a new default value that will benefit CAN-FD controllers, by increasing their oscillator tolerance. New hardware / drivers: - Ethernet: - nVidia BlueField-3 support (control traffic driver) - Ethernet support for imx93 SoCs - Motorcomm yt8531 gigabit Ethernet PHY - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA) - Microchip LAN8841 PHY (incl. cable diagnostics and PTP) - Amlogic gxl MDIO mux - WiFi: - RealTek RTL8188EU (rtl8xxxu) - Qualcomm Wi-Fi 7 devices (ath12k) - CAN: - Renesas R-Car V4H Drivers: - Bluetooth: - Set Per Platform Antenna Gain (PPAG) for Intel controllers. - Ethernet NICs: - Intel (1G, igc): - support TSN / Qbv / packet scheduling features of i226 model - Intel (100G, ice): - use GNSS subsystem instead of TTY - multi-buffer XDP support - extend support for GPIO pins to E823 devices - nVidia/Mellanox: - update the shared buffer configuration on PFC commands - implement PTP adjphase function for HW offset control - TC support for Geneve and GRE with VF tunnel offload - more efficient crypto key management method - multi-port eswitch support - Netronome/Corigine: - add DCB IEEE support - support IPsec offloading for NFP3800 - Freescale/NXP (enetc): - support XDP_REDIRECT for XDP non-linear buffers - improve reconfig, avoid link flap and waiting for idle - support MAC Merge layer - Other NICs: - sfc/ef100: add basic devlink support for ef100 - ionic: rx_push mode operation (writing descriptors via MMIO) - bnxt: use the auxiliary bus abstraction for RDMA - r8169: disable ASPM and reset bus in case of tx timeout - cpsw: support QSGMII mode for J721e CPSW9G - cpts: support pulse-per-second output - ngbe: add an mdio bus driver - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing - r8152: handle devices with FW with NCM support - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation - virtio-net: support multi buffer XDP - virtio/vsock: replace virtio_vsock_pkt with sk_buff - tsnep: XDP support - Ethernet high-speed switches: - nVidia/Mellanox (mlxsw): - add support for latency TLV (in FW control messages) - Microchip (sparx5): - separate explicit and implicit traffic forwarding rules, make the implicit rules always active - add support for egress DSCP rewrite - IS0 VCAP support (Ingress Classification) - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS etc.) - ES2 VCAP support (Egress Access Control) - support for Per-Stream Filtering and Policing (802.1Q, 8.6.5.1) - Ethernet embedded switches: - Marvell (mv88e6xxx): - add MAB (port auth) offload support - enable PTP receive for mv88e6390 - NXP (ocelot): - support MAC Merge layer - support for the the vsc7512 internal copper phys - Microchip: - lan9303: convert to PHYLINK - lan966x: support TC flower filter statistics - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x - lan937x: support Credit Based Shaper configuration - ksz9477: support Energy Efficient Ethernet - other: - qca8k: convert to regmap read/write API, use bulk operations - rswitch: Improve TX timestamp accuracy - Intel WiFi (iwlwifi): - EHT (Wi-Fi 7) rate reporting - STEP equalizer support: transfer some STEP (connection to radio on platforms with integrated wifi) related parameters from the BIOS to the firmware. - Qualcomm 802.11ax WiFi (ath11k): - IPQ5018 support - Fine Timing Measurement (FTM) responder role support - channel 177 support - MediaTek WiFi (mt76): - per-PHY LED support - mt7996: EHT (Wi-Fi 7) support - Wireless Ethernet Dispatch (WED) reset support - switch to using page pool allocator - RealTek WiFi (rtw89): - support new version of Bluetooth co-existance - Mobile: - rmnet: support TX aggregation" * tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits) page_pool: add a comment explaining the fragment counter usage net: ethtool: fix __ethtool_dev_mm_supported() implementation ethtool: pse-pd: Fix double word in comments xsk: add linux/vmalloc.h to xsk.c sefltests: netdevsim: wait for devlink instance after netns removal selftest: fib_tests: Always cleanup before exit net/mlx5e: Align IPsec ASO result memory to be as required by hardware net/mlx5e: TC, Set CT miss to the specific ct action instance net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG net/mlx5: Refactor tc miss handling to a single function net/mlx5: Kconfig: Make tc offload depend on tc skb extension net/sched: flower: Support hardware miss to tc action net/sched: flower: Move filter handle initialization