Lines Matching full:queue
28 (multi-queue). On reception, a NIC can send different packets to different
32 queue, which in turn can be processed by separate CPUs. This mechanism is
35 Multi-queue distribution can also be used for traffic prioritization, but
42 stores a queue number. The receive queue for a packet is determined
51 both directions of the flow to land on the same Rx queue (and CPU). The
64 can be directed to their own receive queue. Such “n-tuple” filters can
71 The driver for a multi-queue capable NIC typically provides a kernel
74 num_queues. A typical RSS configuration would be to have one receive queue
79 The indirection table of an RSS device, which resolves a queue by masked
91 Each receive queue has a separate IRQ associated with it. The NIC triggers
92 this to notify a CPU when new packets arrive on the given queue. The
109 decreases queue length. For low latency networking, the optimal setting
113 receive queue overflows due to a saturated CPU, because in default
115 interrupts (and thus work) grows with each additional queue.
171 Whereas RSS selects the queue and hence CPU that will run the hardware
174 on the desired CPU’s backlog queue and waking up the CPU for processing.
185 selects the queue that should process a packet.
197 Each receive hardware queue has an associated list of CPUs to which
201 and the packet is queued to the tail of that CPU’s backlog queue. At
203 packets have been queued to their backlog queue. The IPI wakes backlog
214 can be configured for each receive queue using a sysfs file entry::
227 For a single queue device, a typical RPS configuration would be to set
233 For a multi-queue system, if RSS is configured so that a hardware
234 receive queue is mapped to each CPU, then RPS is probably redundant
236 RPS might be beneficial if the rps_cpus for each queue are the ones that
237 share the same memory domain as the interrupting CPU for that queue.
255 queue exceeds half the maximum queue length (as set by sysctl
260 dropped once the input packet queue reaches netdev_max_backlog.
261 No packets are dropped when the input packet queue length is below
298 The feature depends on the input packet queue length to exceed
336 receive queue of each device. Each table value stores a CPU index and a
346 queue has a head counter that is incremented on dequeue. A tail counter
347 is computed as head counter + queue length. In other words, the counter
355 and the rps_dev_flow table of the queue that the packet was received on
362 - The current CPU's queue head counter >= the recorded tail counter
383 The number of entries in the per-queue flow table are set through::
391 Both of these need to be set before RFS is enabled for a receive queue.
398 For a single queue device, the rps_flow_cnt value for the single queue
400 For a multi-queue device, the rps_flow_cnt for each queue might be
403 are 16 configured receive queues, rps_flow_cnt for each queue might be
420 queue for packets matching a particular flow. The network stack
425 The hardware queue for a flow is derived from the CPU recorded in
426 rps_dev_flow_table. The stack consults a CPU to hardware queue map which
430 to populate the map. For each CPU, the corresponding queue in the map is
441 configured for each receive queue by the driver, so no additional
456 which transmit queue to use when transmitting a packet on a multi-queue
458 a mapping of CPU to hardware queue(s) or a mapping of receive queue(s)
459 to hardware transmit queue(s).
466 provides two benefits. First, contention on the device queue lock is
467 significantly reduced since fewer CPUs contend for the same queue
469 transmit queue). Secondly, cache miss rate on transmit completion is
475 This mapping is used to pick transmit queue based on the receive
476 queue(s) map configuration set by the administrator. A set of receive
479 on the same queue associations for transmit and receive. This is useful for
483 received on a single queue. The receive queue number is cached in the
485 transmit queue corresponding to the associated receive queue has benefits
487 the same queue-association that a given application is polling on. This
493 XPS is configured per transmit queue by setting a bitmap of
494 CPUs/receive-queues that may use that queue to transmit. The reverse
498 called to select a queue. This function uses the ID of the receive queue
499 for the socket connection for a match in the receive queue-to-transmit queue
501 running CPU as a key into the CPU-to-queue lookup table. If the
502 ID matches a single queue, that is used for transmission. If multiple
504 into the set. When selecting the transmit queue based on receive queue(s)
508 The queue chosen for transmitting a particular flow is saved in the
510 This transmit queue is used for subsequent packets sent on the flow to
513 ooo packets, the queue for a flow can subsequently only be changed if
515 there are no outstanding packets in the flow, so the transmit queue can
527 to transmit queue can be inspected and configured using sysfs:
541 For a network device with a single transmission queue, XPS configuration
542 has no effect, since there is no choice in this case. In a multi-queue
543 system, XPS is preferably configured so that each CPU maps onto one queue.
545 queue can also map onto one CPU, resulting in exclusive pairings that
547 best CPUs to share a given queue are probably those that share the cache
548 with the CPU that processes transmit completions for that queue
551 For transmit queue selection based on receive queue(s), XPS has to be
552 explicitly configured mapping receive-queue(s) to transmit queue(s). If the
553 user configuration for receive-queue map does not apply, then the transmit
554 queue is selected based on the CPUs map.
557 Per TX Queue rate limitation