What is a FIFO size?
Another rule defines the FiFo size for processes that require curing (i.e., a glue drying or a part cooling, etc.). The FiFo lane should be long enough so that the part can finish its curing process (including some safety time).
How to choose the right FIFO?
The FiFo should be able to cover failures, change-overs, or other downtimes of the processes, while at the same time be not too big and cumbersome. Adjust if the real behavior does not meet your expectations. Disappointing, isn’t it? After all this math, I just tell you to pull it out of somebody’s a**. Yet that is current industry practice.
What is the difference between TX and RX FIFO?
Hey. I don't understand the difference between TX FIFO and RX FIFO inside the Network Interface Controller (Ethernet). TX holds bits to be transmitted out. RX holds received bits that need to be read by the device. Both are temporary storages and not meant to be used to store important program data.
What determines the size of the FIFO Lane?
For example, one rule defines the FiFo lane based on the desired lead time. If you want a long lead time, simply make your FiFo larger. But then, who would want a long lead time?!?! Another rule defines the FiFo size for processes that require curing (i.e., a glue drying or a part cooling, etc.).
What is RX ring size?
The default RX Ring size is 256 (the maximum is 4096). User can increase this with the ethtool -G command.
How do I know what size NIC buffer to use?
To find out if packets were dropped, you can use the netstat and ifconfig commands. The RX-DRP column indicates the number of packets that were dropped. Set the RX value such that no packets get dropped and the RX-DRP column shows the values as 0. You might need to test several values to optimize the performance.
What is a nic queue?
NICs expose multiple circular buffers called queues or rings to transfer packets. The simplest setup uses only one receive and one transmit queue. Multiple transmit queues are merged on the NIC, incoming traffic is split according to filters or a hashing algorithm if multiple receive queues are configured.
What is transmission queue length?
The Transmit Queue Length ( txqueuelen ) is a TCP/IP stack network interface value that sets the number of packets allowed per kernel transmit queue of a network interface device. By default, the txqueuelen value for TAP interfaces is set to 1000 in the MCP Build ID 2019.2.
What is an RX buffer?
Transmit and receive buffers are used to regulate the flow of data frames between adapters and protocol stacks. Although the default settings are usually acceptable, increasing the number may improve performance if network traffic is heavy, but it will also use system memory.
What is RX and TX in ring buffer?
Ring buffers exist on both the receive (rx) and transmit (tx) side of each interface on the firewall.
What is Multiqueue NIC?
Network interface controller (NIC) multi-queue enables an ECS instance to use more than one NIC queues to improve network performance. Performance bottlenecks may occur when a single vCPU of an instance is used to process NIC interrupts.
How do I enable multi-queue NIC?
Note If the return values of the two Combined fields are the same, NIC multi-queue is enabled for the primary ENI. Run the ethtool -L eth0 combined 2 command to enable NIC multi-queue. This command configures the eth0 primary ENI to use two queues. Configure NIC multi-queue for the secondary ENI.
How do I monitor my softIRQ?
Check softIRQ stats by reading /proc/softirqs . This file can give you an idea of how your network receive ( NET_RX ) processing is currently distributed across your CPUs. If it is distributed unevenly, you will see a larger count value for some CPUs than others.
Does queuing delay depend on packet size?
Queuing delay is the time spent by the packet sitting in a queue waiting to be transmitted onto the link. The amount of time it needs to wait depends on the size of the Queue.
How is queue delay calculated?
The average delay any given packet is likely to experience is given by the formula 1/(μ-λ) where μ is the number of packets per second the facility can sustain and λ is the average rate at which packets are arriving to be serviced. This formula can be used when no packets are dropped from the queue.
How do you calculate a queue delay?
Assume a constant transmission rate of R = 300000 bps, a constant packet-length L = 1100 bits, and a is the average rate of packets/second. Traffic intensity I = La/R, and the queuing delay is calculated as I(L/R)(1 - I) for I < 1.
How to determine the size of a FiFO?
To determine the FiFo size, ask somebody familiar with the system about his opinion. The FiFo should be able to cover failures, change-overs, or other downtimes of the processes, while at the same time be not too big and cumbersome. Adjust if the real behavior does not meet your expectations.
Why are FiFO lanes important?
FiFo lanes are an important tool to establish a pull system. They are often combined with kanban. However, while there is a lot of information on how to calculate the number of kanban (the Kanban Formula ), there is very little information available on how large a FiFo should be. In my last post I talked about why we need FiFo lanes.
What is inventory in FIFo?
Inventory (as, for example, a FiFo) tries to prevent the slow down of process B. The more inventory you have, the less likely it is that process B will be slowed down by process A. This will increase the overall system output. Please note that no matter what you do with your inventory, the system cannot become faster than process B.
Is there a rule of thumb for FiFO size?
In truth, there is not really any rule of thumb. As consultants we would have used an expert estimate – which are nothing but fancy words for the gut feeling of somebody familiar with the system. Hence: To determine the FiFo size, ask somebody familiar with the system about his opinion.