earlier net/sched: cls_api: Support hardware miss to tc action net/sched: Rename user cookie and act cookie sfc: fix builds without CONFIG_RTC_LIB sfc: clean up some inconsistent indentings net/mlx4_en: Introduce flexible array to silence overflow warning net: lan966x: Fix possible deadlock inside PTP net/ulp: Remove redundant ->clone() test in inet_clone_ulp(). ... --- Documentation/networking/net_dim.rst | 176 +++++++++++++++++++++++++++++++++++ 1 file changed, 176 insertions(+) create mode 100644 Documentation/networking/net_dim.rst (limited to 'Documentation/networking/net_dim.rst') diff --git a/Documentation/networking/net_dim.rst b/Documentation/networking/net_dim.rst new file mode 100644 index 000000000..3bed9fd95 --- /dev/null +++ b/Documentation/networking/net_dim.rst @@ -0,0 +1,176 @@ +====================================================== +Net DIM - Generic Network Dynamic Interrupt Moderation +====================================================== + +:Author: Tal Gilboa + +.. contents:: :depth: 2 + +Assumptions +=========== + +This document assumes the reader has basic knowledge in network drivers +and in general interrupt moderation. + + +Introduction +============ + +Dynamic Interrupt Moderation (DIM) (in networking) refers to changing the +interrupt moderation configuration of a channel in order to optimize packet +processing. The mechanism includes an algorithm which decides if and how to +change moderation parameters for a channel, usually by performing an analysis on +runtime data sampled from the system. Net DIM is such a mechanism. In each +iteration of the algorithm, it analyses a given sample of the data, compares it +to the previous sample and if required, it can decide to change some of the +interrupt moderation configuration fields. The data sample is composed of data +bandwidth, the number of packets and the number of events. The time between +samples is also measured. Net DIM compares the current and the previous data and +returns an adjusted interrupt moderation configuration object. In some cases, +the algorithm might decide not to change anything. The configuration fields are +the minimum duration (microseconds) allowed between events and the maximum +number of wanted packets per event. The Net DIM algorithm ascribes importance to +increase bandwidth over reducing interrupt rate. + + +Net DIM Algorithm +================= + +Each iteration of the Net DIM algorithm follows these steps: + +#. Calculates new data sample. +#. Compares it to previous sample. +#. Makes a decision - suggests interrupt moderation configuration fields. +#. Applies a schedule work function, which applies suggested configuration. + +The first two steps are straightforward, both the new and the previous data are +supplied by the driver registered to Net DIM. The previous data is the new data +supplied to the previous iteration. The comparison step checks the difference +between the new and previous data and decides on the result of the last step. +A step would result as "better" if bandwidth increases and as "worse" if +bandwidth reduces. If there is no change in bandwidth, the packet rate is +compared in a similar fashion - increase == "better" and decrease == "worse". +In case there is no change in the packet rate as well, the interrupt rate is +compared. Here the algorithm tries to optimize for lower interrupt rate so an +increase in the interrupt rate is considered "worse" and a decrease is +considered "better". Step #2 has an optimization for avoiding false results: it +only considers a difference between samples as valid if it is greater than a +certain percentage. Also, since Net DIM does not measure anything by itself, it +assumes the data provided by the driver is valid. + +Step #3 decides on the suggested configuration based on the result from step #2 +and the internal state of the algorithm. The states reflect the "direction" of +the algorithm: is it going left (reducing moderation), right (increasing +moderation) or standing still. Another optimization is that if a decision +to stay still is made multiple times, the interval between iterations of the +algorithm would increase in order to reduce calculation overhead. Also, after +"parking" on one of the most left or most right decisions, the algorithm may +decide to verify this decision by taking a step in the other direction. This is +done in order to avoid getting stuck in