Lines Matching +full:multi +full:- +full:function

1 .. SPDX-License-Identifier: GPL-2.0
13 multi-processor systems.
17 - RSS: Receive Side Scaling
18 - RPS: Receive Packet Steering
19 - RFS: Receive Flow Steering
20 - Accelerated Receive Flow Steering
21 - XPS: Transmit Packet Steering
28 (multi-queue). On reception, a NIC can send different packets to different
33 generally known as “Receive-side Scaling” (RSS). The goal of RSS and
35 Multi-queue distribution can also be used for traffic prioritization, but
38 The filter used in RSS is typically a hash function over the network
39 and/or transport layer headers-- for example, a 4-tuple hash over
41 implementation of RSS uses a 128-entry indirection table where each entry
49 can be directed to their own receive queue. Such “n-tuple” filters can
50 be configured from ethtool (--config-ntuple).
54 -----------------
56 The driver for a multi-queue capable NIC typically provides a kernel
68 commands (--show-rxfh-indir and --set-rxfh-indir). Modifying the
78 signaling path for PCIe devices uses message signaled interrupts (MSI-X),
81 an IRQ may be handled on any CPU. Because a non-negligible part of packet
84 affinity of each interrupt see Documentation/core-api/irq/irq-affinity.rst. Some systems
96 NIC maximum, if lower). The most efficient high-rate configuration
102 Per-cpu load can be observed using the mpstat utility, but note that on
123    introduce inter-processor interrupts (IPIs))
127 netif_receive_skb(). These call the get_rps_cpu() function, which
131 flow hash over the packet’s addresses or ports (2-tuple or 4-tuple hash
137 skb->hash and can be used elsewhere in the stack as a hash of the
152 -----------------
159   /sys/class/net/<dev>/queues/rx-<n>/rps_cpus
163 CPU. Documentation/core-api/irq/irq-affinity.rst explains how CPUs are assigned to
176 For a multi-queue system, if RSS is configured so that a hardware
184 --------------
187 reordering. The trade-off to sending all packets from the same flow
199 net.core.netdev_max_backlog), the kernel starts a per-flow packet
220 Per-flow rate is calculated by hashing each packet into a hashtable
221 bucket and incrementing a per-bucket counter. The hash function is
223 be much larger than the number of CPUs, flow limit has finer-grained
305   - The current CPU's queue head counter >= the recorded tail counter
307   - The current CPU is unset (>= nr_cpu_ids)
308   - The current CPU is offline
318 -----------------
326 The number of entries in the per-queue flow table are set through::
328   /sys/class/net/<dev>/queues/rx-<n>/rps_flow_cnt
343 For a multi-queue device, the rps_flow_cnt for each queue might be
353 Accelerated RFS is to RFS what RSS is to RPS: a hardware-accelerated load
362 ndo_rx_flow_steer driver function to communicate the desired hardware
364 automatically calls this function every time a flow entry in
370 is maintained by the NIC driver. This is an auto-generated reverse map of
378 -----------------------------
399 which transmit queue to use when transmitting a packet on a multi-queue
423 busy polling multi-threaded workloads where there are challenges in
430 the same queue-association that a given application is polling on. This
437 CPUs/receive-queues that may use that queue to transmit. The reverse
438 mapping, from CPUs to transmit queues or from receive-queues to transmit
440 transmitting the first packet in a flow, the function get_xps_queue() is
441 called to select a queue. This function uses the ID of the receive queue
442 for the socket connection for a match in the receive queue-to-transmit queue
443 lookup table. Alternatively, this function can also use the ID of the
444 running CPU as a key into the CPU-to-queue lookup table. If the
457 skb->ooo_okay is set for a packet in the flow. This flag indicates that
465 -----------------
469 how, XPS is configured at device init. The mapping of CPUs/receive-queues
474   /sys/class/net/<dev>/queues/tx-<n>/xps_cpus
476 For selection based on receive-queues map::
478   /sys/class/net/<dev>/queues/tx-<n>/xps_rxqs
485 has no effect, since there is no choice in this case. In a multi-queue
495 explicitly configured mapping receive-queue(s) to transmit queue(s). If the
496 user configuration for receive-queue map does not apply, then the transmit
503 These are rate-limitation mechanisms implemented by HW, where currently
504 a max-rate attribute is supported, by setting a Mbps value to::
506   /sys/class/net/<dev>/queues/tx-<n>/tx_maxrate
522 - Tom Herbert (therbert@google.com)
523 - Willem de Bruijn (willemb@google.com)