Does a small buffer make a big difference?
The general trend is true, however. A small buffer makes a big difference, whereas a larger buffer will not give you as much improvement.
Is buffering a bottleneck good?
Buffering the bottleneck is sensible, since you don’t want your bottleneck to wait for other processes. Buffering non-bottlenecks is less useful, since they usually have to wait for the bottleneck anyway.
What is the lower right-most ISA card?
12 early ISA 8 bit and 16 bit PC network cards. The lower right-most card is an early wireless network card, and the central card with partial beige plastic cover is a PSTN modem.
What is multiqueue NIC?
Multiqueue NICs provide multiple transmit and receive queues, allowing packets received by the NIC to be assigned to one of its receive queues. The NIC may distribute incoming traffic between the receive queues using a hash function. Each receive queue is assigned to a separate interrupt; by routing each of those interrupts to different CPUs or CPU cores, processing of the interrupt requests triggered by the network traffic received by a single NIC can be distributed improving performance.
How does a NIC work?
NICs may use one or more of the following techniques to transfer packet data: 1 Programmed input/output, where the CPU moves the data to or from the NIC to memory. 2 Direct memory access (DMA), where a device other than the CPU assumes control of the system bus to move data to or from the NIC to memory. This removes load from the CPU but requires more logic on the card. In addition, a packet buffer on the NIC may not be required and latency can be reduced.
What is NPAR in NIC?
Some products feature NIC partitioning (NPAR, also known as port partitioning) that uses SR-IOV virtualization to divide a single 10 Gigabit Ethernet NIC into multiple discrete virtual NICs with dedicated bandwidth, which are presented to the firmware and operating system as separate PCI device functions.
What is a NIC controller?
A network interface controller ( NIC, also known as a network interface card, network adapter, LAN adapter or physical network interface, and by similar terms) is a computer hardware component that connects a computer to a computer network. Early network interface controllers were commonly implemented on expansion cards ...
What is receive side scaling?
The hardware-based distribution of the interrupts, described above, is referred to as receive-side scaling (RSS). : 82 Purely software implementations also exist, such as the receive packet steering (RPS) and receive flow steering (RFS). Further performance improvements can be achieved by routing the interrupt requests to the CPUs or cores executing the applications that are the ultimate destinations for network packets that generated the interrupts. This technique improves Locality of reference and results in higher overall performance, reduced latency and better hardware utilization because of the higher utilization of CPU caches and fewer required context switches. Examples of such implementations are the RFS and Intel Flow Director. : 98, 99
What are the two big error counters?
The two big error counters that we are concerned are rx_crc_errors and rx_over_errors (and in conjunction, rx_missed_errors/rx_fifo_errors).
What is the CRC in Ethernet?
The sending host computes a cyclic redundancy check (CRC) of the entire Ethernet frame and puts this value in the FCS (frame check sequence) section of the Ethernet frame after the user payload. The intermediate switch then checks this computed value and the destination host to determine if the frame has been corrupted in transit.
What is the port number of iperf test1?
Since iperf-test1 is the receiving iperf VM, I’ve made a note of the port number, which is 33554464 and the name of the vSwitch, which is vSwitch0. If your VM happens to be on a distributed switch, you’ll have an internal vSwitch name such as ‘DvsPortset-0’ and not the normal friendly label it’s given during setup.
Why do virtual NICs have buffers?
Not unlike physical network cards and switches, virtual NICs must have buffers to temporarily store incoming network frames for processing. During periods of very heavy load, the guest may not have the cycles to handle all the incoming frames and the buffer is used to temporarily queue up these frames. If that buffer fills more quickly than it is emptied, the vNIC driver has no choice but to drop additional incoming frames. This is what is known as buffer or ring exhaustion.
Where is RX ring buffering?
In Windows, you can see the RX Ring and buffering settings in the network adapter properties window. Unfortunately, by default the value is just ‘Not Present’ indicating that it’s using the default of the driver.
Can you increase the size of RX ring?
In theory, you can simply increase the RX Ring #1 size, but it’s also possible to boost the Small Rx Buffers that are used for other purposes. From the network adapter properties page, I have increased Rx Ring #1 to 4096 and Small Rx Buffers to 8192.
Can you have multiple RX queues?
As mentioned earlier, you’ll only have one RX queue by default with the VMXNET3 adapter in Windows. To take advantage of multiple queues, you’ll need to enable Receive Side Scaling. Again, this change will likely cause a momentary network ‘blip’ and impact existing TCP sessions. If this is a production VM, be sure to do this during a maintenance window.
Should I increase RX buffers?
The default values are probably sufficient for the vast majority of VM workloads, but if you have a VM exhibiting buffer exhaustion, there is no reason not to boost it up.
Can you check driver statistics from ESXi?
Most Linux distros provide some good driver statistic information, but that may not always be the case. Thankfully, you can also check statistics from ESXi.