a "deep sleep" scenario. Once a +decision is made, an interrupt moderation configuration is selected from +the predefined profiles. + +The last step is to notify the registered driver that it should apply the +suggested configuration. This is done by scheduling a work function, defined by +the Net DIM API and provided by the registered driver. + +As you can see, Net DIM itself does not actively interact with the system. It +would have trouble making the correct decisions if the wrong data is supplied to +it and it would be useless if the work function would not apply the suggested +configuration. This does, however, allow the registered driver some room for +manoeuvre as it may provide partial data or ignore the algorithm suggestion +under some conditions. + + +Registering a Network Device to DIM +=================================== + +Net DIM API exposes the main function net_dim(). +This function is the entry point to the Net +DIM algorithm and has to be called every time the driver would like to check if +it should change interrupt moderation parameters. The driver should provide two +data structures: :c:type:`struct dim ` and +:c:type:`struct dim_sample `. :c:type:`struct dim ` +describes the state of DIM for a specific object (RX queue, TX queue, +other queues, etc.). This includes the current selected profile, previous data +samples, the callback function provided by the driver and more. +:c:type:`struct dim_sample ` describes a data sample, +which will be compared to the data sample stored in :c:type:`struct dim ` +in order to decide on the algorithm's next +step. The sample should include bytes, packets and interrupts, measured by +the driver. + +In order to use Net DIM from a networking driver, the driver needs to call the +main net_dim() function. The recommended method is to call net_dim() on each +interrupt. Since Net DIM has a built-in moderation and it might decide to skip +iterations under certain conditions, there is no need to moderate the net_dim() +calls as well. As mentioned above, the driver needs to provide an object of type +:c:type:`struct dim ` to the net_dim() function call. It is advised for +each entity using Net DIM to hold a :c:type:`struct dim ` as part of its +data structure and use it as the main Net DIM API object. +The :c:type:`struct dim_sample ` should hold the latest +bytes, packets and interrupts count. No need to perform any calculations, just +include the raw data. + +The net_dim() call itself does not return anything. Instead Net DIM relies on +the driver to provide a callback function, which is called when the algorithm +decides to make a change in the interrupt moderation parameters. This callback +will be scheduled and run in a separate thread in order not to add overhead to +the data flow. After the work is done, Net DIM algorithm needs to be set to +the proper state in order to move to the next iteration. + + +Example +======= + +The following code demonstrates how to register a driver to Net DIM. The actual +usage is not complete but it should make the outline of the usage clear. + +.. code-block:: c + + #include + + /* Callback for net DIM to schedule on a decision to change moderation */ + void my_driver_do_dim_work(struct work_struct *work) + { + /* Get struct dim from struct work_struct */ + struct dim *dim = container_of(work, struct dim, + work); + /* Do interrupt moderation related stuff */ + ... + + /* Signal net DIM work is done and it should move to next iteration */ + dim->state = DIM_START_MEASURE; + } + + /* My driver's interrupt handler */ + int my_driver_handle_interrupt(struct my_driver_entity *my_entity, ...) + { + ... + /* A struct to hold current measured data */ + struct dim_sample dim_sample; + ... + /* Initiate data sample struct with current data */ + dim_update_sample(my_entity->events, + my_entity->packets, + my_entity->bytes, + &dim_sample); + /* Call net DIM */ + net_dim(&my_entity->dim, dim_sample); + ... + } + + /* My entity's initialization function (my_entity was already allocated) */ + int my_driver_init_my_entity(struct my_driver_entity *my_entity, ...) + { + ... + /* Initiate struct work_struct with my driver's callback function */ + INIT_WORK(&my_entity->dim.work, my_driver_do_dim_work); + ... + } + +Dynamic Interrupt Moderation (DIM) library API +============================================== + +.. kernel-doc:: include/linux/dim.h + :internal: -- cgit v1.2.3